DEVICES AND METHODS FOR RADIOPHARMACEUTICAL SYNTHESIS

A device for synthesizing a radiotracer includes a microfluidic chip having a concentration module configured to concentrate and capture a radioactive reagent from a radioactive regent mixture, a reaction chamber in fluidic communication with the concentration module and configured to synthesize a radiotracer by reaction of the concentrated radioactive reagent and a radiotracer precursor therein, and a purification module in fluidic communication with the reactor chamber and configured to purify the synthesized radiotracer. The device also includes a heating means positioned in relation to the microfluidic chip for heating the microfluidic chip during evaporation and reaction; and a first valve fluidically coupled with the concentration module and the reaction chamber and a second valve fluidically coupled with the reaction chamber and the purification module for operably controlling transit of various substances or mixtures among the concentration module, the reaction chamber and the purification module.

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Description
CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims priority to and the benefit of U.S. Provisional Patent Application Ser. No. 62/830,678, filed Apr. 8, 2019, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The invention relates generally to radiopharmaceutical synthesis, and more particularly to devices and methods for rapid and efficient production of radiotracer [18F]fallypride.

BACKGROUND INFORMATION

The background description provided herein is for the purpose of generally presenting the context of the invention. The subject matter discussed in the background of the invention section should not be assumed to be prior art merely as a result of its mention in the background of the invention section. Similarly, a problem mentioned in the background of the invention section or associated with the subject matter of the background of the invention section should not be assumed to have been previously recognized in the prior art. The subject matter in the background of the invention section merely represents different approaches, which in and of themselves may also be inventions. Work of the presently named inventors, to the extent it is described in the background of the invention section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the invention.

Non-invasive positron emission tomography (PET) is a valuable medical imaging method that relies on radioactive tracers to monitor specific physiological processes in the body. A radiotracer is a chemical compound with one or more atoms replaced by short-lived positron-emitting radioisotopes, such as 18F or 11C, used to gather physiological information to assess health conditions. The development of PET tracers has been impeded by the enormous infrastructure requirements needed to perform the necessary radioisotope production and subsequent radiochemical reactions that result in the desired radiotracer. Prohibitively large and expensive facilities, such as large-scale automated synthesis modules and “hot cells” widely used for the synthesis of radiopharmaceuticals, thwart the extensive distribution of PET tracers among less-developed but demanding communities. Additionally, due to radioactive decay, the transit time required to move reagents from a PET tracer production site to a clinic limits the flexibility and availability of critical imaging procedures, as a precise schedule involving numerous production facilities, professional technicians and patients must be assured in advance. Typically, the preparation of PET tracers is conducted near the cyclotron producing the radioisotope, which is not necessarily close to the patients requiring the necessary scans. The transit process from production site to imaging clinic results in a significant loss of radioactivity, which is particularly undesired for 11C-type short half-life radiotracers (half-life of 20.2 minutes).

Microfluidic systems have the potential to enable a dose-on-demand (DOD) system of PET tracer distribution, allowing for individual tracer production at the demand of the PET imaging facility. The advantages of microfluidics, including high surface-to-volume ratio, minimized consumption of expensive chemicals and improved thermal exchange and reaction rate, suggest that this platform is particularly well suited for PET tracer production. Several microfluidic approaches pursuing rapid and efficient radiolabeling reactions have been reported in the past decade. Quake et al. first reported multistep synthesis of [18F]FDG based on a multi-layered microfluidic system incorporating on-chip pneumatically-actuated valves for fluid control. While this system reported the production of 190 μCi of [18F]FDG with an impressive radiochemical yield of 38%, the limited capacity of the ion exchange volume significantly hindered the potential for processing more than 2-3 ml of [18F]fluoride mixture, and the multilayer on-chip valve system imposed a high level of complexity on microfluidic device fabrication and integration. Another microfluidic approach using an electrowetting-on-dielectric (EWOD) platform to control droplet movement demonstrated successful synthesis of four different radiotracers. However, the mechanism used for fluoride concentration in that platform limited its ability to handle several ml of the fluoride mixture, as repeatedly loading droplets of fluorine (in hundred-μl volumes) would unavoidably lengthen the overall synthesis time. Also, purification of the synthesized radiotracers was achieved via conventional off-chip processes, which hindered this platform's universality.

Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.

SUMMARY OF THE INVENTION

In one aspect, the invention relates to a device for synthesizing a radiotracer. In one embodiment, the device includes a microfluidic chip formed of a patterned or etched layer on a substrate, comprising a concentration module, a reaction chamber, and a purification module patterned in the polymer layer. The concentration module is configured to concentrate a radioactive reagent from a radioactive regent mixture. The reaction chamber in fluidic communication with the concentration module is configured to synthesize a radiotracer by reaction of the concentrated radioactive reagent and a radiotracer precursor therein. The purification module in fluidic communication with the reactor chamber is configured to purify the synthesized radiotracer.

The device also includes a heating means positioned in relation to the microfluidic chip for heating the microfluidic chip during evaporation and reaction; and a first valve fluidically coupled with the concentration module and the reaction chamber and a second valve fluidically coupled with the reaction chamber and the purification module for operably controlling transit of various substances or mixtures among the concentration module, the reaction chamber and the purification module.

In one embodiment, the device further includes one or more pumps fluidically coupled with at least one of the first valves and the second valves for operably controlling flow of the various substances or mixtures.

In one embodiment, each of the concentration module and the purification module comprises an inlet, an outlet, a microchannel formed between the inlet and the outlet, and a trapping mechanism formed in the microchannel proximate to the outlet of the microchannel.

In one embodiment, inner walls of the microchannel of at least one of the concentration module and the purification module are coated with an inert layer.

In one embodiment, the microchannel has a length, a width, and a height, wherein the height is a micro-size.

In one embodiment, the length is greater than the width, or the length is equal to or less than the width.

In one embodiment, the microchannel of at least one of the concentration module and the purification module comprises two or more sub-chambers in parallel.

In one embodiment, the microchannel of at least one of the concentration module and the purification module comprises a single chamber with two or more isolated sub-inlets and sub-outlets to yield enhanced packing uniformity.

In one embodiment, the trapping mechanism comprises at least one row of pillars with predefined gaps.

In one embodiment, each of the concentration module and the purification module has columns operably formed of microparticles with desired functionality in the microchannel by the trapping mechanism, for radioactivity concentration or purification, wherein the microparticles are suspended in a solution loaded into the microchannel.

In one embodiment, the microparticles in the microchannel of the concentration module comprise anion exchange beads, and wherein the microparticles in the microchannel of the purification module comprise C18 microparticles.

In one embodiment, each of the concentration module and the purification module has in situ photopolymerized porous monoliths used for the capture and/or purification columns, wherein porosity is optimized to ensure both high capture and low resistance.

In one embodiment, the reaction chamber has a reaction cavity and an evaporation port in fluidic commutation with the reaction cavity, wherein the evaporation port is attached on a top surface of the patterned or etched layer and aligned in a center of the reaction cavity.

In one embodiment, the evaporation port comprises a coned nanoport assembly.

In one embodiment, the heating means comprises a hot plate placed under the microfluidic chip.

In one embodiment, the heating means comprises an on-chip resistive heater and an on-chip resistive temperature detector (RTD) to enable closed-loop control of a reaction temperature in a predefined range.

In one embodiment, the on-chip resistive heater comprises metal electrodes patterned on the substrate, and the on-chip RTD comprises metal electrodes patterned on the substrate proximate to the metal electrodes of the on-chip resistive heater.

In one embodiment, the metal electrodes of the on-chip resistive heater and the metal electrodes of the on-chip RTD are formed of a same metal or different metals.

In one embodiment, the heating means further comprises a protective layer formed over the metallic electrodes of the on-chip resistive heater and the on-chip RTD.

In one embodiment, the device further has a microcontroller configured to read a temperature measured by the on-chip RTD and control a solid state relay (SSR) to rapidly connect or disconnect the on-chip resistive heater from a power supply by using a PID (proportional, integral, differential) library.

In one embodiment, the microcontroller is configured further to control operations of the first and second valves, and the one or more pumps so as to control the transit of various substances or mixtures among the concentration module, the reaction chamber and the purification module.

In one embodiment, the microcontroller is configured such that the operations of the first and second valves, the one or more pumps and/or the heating means are controllable via one or more user interfaces in a computer or a mobile device in a wired or wireless communication.

In one embodiment, the radiotracer is [18F]fallypride, wherein the radioactive reagent is [18F]fluoride and the radiotracer precursor is a fallypride precursor.

In another aspect, the invention relates to a method of synthesizing a radiotracer using the device as disclosed above. In one embodiment, the method includes providing a radioactive regent mixture containing a radioactive reagent; introducing the radioactive regent mixture into the concentration module at a first predetermined loading rate followed by injecting a first amount of air into the concentration module to push all liquid through tubing connection and the concentration module, thereby concentrating and capturing the radioactive reagent inside the concentration module; injecting an eluting solution into the concentration module at a second predetermined loading rate to release the concentrated and captured the radioactive reagent from the concentration module, and directing the released radioactive reagent into the reaction chamber, followed by injecting a second amount of air into the concentration module to push all the remaining radioactive reagent into the reaction chamber; achieving an anhydrous condition in the reaction chamber for fallypride fluorination; injecting a radiotracer precursor mixture containing a radiotracer precursor into the reaction chamber and sealing the reaction chamber immediately to minimize loss of radioactivity during the fluorination process; heating the microfluidic chip at a predetermined temperature for a period of time to synthesize the radiotracer inside the reaction chamber; transferring the synthesized radiotracer from the reaction chamber to the purification module so as to purify the synthesized radiotracer inside the purification module containing monodiperse C18 stationary phase; and injecting an amount of pure ethanol into the purification module to elute the purified radiotracer off the microfluidic chip, and collecting the radiotracer at the outlet of the purification module.

In one embodiment, the method further comprises, prior to transferring the synthesized radiotracer from the reaction chamber to the purification module, loading an amount of DI water into the purification module to fully rinse the C18 gel therein.

In one embodiment, the method further comprises, prior to injecting the amount of pure ethanol into the purification module, loading an amount of DI water the reaction chamber and passed over the reaction chamber to totally remove unreacted radioactive reagent ions therein.

In one embodiment, the step of achieving the anhydrous condition in the reaction chamber comprises heating the microfluidic chip at a first temperature gradient to evaporate water inside the reaction chamber through an evaporation port hole on a top of the reaction chamber; cooling down the microfluidic chip below a boiling point of acetonitrile (MeCN); and loading an amount of anhydrous MeCN into the reaction chamber, and heating the microfluidic chip at a second temperature gradient to completely remove residual moisture inside the reaction chamber. In one embodiment, the first temperature gradient includes heating the microfluidic chip at about 100° C. for about 3 minutes and then at about 120° C. for about 5 minutes, and the second temperature gradient includes heating the microfluidic chip at a second temperature gradient about 85° C. for about 3 minutes, and then at about 120° C. for about 7 minutes.

In one embodiment, the step of achieving the anhydrous condition in the reaction chamber further comprises applying flow of N2 through the reaction camber to facilitate removal of residual moisture inside the reaction chamber during the entire process of achieving the anhydrous condition.

In one embodiment, the liquid coming out from the concentration module contains a negligible amount of radioactivity and is collected in a vial at port fluidically connecting the first valve.

In one embodiment, the radiotracer is [18F]fallypride, wherein the radioactive reagent is [18F]fluoride and the radiotracer precursor is a fallypride precursor.

In one embodiment, the eluting solution comprises a K222/K2CO3 solution.

In one embodiment, the radioactive regent mixture contains the radioactive reagent of [18F]fluoride in [18O]-enriched water.

In one embodiment, the radiotracer precursor mixture contains the radiotracer precursor of fallypride dissolved in dimethyl sulfoxide (DMSO).

These and other aspects of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the following drawings, although variations and modifications therein may be affected without departing from the spirit and scope of the novel concepts of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate one or more embodiments of the invention and, together with the written description, serve to explain the principles of the invention. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like elements of an embodiment.

FIG. 1 shows synthesis process for the production of [18F]fallypride, according to one embodiment of the invention.

FIG. 2A shows a photograph of the microfluidic chip according to one embodiment of the invention, with an American twenty-five cent coin placed above.

FIG. 2B shows a schematic illustration of the microfluidic chip employed for [18F]fallypride production, including a [18F]fluoride concentration column, fluorination reaction cavity and [18F]fallypride purification column, according to one embodiment of the invention.

FIG. 2C shows a photograph of anion exchange beads trapped inside a microchannel by about 10 μm gap PDMS pillars, according to one embodiment of the invention.

FIG. 2D shows a photograph of reverse phase C18 microparticles trapped inside a microchannel with about 40 μm gap PDMS pillars, according to one embodiment of the invention.

FIGS. 3A-3F shows a schematic representation of the steps used for the production of [18F]fallypride on the integrated microfluidic chip, according to one embodiment of the invention. The six steps shown are: (FIG. 3A) concentrate [18F]fluoride using anion-exchange column, (FIG. 3B) release trapped [18F]fluoride off the column and transfer into reaction cavity, (FIG. 3C) evaporate to achieve an anhydrous environment by heating and N2 drying, (FIG. 3D) [18F]fallypride fluorination, (FIG. 3E) isolate undesired products using purification column, and (FIG. 3F) collect purified [18F]fallypride off chip.

FIG. 4 shows the relationship between precursor concentration and fluorination efficiency, according to one embodiment of the invention.

FIG. 5A shows crude radio-HPLC of [18F]fallypride synthesized inside the reaction cavity, according to one embodiment of the invention.

FIG. 5B shows radio-HPLC of [18F]fallypride eluted from the on-chip purification column, according to one embodiment of the invention.

FIG. 6A shows PET image of rat brain using [18F]fallypride produced in a microfluidic chip, according to one embodiment of the invention.

FIG. 6B shows the variation of [18F]fallypride concentration imaged in the microPET for 2 hours, according to one embodiment of the invention.

FIG. 7A-7B are photographs of on-chip reaction cavity with no reagent inside (FIG. 7A) and after water evaporation (FIG. 7B), according to one embodiment of the invention.

FIG. 8 shows a radio-HPLC analysis of the waste mixture passed through the C18 column, according to one embodiment of the invention. This injection was taken using the mixture solution flowing out from the purification column after labelling reaction. 95% [18F]fluoride was washed off the purification column, and only 5% [18F]fallypride was lost at this step.

FIG. 9 shows an UV spectrum for the purified [18F]fallypride, according to one embodiment of the invention, showing product peak at 11.11 min. The presence of minor impurities is observed throughout the spectrum.

FIGS. 10A-10D show on-chip RTD and heater according to one embodiment of the invention. FIG. 10A is an image of the on-chip heater and RTD. FIG. 10B shows a microcontroller and associated hardware (MAX31865 and SSR) for providing PID-based closed-loop control of local temperature. FIGS. 10C and 10D are respectively IR thermal and regular optical images of the on-chip heater and RTD in operation.

FIGS. 11A-11D show on-chip packed bed designs that enhance the flow rate according to embodiments of the invention. FIG. 11A is a packed bed geometry as disclosed in EXAMPLE 1, with frit at the bottom. FIG. 11B is an alternative embodiment that has an equivalent volume as that of FIG. 11A, but shorter and wider to reduce fluidic resistance. FIG. 11C shows a architecture having three smaller chambers in parallel, leading to reduced fluidic resistance but more uniformity in each chamber. FIG. 11D shows a single chamber with three isolated inlets and outlets to yield enhanced packing uniformity and avoid unequal pressure between chambers. Arrows indicate differences between architectures of FIGS. 11C and 11D.

FIG. 12A shows fluidic resistance measurements for the design shown in FIG. 11A and the branching connected design shown in FIG. 11B of approximately equivalent volume of packed beads according to embodiments of the invention.

FIGS. 12B and 12C are low magnification images of FIG. 11A and 11B channel designs packed with SCX resin according to embodiments of the invention.

 DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout.

The terms used in this specification generally have their ordinary meanings in the art, within the context of the invention, and in the specific context where each term is used. Certain terms that are used to describe the invention are discussed below, or elsewhere in the specification, to provide additional guidance to the practitioner regarding the description of the invention. For convenience, certain terms may be highlighted, for example using italics and/or quotation marks. The use of highlighting and/or capital letters has no influence on the scope and meaning of a term; the scope and meaning of a term are the same, in the same context, whether or not it is highlighted and/or in capital letters. It will be appreciated that the same thing can be said in more than one way. Consequently, alternative language and synonyms may be used for any one or more of the terms discussed herein, nor is any special significance to be placed upon whether or not a term is elaborated or discussed herein. Synonyms for certain terms are provided. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification, including examples of any terms discussed herein, is illustrative only and in no way limits the scope and meaning of the invention or of any exemplified term. Likewise, the invention is not limited to various embodiments given in this specification.

It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below can be termed a second element, component, region, layer or section without departing from the teachings of the invention.

It will be understood that when an element is referred to as being “on,” “attached” to, “connected” to, “coupled” with, “contacting,” etc., another element, it can be directly on, attached to, connected to, coupled with or contacting the other element or intervening elements may also be present. In contrast, when an element is referred to as being, for example, “directly on,” “directly attached” to, “directly connected” to, “directly coupled” with or “directly contacting” another element, there are no intervening elements present. It will also be appreciated by those of skill in the art that references to a structure or feature that is disposed “adjacent” to another feature may have portions that overlap or underlie the adjacent feature.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” or “has” and/or “having” when used in this specification specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

Furthermore, relative terms, such as “lower” or “bottom” and “upper” or “top,” may be used herein to describe one element's relationship to another element as illustrated in the figures. It will be understood that relative terms are intended to encompass different orientations of the device in addition to the orientation shown in the figures. For example, if the device in one of the figures is turned over, elements described as being on the “lower” side of other elements would then be oriented on the “upper” sides of the other elements. The exemplary term “lower” can, therefore, encompass both an orientation of lower and upper, depending on the particular orientation of the figure. Similarly, if the device in one of the figures is turned over, elements described as “below” or “beneath” other elements would then be oriented “above” the other elements. The exemplary terms “below” or “beneath” can, therefore, encompass both an orientation of above and below.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present invention, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

As used herein, “around,” “about,” “substantially” or “approximately” shall generally mean within 20 percent, preferably within 10 percent, and more preferably within 5 percent of a given value or range. Numerical quantities given herein are approximate, meaning that the terms “around,” “about,” “substantially” or “approximately” can be inferred if not expressly stated.

As used herein, the terms “comprise” or “comprising,” “include” or “including,” “carry” or “carrying,” “has/have” or “having,” “contain” or “containing,” “involve” or “involving” and the like are to be understood to be open-ended, i.e., to mean including but not limited to.

As used in this invention, the phrase “at least one of A, B, and C” should be construed to mean a logical (A or B or C), using a non-exclusive logical OR. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

The description below is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. The broad teachings of the invention can be implemented in a variety of forms. Therefore, while this invention includes particular examples, the true scope of the invention should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the invention.

Positron Emission Tomography (PET) is a non-invasive imaging modality that allows for the in vivo quantification of biochemical processes using radiolabeled compounds or “tracers”. These tracers typically undergo synthesis using an automated synthesis module (ASM) that requires an infrastructural link to a cyclotron, a lead-shielded fume hood known as a hot cell, and a large amount of precious laboratory real estate. These requirements have created a bottleneck in PET tracer development, leading a search for a new type of system that can decrease system costs while increasing radiochemical and chemical purities, specific activities, and/or radiochemical yields of the final tracer.

Microfluidic systems have the potential to enable a dose-on-demand (DOD) system of PET tracer distribution, allowing for individual tracer production at the demand of the PET imaging facility. This has the potential to decrease the cost of the tracer and enable the increase of specialized PET tracer production. The first human use of a [18F]fallypride tracer produced by a microfluidic batch-reactor has been reported recently. However, while this recent report did use a microfluidic chip as microreactor for the fluorination step, the fluoride concentration subsystem utilized a commercial ion-exchange cartridge (off-chip), and final purification step was accomplished via conventional HPLC (also off-chip), thereby missing the opportunity of integrating all steps of the production within a single, compact microfluidic chip. Although there has been exciting progress employing microfluidic technology for PET tracer synthesis, most efforts focus primarily on the investigation of a single step in the process (mostly on-chip radiosynthesis), leaving other essential steps, such as concentration of the [18F]fluoride mixture and radiotracer product purification, to be performed off-chip.

To address the aforementioned deficiencies and inadequacies, one aspect of this invention is to integrate all the essential modules onto a single microfluidic chip, enabling the synthesis of PET tracer from the very beginning (radioactive [18F]fluoride mixture) to the final stage (radiotracer ready for injection). The goals of this highly-integrated microfluidic platform would include the following: (1) The entire production process should be fast and efficient, minimizing the decay of radionuclide and consuming minimal reagents. (2) The shield needed to protect users from radiation on the microfluidic chip should be simply achieved by using lead bricks, avoiding the need for large, bulky hot cells. (3) The microfluidic chip should be low-cost and disposable, and a fresh chip should be used for each individual radiotracer production run. (4) The microfluidic chip should be able to produce purified products in sufficient doses, ready for animal or human imaging. (5) The technique to produce the on-chip columns should be flexible enough to enable the production of various PET radiotracers by simply switching the materials packed inside the microchannel.

To achieve these goals and facilitate the development of novel PET tracers for both research and clinical applications, in certain embodiments, a simple microfluidic system is disclosed, which integrates several modules on a single chip to accomplish all principal steps for radiotracer production. To demonstrate the utility of this microfluidic chip, [18F]fallypride, a widely used radiotracer in PET imaging, is synthesized starting with [18F]fluoride retrieved from a nearby cyclotron shown in FIG. 1. Instead of relying on complicated on-chip flow control components that require multiple levels of lithography and feature alignment (e.g., elastomer valves formed via aligned multilayer PDMS), the invention in some embodiments employs simple off-chip mechanical valves to provide convenient and reliable control of reagent transfer between various modules. The invention also uses an on-chip ion-exchange column that is capable of concentrating a quantity of fluoride sufficient for several human doses. In some embodiments, the invention employs an on-chip cavity that facilitates rapid drying and enables subsequent fluorination reaction. However, unlike previous efforts where HPLC or commercial C18 cartridges were utilized for purification of the final product, the invention employs an on-chip C18 column that is integrated with the previous modules. It is noteworthy that the microfluidic chip, incorporating all the on-chip modules for [18F]fallypride radiotracer production, is low-cost and disposable, allowing an operator to use a fresh chip for each on-demand PET radiotracer production run. The flow control elements, e.g., but are not limited to, syringe pumps and mechanical valves, can be easily cleaned using ethanol or other appropriate solvents and are thus reusable. Using this microfluidic device, a small shielded space composed of several lead bricks would satisfy the requirements for radiation shielding, eliminating the need for a standard hot cell. Moreover, further automation of the pumps and valves could accelerate the entire process and shorten the overall synthesis time period, minimizing the loss of imaging reagents due to the decay of radionuclides. Variation of either the solid phase extraction (SPE) material or the elution methodology could allow our microfluidic platform to produce additional radiotracers. To adapt this microfluidic chip to a clinical setting, further development of the purification method is also required to achieve sufficient chemical purity. With excellent throughput, radiochemical purity and disposability, the invented microfluidic system represents a viable means to facilitate the production of radio-tracers on demand and promote both the distribution and use of PET technology.

In one aspect of the invention, a device for synthesizing a radiotracer is provided.

In one embodiment, the device includes a microfluidic chip formed of a patterned or etched layer on a substrate, comprising a concentration module, a reaction chamber, and a purification module patterned in the polymer layer. The concentration module is configured to concentrate and capture a radioactive reagent from a radioactive regent mixture. The reaction chamber in fluidic communication with the concentration module is configured to synthesize a radiotracer by reaction of the concentrated radioactive reagent and a radiotracer precursor therein. The purification module in fluidic communication with the reactor chamber is configured to purify the synthesized radiotracer.

The device also includes a heating means positioned in relation to the microfluidic chip for heating the microfluidic chip during evaporation and reaction; and a first valve fluidically coupled with the concentration module and the reaction chamber and a second valve fluidically coupled with the reaction chamber and the purification module for operably controlling transit of various substances or mixtures among the concentration module, the reaction chamber and the purification module.

In one embodiment, the device further includes one or more pumps fluidically coupled with at least one of the first valves and the second valves for operably controlling flow of the various substances or mixtures.

In one embodiment, each of the concentration module and the purification module comprises an inlet, an outlet, a microchannel formed between the inlet and the outlet, and a trapping mechanism formed in the microchannel proximate to the outlet of the microchannel.

In one embodiment, inner walls of the microchannel of at least one of the concentration module and the purification module are coated with an inert layer.

In one embodiment, the microchannel has a length, a width, and a height, wherein the height is a micro-size. In one embodiment, the length is greater than the width, or the length is equal to or less than the width.

In one embodiment, the microchannel of at least one of the concentration module and the purification module comprises two or more sub-chambers in parallel.

In one embodiment, the microchannel of at least one of the concentration module and the purification module comprises a single chamber with two or more isolated sub-inlets and sub-outlets to yield enhanced packing uniformity.

In one embodiment, the trapping mechanism comprises at least one row of pillars with predefined gaps.

In one embodiment, each of the concentration module and the purification module has columns operably formed of microparticles with desired functionality in the microchannel by the trapping mechanism, for radioactivity concentration or purification, wherein the microparticles are suspended in a solution loaded into the microchannel.

In one embodiment, the microparticles in the microchannel of the concentration module comprise anion exchange resins/beads, and wherein the microparticles in the microchannel of the purification module comprise C18 microparticles.

In one embodiment, each of the concentration module and the purification module has in situ photopolymerized porous monoliths used for the capture and/or purification columns, wherein porosity is optimized to ensure both high capture and low resistance.

In one embodiment, the reaction chamber has a reaction cavity and an evaporation port in fluidic commutation with the reaction cavity, wherein the evaporation port is attached on a top surface of the patterned or etched layer and aligned in a center of the reaction cavity.

In one embodiment, the evaporation port comprises a coned nanoport assembly.

In one embodiment, the heating means comprises a hot plate placed under the microfluidic chip.

In one embodiment, the heating means comprises an on-chip resistive heater and an on-chip resistive temperature detector (RTD) to enable closed-loop control of a reaction temperature in a predefined range.

In one embodiment, the on-chip resistive heater comprises metal electrodes of heating patterned on the substrate, and the on-chip RTD comprises metal electrodes of temperature detecting patterned on the substrate proximate to the metal traces of the on-chip resistive heater.

In one embodiment, the metal electrodes of the on-chip resistive heater and the metal electrodes of the on-chip RTD are formed of a same metal or different metals.

In one embodiment, the heating means further comprises a protective layer formed over the metallic electrodes of the on-chip resistive heater and the on-chip RTD.

In one embodiment, the device further has a microcontroller configured to read a temperature measured by the on-chip RTD and control a solid state relay (SSR) to rapidly connect or disconnect the on-chip resistive heater from a power supply by using a PID (proportional, integral, differential) library.

In one embodiment, the microcontroller is configured further to control operations of the first and second valves, and the one or more pumps so as to control the transit of various substances or mixtures among the concentration module, the reaction chamber and the purification module.

In one embodiment, the microcontroller is configured such that the operations of the first and second valves, the one or more pumps and/or the heating means are controllable via one or more user interfaces in a computer or a mobile device in a wired or wireless communication.

In one embodiment, the radiotracer is [18F]fallypride, wherein the radioactive reagent is [18F]fluoride and the radiotracer precursor is a fallypride precursor.

In another aspect of the invention, a method of synthesizing a radiotracer using the device as disclosed above is also proved.

In one embodiment, the method includes providing a radioactive regent mixture containing a radioactive reagent; introducing the radioactive regent mixture into the concentration module at a first predetermined loading rate followed by injecting a first amount of air into the concentration module to push all liquid through tubing connection and the concentration module, thereby concentrating and capturing the radioactive reagent inside the concentration module; injecting an eluting solution into the concentration module at a second predetermined loading rate to release the concentrated and captured the radioactive reagent from the concentration module, and directing the released radioactive reagent into the reaction chamber, followed by injecting a second amount of air into the concentration module to push all the remaining radioactive reagent into the reaction chamber; achieving an anhydrous condition in the reaction chamber for fallypride fluorination; injecting a radiotracer precursor mixture containing a radiotracer precursor into the reaction chamber and sealing the reaction chamber immediately to minimize loss of radioactivity during the fluorination process; heating the microfluidic chip at a predetermined temperature for a period of time to synthesize the radiotracer inside the reaction chamber; transferring the synthesized radiotracer from the reaction chamber to the purification module so as to purify the synthesized radiotracer inside the purification module containing monodiperse C18 stationary phase; and injecting an amount of pure ethanol into the purification module to elute the purified radiotracer off the microfluidic chip, and collecting the radiotracer at the outlet of the purification module.

In one embodiment, the method further comprises, prior to transferring the synthesized radiotracer from the reaction chamber to the purification module, loading an amount of DI water into the purification module to fully rinse the C18 gel therein.

In one embodiment, the method further comprises, prior to injecting the amount of pure ethanol into the purification module, loading an amount of DI water the reaction chamber and passed over the reaction chamber to totally remove unreacted radioactive reagent ions therein.

In one embodiment, the step of achieving the anhydrous condition in the reaction chamber comprises heating the microfluidic chip at a first temperature gradient to evaporate water inside the reaction chamber through an evaporation port hole on a top of the reaction chamber; cooling down the microfluidic chip below a boiling point of acetonitrile (MeCN); and loading an amount of anhydrous MeCN into the reaction chamber, and heating the microfluidic chip at a second temperature gradient to completely remove residual moisture inside the reaction chamber. In one embodiment, the first temperature gradient includes heating the microfluidic chip at about 100° C. for about 3 minutes and then at about 120° C. for about 5 minutes, and the second temperature gradient includes heating the microfluidic chip at a second temperature gradient about 85° C. for about 3 minutes, and then at about 120° C. for about 7 minutes.

In one embodiment, the step of achieving the anhydrous condition in the reaction chamber further comprises applying flow of N2 through the reaction camber to facilitate removal of residual moisture inside the reaction chamber during the entire process of achieving the anhydrous condition.

In one embodiment, the liquid coming out from the concentration module contains a negligible amount of radioactivity and is collected in a vial at port fluidically connecting the first valve.

In one embodiment, the radiotracer is [18F]fallypride, wherein the radioactive reagent is [18F]fluoride and the radiotracer precursor is a fallypride precursor.

In one embodiment, the eluting solution comprises a K222/K2CO3 solution.

In one embodiment, the radioactive regent mixture contains the radioactive reagent of [18F]fluoride in [18O]-enriched water.

In one embodiment, the radiotracer precursor mixture contains the radiotracer precursor of fallypride dissolved in dimethyl sulfoxide (DMSO).

These and other aspects of the present invention are further described below. Without intent to limit the scope of the invention, exemplary instruments, apparatus, methods and their related results according to the embodiments of the present invention are given below. Note that titles or subtitles may be used in the examples for convenience of a reader, which in no way should limit the scope of the invention. Moreover, certain theories are proposed and disclosed herein; however, in no way they, whether they are right or wrong, should limit the scope of the invention so long as the invention is practiced according to the invention without regard for any particular theory or scheme of action.

EXAMPLE 1 Microfluidic Platform for Rapid and Efficient Production of Radiotracer [18F]Fallypride Device Fabrication

In this exemplary example, a microfluidic device, “RAPID” (Radiopharmaceuticals As Precision Imaging Diagnostics) platform/system, is developed. The RAPID platform utilizes a polydimethylsiloxane (PDMS) microfluidic chip with a chamber microreactor that is used to produce the tracer [18F]fallypride of sufficient quality for PET imaging, where reaction processes occur on-chip with reagent delivery reliant on off-chip syringe pumps and valves. The RAPID platform is constructed using PDMS and borosilicate glass, and each of the three main steps for [18F]fallypride production has a designated area, i.e., a designated module. [18F]Fluoride trapping and release is located in a designated concentration column filled with an ion exchange resin/beads with trapping and release of the fluoride controlled by the solvent. The chamber microreactor (reaction cavity) is a small hole covered with a thin PDMS layer to enable fast and reliable solvent evaporation without the loss of radiation. Following the reaction, the reaction products are run through a C18 column (purification column) to initiate purification, allowing for the removal of some reaction byproducts and unreacted [18F]fluoride.

Specifically, the microchannel pattern is fabricated using facilities within the cleanroom affiliated with the Vanderbilt Institute of Nanoscale Science and Engineering (VINSE). A laser writer (Heidelberg μPG 101) is utilized to create patterns on a silicon wafer using an about 60 μm thick layer of mr-DWL 40 resist. Then, liquid PDMS (Sylgard 184, part A and part B mixed in 10:1 ratio and degassed) is poured onto the resist-patterned silicon wafer located in a petri dish to produce an about 1 cm thick layer. After curing in an oven (Thermo Scientific Lindberg/Blue M) at about 65° C. for about 12 h, the PDMS layer is peeled off the resist mold, and holes are punched at the inlet and outlet of the microchannels using an about 1.5 mm internal diameter punch (Ted Pella). The patterned PDMS layer, along with a substrate such as a glass microscope slide (Fisher Scientific, Premium Plain Glass Microscope Slides), is exposed to an oxygen plasma (Harrick Plasma, PDC-001) for about 60 seconds. Then, the two plasma-treated surfaces are bonded together and baked on a hot plate at about 60° C. for about 1 h before use. Next, the top surface of the microfluidic chip and an about 0.2 mm thick PDMS film with an about 1.5 mm size hole in the center are plasma treated again. The PDMS film is aligned such that the hole on the PDMS film is located at the center of a reaction cavity, and subsequently bonded to the top of the reaction cavity. A coned NanoPort assembly (IDEX, N-333) is aligned and placed on the top of the PDMS layer. Well-mixed PDMS is used as an adhesive and applied on the edge of the coned assembly, and then baked in an oven at about 65° C. for about 2 hours, such that the NanoPort is firmly attached to the top of the PDMS film. The microbore tubing (about 0.02″ ID and about 0.06″ OD) is purchased from Cole-Parmer and inserted directly into the PDMS layer without using any tubing connectors. The average length of tubing used between the chip and the external valves is about 5 cm. In all experiments, the microfluidic chip, hot plate and syringe pump are set inside a hot cell and the syringe is switched and reconnected for loading different reagents and N2 behind the hot cell.

In this exemplary embodiment, the microfluidic chip is formed of a patterned PDMS layer on a glass slide/substrate. It should be appreciated that the microfluidic chip can be formed of any suitable materials, for example, a patterned layer on the top of a non-patterned polymer layer/substrate or a non-patterned glass slide/substrate, or an etched glass slide on the top of a non-patterned polymer layer/substrate or a non-patterned glass slide/substrate. The polymer can be any polymer in addition to PDMS.

FIGS. 2A-2D show a schematic illustration and images of the microfluidic chip used for fallypride synthesis according to some embodiments of the invention. As shown in FIGS. 2A-2B, the microfluidic chip device includes three main modules: a concentration column (module), a fluorination reaction cavity (chamber) and a purification column (module) that serve to concentrate the diluted [18F]fluoride mixture, perform the heat-assisted fallypride fluorination reaction and purify the synthesized [18F]fallypride, respectively.

In some exemplary embodiments, the on-chip concentration column (i.e., concentration module) is about 5 mm in width, about 10 mm in length and about 60 μm in height. Anion exchange beads (Source 15Q, GE healthcare) are packed into the concentration column by introducing an about 20% ethanol solution containing suspended beads into the concentration microchannel through the inlet of the concentration microchannel. The desired quantity (about 3 μl) of anion exchange beads is trapped by a double or triple row of square PDMS pillars with about 10 μm gap near the outlet of the concentration microchannel to form the desired column therein, as shown in FIG. 2C of a photograph of anion exchange beads trapped inside the concentration microchannel by about 10 μm gap PDMS pillars. It should be appreciated that the pillars can be any geometric shape such as rhombus, rectangle, circle, and so on. Then, the anion exchange beads are activated using about 1.0 M of KHCO3 (potassium hydrogen carbonate, about 0.2 ml) followed by flushing with about 0.5 ml DI water (18 MCI, Milli-Q Integral ultrapure water).

In some exemplary embodiments, the central reaction cavity (i.e., reaction chamber) is fabricated using an about 8 mm inner diameter punch (Ted Pella). The coned NanoPort assembly (IDEX, N-333) is placed on the top of the PDMS layer and aligned with the punch thereon. As the microfluidic chip device has an about 1 cm thick PDMS top layer, the maximum volume allowed inside the reaction cavity is about 500 μl.

In some exemplary embodiments, the fallypride purification column (i.e., purification module) is prepared using the same technique used to form the concentration column, inserting a triple row of square PDMS pillars with about 40 μm gap near the outlet of the purification microchannel. Silica gel (Fisher Scientific, Acros Organics, size 40-63 μm), suspended in pure ethanol, is introduced through the inlet of the purification microchannel, and is trapped inside to form the desired column. The dimension of the fallypride purification column is about 4.8 cm in length, about 4 mm in width and about 60 μm in height, allowing about 7.2 μl (about 20 mg) silica gel to be packed inside. The purification column is activated before the experiment by flowing about 0.5 ml DI water through it. FIG. 2D is a photograph showing reverse phase C18 microparticles trapped inside the purification microchannel with the square PDMS pillars with about 40 μm gap.

In some exemplary embodiments, off-chip mechanical valves, e.g., valves A and B (Upchurch Valves, V-100D), as shown in FIGS. 2A-2B, are used to control the transit of reagents among these three modules. A syringe pump (New Era Pump Systems, NE-300, not shown herein) is used to control flow of the various reagents. A hot plate (IKA, Control-VISC), as shown in FIG. 2A, placed under the microfluidic chip is used to heat the entire device during solvent evaporation and fluorination reaction steps.

In other embodiments, on-chip valves such as on-chip rotary planar valves (RPV), and/or on-chip pump such as on-chip rotary planar peristaltic micropump (RPPM) can also be utilized to control the transit of reagents among these three modules, and flow of the various reagents.

Reagents and Materials

In the exemplary examples, [18F]Fluoride ion was obtained by cyclotron (GE Healthcare PETtrace 880) irradiation of [18O]-enriched water. Anhydrous acetonitrile (MeCN, about 99.8%), anhydrous methanol (MeOH, about 99.8%) were purchased from Sigma Aldrich and used without further purification. Fallypride precursor was purchased from ABX Chemicals (Dresden, Germany). K222/K2CO3 eluting solutions was prepared in the mixture of about 250 mg of K222 dissolved in about 6 ml acetonitrile and about 140 mg of K2CO3 in DI water. All experiments were performed in compliance with the Vanderbilt University Medical Center policy on animal use and ethics, and complied with the relevant national/international guidelines (AAALAC-accredidation, United States). These studies were approved by the Vanderbilt Institutional Care and Use Committee (IACUC).

Analytical Facilities

In the exemplary examples, a Hitachi HPLC (LaChrom Elite, Pump L-2130) equipped with a wavelength UV detector (L-2400) and inline radiation detector (Inline Carroll & Ramsey) was used for radiochemical analysis. A Phenomenex C18 column (Luna 5 μm C18(2) 100 Å LC Column 250×4.6 mm) was utilized and the flow rate of isocratic mobile phase of about 55% ethanol and about 45% 15 mM Na2PO4 buffer was about 0.9 ml/min. Total radioactivity was measured using calibrated dose calibrators (Capintec, CRC-25PET).

Microfluidic Chip Operation

FIGS. 3A-3F illustrates the steps for fallypride radiosynthesis on the microfluidic chip according to some embodiments of the invention. Radioactive [18F]fluoride in [18O]-enriched water was obtained immediately after cyclotron irradiation. Unless noted elsewhere, the amount of radioactivity used in in these exemplary experiments was about 30 mCi in about 0.1 ml irradiated target wash water. As shown in FIG. 3A, the [18F]fluoride mixture was introduced into the inlet of the on-chip concentration column using the syringe pump with an about 30 μl/min loading rate followed by about 0.1 ml of air at a loading rate of about 50 μl/min allowing all liquid to be pushed through the tubing connection and the concentration column. The liquid coming out from the concentration column was collected in a glass vial at port PA2 fluidically connecting valve A, and typically contained a negligible amount of radioactivity (less than about 2 μCi), i.e., waste. The radioactivity of the initial [18F]fluoride loading, captured inside the concentration column, and the [18F]fluoride residue left in the syringe were measured separately via a dose calibrator. The efficiency of the concentration column was calculated after accounting for the decay of the radioisotope.

To release the captured [18F]fluoride inside the concentration column, about 75 μl of K222/K2CO3 eluting solution was injected into the inlet of the concentration column at an about 30 μl/min loading rate, as shown in FIG. 3B. At the same time, the mechanical valve A, fluidically connected between the concentration column and the reaction cavity (batch reactor), was set to direct the released reagent into the reaction cavity. Another 0.1 ml air was injected from the inlet of the concentration column to push all the remaining liquid into the reaction cavity. Because the fluorination reaction requires anhydrous conditions shown in FIG. 3C, the microfluidic chip was first placed on a hot plate at about 100° C. for about 3 minutes and then at about 120° C. for about 5 minutes. The heated water inside the reaction cavity evaporated through the about 1.5 mm hole on the top. The microfluidic chip was then removed from the hot plate for about 2 minutes, allowing the entire chip to cool down below the boiling point of acetonitrile. To completely remove residual moisture inside the reaction cavity, about 75 μl anhydrous acetonitrile (MeCN) was loaded from the inlet (denoted as PA1 in FIG. 3A) of the reaction cavity and the entire microfluidic chip was placed on another hotplate at about 85° C. for about 3 minutes, and then at about 120° C. for about 7 minutes. Constant N2 flow at about 0.2 psi was applied through the inlet (via port PA1 of valve A) of the reaction cavity to facilitate the removal of residual moisture during the entire evaporation process. After these drying steps, solid residue was observed at the bottom of the reaction cavity (FIG. 7B). The on-chip radioactivity after evaporation was measured and the loss of radioactivity was less than about 5%.

After achieving the anhydrous conditions necessary for fallypride fluorination, about 0.1 ml dimethyl sulfoxide (DMSO) containing fallypride precursor (about 3 mg), vortex-mixed for about 30 minutes in advance, was injected from the inlet (via port PA1 of valve A) of the reaction cavity and the reaction cavity was immediately sealed by screwing in a male nut (Fisher Scientific) into the NanoPort, minimizing the loss of radioactivity during the fluorination process. As shown in FIG. 3D, the microfluidic chip was heated at about 100° C. for about 10 minutes to produce the radioactive fallypride. The successful synthesis of [18F]fallypride was validated via radio-HPLC analysis, the radioactive peak eluting at about 11˜12 minutes matching the reference standard.

To obtain chemically pure [18F]fallypride suitable for PET imaging, the crude production material was purified using a column containing monodiperse C18 stationary phase. Before transferring all liquid through the on-chip purification column, about 0.1 ml DI water was loaded from the inlet (via port PB1 of valve B) of the purification column to fully rinse the C18 gel. Subsequently, valve A was closed and the valve B was open, creating unidirectional flow from the reaction cavity to the purification column, as shown in FIG. 3E. The flow rate produced by the syringe pump was about 50 μl/min. The tight seal of the reaction cavity provided by the male nut allowed the synthesized compound to be injected into the purification column without leakage. Undesired compounds, including unreacted fallypride precursor, any remaining [18F]fluoride, and various by-products were thereby pushed off-chip, only leaving the desired [18F]fallypride trapped on-chip. Next, as shown in FIG. 3E, another 1 ml DI water was loaded from the inlet (via port PA1 of valve A) of the reaction chamber and passed over the reaction chamber to totally remove unreacted [18F]fluoride ion, which would lower the overall radiochemical purity and confound imaging procedures. Finally, trapped [18F]fallypride was eluted off of the chip using about 0.1 ml pure ethanol and collected in a glass vial at the outlet of the purification column, as shown in FIG. 3F.

Results and Discussions

[18F]Fluoride Concentration: According to the invention, to synthesize [18F]fallypride or other radiotracers with the microfluidic chip, the first critical step is to concentrate [18F]fluoride that is provided as a diluted solution in [18O]-enriched water. In this exemplary study, PDMS pillars are employed to form physical barriers near the end (outlet) of the concentration microchannel, thus trapping desired anion exchange microparticles inside the concentration column. FIG. 2C shows an optical image of anion exchange beads packed inside the concentration column. Experimental results listed in Table 1 suggested that the on-chip concentration column can accomplish efficient enrichment of a sufficient quantity of [18F]fluoride with minimal radioactivity loss, comparable or better than performance achieved with a commonly used purification cartridge (Waters Sep-Pak QMA).

TABLE 1 The relationship between the volume of anion exchange beads inside the concentration column and the radioactivity trapped on the microfluidic chip. All listed values are decay corrected to the time point of initial radioactivity in the syringe. Initial syringe Final syringe Waste vial Radioactivity Volume of radioactivity radioactivity radioactivity trapped on beads (μl) (mCi) (mCi) (mCi) chip (mCi) Efficiency 0.62 10.3 0.6 0.9 8.93 90.1% 0.62 8.7 0.6 0.7 7.5 92.2% 0.62 35.8 1.8 12.6 21.5   65% 0.62 39.1 1.5 14.3 20.9 59.7% 3 95.7 0.34 0.01 93.0 97.7% 3 128.6 4.8 0.1 123.0 95.9%

As expected, the maximum quantity of [18F]fluoride that is captured by the concentration column was related to the volume of anion exchange beads packed inside the microchannel. Considering that the goal of the microfluidic chip is to synthesize multiple doses of radiotracer sufficient for human imaging, the on-chip concentration module, must be capable of capturing radioactivity in the range of about 100 mCi (3700 MBq). To determine the relationship between the volume of anion exchange resins and the captured radioisotope, several versions of ion exchange columns with varying dimensions were fabricated. Raw [18F]fluoride with radioactivity values as high as about 130 mCi (4810 MBq) was then loaded into each column to evaluate the trapping efficiency and determine the optimal dimension. Table 2 shown in FIG. 11 summarizes the results of these exemplary experiments. It turned out that about 3 μl (about 10 mg) of anion exchange resin captured over about 100 mCi [18F]fluoride with the efficiency near about 98% over a loading period of about 6 minutes. However, a reduced timespan may be achieved with additional optimization of column geometry (i.e., wider microchannel) to allow higher reagent loading rate.

Solvent Exchange: To release the captured [18F]fluoride from the concentration column, about 75 μl of K222/K2CO3 solution was introduced into the anion exchange column channel, after which the released solution was directed to the reaction cavity. During reagent transfer process, valve A and valve B were set in the fashion shown in FIG. 3B to minimize the liquid stuck in the tubing connection. In the attempt to reduce the overall synthesis time, the volume of K222/K2CO3 eluting solution required to fully release all [18F]fluoride off the concentration column was optimized. In this system, a large portion of the production time is devoted to achieving a completely anhydrous state prior to the synthesis reaction, and thus optimizing the volume of eluting solution helps promote the overall production efficiency and minimizes the decay of radioisotope. The release efficiency with various volumes was compared and the results indicated that about 75 μl of the K222/K2CO3 was the optimal amount for releasing [18F]fluoride with radioactivity loss less than about 5%, as listed in Table 2.

TABLE 2 The relationship between the volume of K222/K2CO3 used for releasing trapped off the concentration column and the releasing efficiency. The efficiency [18F]fluoride is calculated accounting for the decay of the radionuclide over time. Volume On-chip Released radioactivity of K222 radioactivity radioactivity left on-chip (μl) (mCi) (mCi) (mCi) Efficiency 50 7.5 4.8 1.7 74% 50 4.6 3.58 0.94 77% 75 4.25 3.84 0.23 95% 100 6.2 5.48 0.1 98%

To achieve anhydrous conditions inside the reaction cavity, the entire chip was placed on a hotplate and a temperature gradient (about 100° C. for about 3 minutes and about 120° C. for about 5 minutes) was set, instead of direct heating at extremely high temperature, to avoid violent boiling, which could result in the liquid splashing out from the upper hole. A slow nitrogen flow was introduced via the inlet (via port PA1 of valve A) of the reaction cavity (FIG. 3C) to facilitate the evaporation process. After the first round of heating, azeotropic distillation was employed by injecting about 75 μl anhydrous MeCN into the reaction cavity (FIG. 3C) to completely remove any remaining moisture. In conventional macroscopic radiotracer production, 2-3 cycles of azeotropic distillation are typically performed to guarantee an anhydrous environment. In contrast, using the microfluidic platform according to the invention, only one cycle of azeotropic distillation is sufficient to enable the subsequent nucleophilic substitution reactions, thus shortening the required production timeframe. FIGS. 7A-7B are photographs of the on-chip reaction cavity with no reagent inside (FIG. 7A) and after water evaporation (FIG. 7B), where the solid salt was deposited on the bottom of the reaction cavity after evaporation.

Fluorination Reaction: The fluorination reaction is performed after introducing the fallypride precursor (FIG. 3D), dissolved in a polar aprotic solvent, into the reaction cavity containing the concentrated, dried fluoride-kryptofix complex. Instead of employing a low-boiling-point solvent, such as acetonitrile, the fallypride precursor was dissolved in dimethyl sulfoxide (DMSO) and loaded into the reaction cavity. Though acetonitrile has been widely used in clinical production and has the benefit of being easily removed later, the required temperature for nucleophilic substitution reactions with [18F]fluoride (usually around 100° C.), exceeds the boiling point of acetonitrile, which would increase the pressure inside the sealed cavity and possibly lead to leakage. Employing the high boiling point solvent DMSO avoids these issues. Based on a report by Javed et al., the concentration of fallypride precursor plays a significant role in final crude radiochemical yield in a batch microfluidic reactor. To optimize the yield of [18F]fallypride in the microfluidic chip according to the invention, the relationship between the concentration of fallypride precursor and the overall conversion efficiency was further investigated. Similar to previous reports, a rise of fluorination efficiency was observed as the concentration of fallypride precursor increases, as shown in FIG. 4. The successful synthesis of [18F]fallypride was confirmed via HPLC analysis (FIG. 5A). The result indicated that the labeling efficiency during fluorination process was about 87%, higher than what can be typically obtained using conventional automated methodologies.

[18F]Fallypride Purification: After the fluorination reaction, the product exists in a solution containing unwanted quantities of unreacted [18F]fluoride, K222, and other undesired byproducts. Thus, the crude [18F]fallypride mixture must be purified. This is accomplish using an integrated on-chip purification column. The purification column was fabricated in a manner identical to the concentration column. FIG. 2D shows an optical image of silica gel packed inside the purification microchannel forming the purification column. After the fluorination reaction, the hot microfluidic chip was allowed to cool down to approximately room temperature. Meanwhile, 0.1 ml DI water was loaded through the purification column to fully activate the reverse phase C18 (FIG. 3D). Next, 1 ml DI water was injected at the inlet of the reaction cavity (FIG. 3E), pushing the reacted solution (with the products in DMSO) through the purification column. To minimize any potential loss of [18F]fallypride, the volume ratio of DMSO to water was tuned to 1:10 such that it was able to carry all crude radiochemical mixture in the reaction cavity but did not wash the captured [18F]fallypride off the on-chip purification column. HPLC analysis of the outlet waste indicated negligible [18F]fallypride loss during this step (FIG. 8). Finally, the trapped [18F]fallypride was released by injecting about 0.1 ml pure ethanol into the inlet of purification column. FIG. 5B shows radio-HPLC analysis of the eluted [18F]fallypride, which exhibited 100% radiopurity.

The overall radiochemical yield (RCY) (10±3%, n=5) is calculated as the ratio of the decay-corrected radioactivity of the resulting [18F]fallypride released off the chip, divided by the initial radioactivity of [18F]fluoride loaded into the microfluidic chip (trapped by the on-chip concentration column). The radioactivity of the [18F]fluoride loaded into the microfluidic chip was measured by placing the whole chip in a dose calibrator. The average radioactivity used for those productions was about 50 mCi and the volume of anion exchange beads and reverse phase C18 was about 3.2 μl and about 7.2 μl, respectively. The whole process was completed in approximately 60 minutes starting from the loading of [18F]fluoride to the collecting of purified [18F]fallypride, which could likely be further shortened using automated external valves and programmable syringe pumps. As reported by Elizarov, PDMS may react with [18F]fluoride ions, which might reduce the overall radiochemical yield. To reduce this loss, in certain embodiments, the inner walls of the microchannels are coated with an inert layer, and in another embodiments, the chip fabrication material is modified.

To further verify the utility of the resulting [18F]fallypride, we produced (using the integrated microfluidic chip) a dose of about 300 μCi with about 19.55 Ci/μmol (723.35 GBq/μmol) of specific activity and about 98.62% of radiochemical purity, and obtained PET data from a rat brain. The time point used to calculate the specific activity was at the end of production, namely the time when the purified [18F]fallypride was retrieved from chip. The rat was brought to the imaging lab to habituate about 3 hours prior to imaging. Sbout 0.1 ml purified [18F] fallypride was filtered through an about 0.45 μm filter (Millex-HV) and about 0.9 ml saline was added to formulate the PET probe used for rat injection. FIG. 6A shows PET images of rat brain using [18F]fallypride produced in a microfluidic chip, and FIG. 6B shows the variation of [18F]fallypride concentration imaged in the microPET for about 2 hours. The accumulation and pharmacokinetics of [18F]fallypride were as expected when evaluated in the rat brain. A typical UV spectrum, indicating some observable chemical impurities, is given in FIG. 9. Though the chemical purity has been dramatically improved from the crude product mixture, further purification is needed.

A general performance comparison to previously reported results from other platforms (including information regarding fluorination efficiency, purification method, synthesis time, resulting dose amount, specific activity and overall radiochemical yield) is summarized in Table 3. The invented microfluidic platform exhibits comparable performance in terms of fluorination efficiency and specific activity. Further optimization and automation of various operational parameters may increase the overall radiochemical yield and reduce the entire synthesis time.

TABLE 3 Operational performances of our microfluidic platform compared to several reported results based on microfluidic [18F]fallypride production. All efficiencies and yields are calculated based on decay-corrected values Publication Lu et al. Chen et al. Lebedev et al. This invention Starting 0.5-2.5 mCi Not reported 370 mCi About 50 mCi [18F]fluoride Fluorination Up to 88% 65 ± 11% Not reported 80 ± 08% efficiency (n = 6) (n = 4) Purification HPLC No HPLC On-chip method module Dose amount 0.5-1.5 mCi Not reported About 27 mCi About 3 mCi Specific activity Not Reported 19 Ci μmol−1 Not Reported 19.55 Ci μmol−1 Overall RCY Not reported Not Reported 37 ± 5% 10 ± 3% Synthesis time About 50 min About 31 min About 45 min About 60 min PET imaging No No Human Rat

In terms of disposability, the microfluidic chip may be discarded after each PET tracer production once any residual on-chip radioactivity has decayed to a safe level. Off-chip flow control components, such as pumps and mechanical valves, may be cleaned using ethanol or other appropriate solvents, and are thus reusable.

In some embodiments, a heating and fluid flow control system (micro-controller, solenoid valves, remote control pump system, etc.) are fully automated, which enables PET probe production to run without the need for operator intervention at every step.

Briefly, in this exemplary example, a simple, economic and efficient microfluidic platform to aid both radiochemistry research efforts and clinical efforts by rapidly producing ultrapure radioactive fallypride on demand. This highly integrated configuration enables all essential steps needed for [18F]fallypride production without any off-chip treatment, starting from reaction reagents and ending with a purified product. These disposable chips may allow high throughput investigations of novel radiotracer chemistry, as well as the mass-production of established PET tracers. By using this microfluidic device, we envision that clinicians may overcome a significant bottleneck imposed by limited access to an onsite cyclotron, as they could easily utilize delivered radionuclides and produce imaging reagents as needed without relying on centralized facilities. The integration of this microfluidic device within current clinical environments would be a relatively straightforward task, and serve as a solution to the high cost of standard radiopharmaceutical production. Though further development of the purification method for [18F]fallypride is still needed, replacing packing materials inside each column may make this microfluidic platform suitable for the production of other PET tracers.

EXAMPLE 2 Microfluidic Platform with Enhanced Reproducibility via on-Chip Heating

In this exemplary example, certain engineering approaches are employed to enhance the reproducibility and ease-of-use of the RAPID platform by employing an integrated on-chip heater and resistive temperature detector (RTD) to enable closed-loop control of reaction temperature to better than +/−1° C.

Specifically, using standard photolithographic techniques, a resistive heater composed of platinum is patterned on a microscope slide. During the same process, a RTD, such as, but not limited to, a platinum RTD that is the most common type of RTD and often called P100 or P1000 depending on 0° C. resistance, is produced near the heater. FIG. 10A is an image of the on-chip heater and RTD. All traces are formed of platinum having a thickness of about 300 nm. To avoid contact between the metallic traces of the heater and RTD and the reactants to be heated, a thin layer of silica (about 50 nm) is deposited by sputtering with regions away from the heater and RTD masks to prevent deposition and enable electrical contact. In operation, the heater controllably heats the local chip temperature (on a microscope slide) to about 90° C., as demonstrated in FIGS. 10C-10D being respectively IR thermal and regular optical images of the on-chip heater and RTD in operation.

In addition, a microcontroller (e.g., but not limited to, NodeMCU board using an ESP8266 microcontroller chip with WiFi interface) is employed to read the temperature measured by the RTD (e.g., but not limited to, using the MAX31865 RTD sensor interface) and control a solid state relay (SSR) to rapidly connect or disconnect the on-chip heater from a power supply by using a well-established PID (proportional, integral, differential) library (a common approach to achieve tight process control). FIG. 10B shows one embodiment of such a microcontroller and associated hardware (MAX31865 and SSR) for providing PID-based closed-loop control of local temperature. Such architecture ensures to both control the temperature within about 1° C. and enable a wireless interface via a mobile device such as a smartphone.

To validate the performance of the on-chip heater and closed-loop control, a slab of PDMS with a hole punched out from the center (to form a reservoir) is placed on the microscope slide over the heater and RTD. The reservoir is filled with about 500 μL H2O. The control circuit is set to maintain the water at various temperatures (e.g., 60, 70, 80° C.) and the temperature profile as measured by the RTD recorded. To demonstrate temperatures above 100° C., dimethylsulfoxide (DMSO, boiling point of 189° C.) is used. Once the temperature has reached the steady state, an IR thermometer (FLIR One Pro) is used to validate the temperature of the water in the reservoir. Consistent offsets and any other calibration issues can be easily accounted for by the PID algorithm and associated software. The PID algorithm is tuned (i.e., the P, I, and D gain values determined) by a standard autotuning algorithm (part of the PID library).

The reservoir of about 500 μL water can be controllably heated to a specific temperature using a closed loop control algorithm, in a range (for water) of about 35-90° C. with a tolerance of better than +/−1° C. Given the small thermal mass and local heating, the time required to heat from room temperature to the desired setpoint is less than about 60 seconds. The heating system is capable of maintaining this level of control up to at least 130° C. (as tested using DMSO).

It is possible that rapid, localized heating of the microfluidic device may cause the microscope slide on which it is formed to crack due to thermal shock. In this case, one can either slow the heating rate or pattern a larger heater to achieve a more uniform temperature profile across the entire glass slide, which will not impact any of the on-chip radiochemistry. In addition, if the silica protective layer proves problematic (cracking, pinholes, poor uniformity, poor adherence to the substrate), the device can be coated with parylene to prevent contact between the water and the metallic traces. Alternatively, a thin film of PDMS can be spin-coated over the metallic electrodes, and a micropatterned PDMS slab is bonded to that surface. In either case, masking is again used to prevent coating regions of the device (far from the heater and RTD) to be used for electrical contact. In some embodiments, these passivation layers may need to be reduced in thickness to allow better heat transfer between the heater/RTD and the liquid in the reservoir. Moreover, the microfluidic devices can be placed on a Peltier unit to heat (and cool) the chips as needed.

EXAMPLE 3 Different Microfluidic Architectures for High Throughput Radiofluorination

While the above-disclosed [18F]-radiochemistry device demonstrates impressive on-demand [18F]Fallypride production capabilities, there are still several engineering hurdles that must be overcome to enable the RAPID platform/system to be used in the clinic for on-demand human dosage production of tracers with 18F chemistries. This exemplary study addresses the engineering limitations of the RAPID device to form a platform that is fast, reproducible, and can produce clinically relevant quantities of two important 18F-based tracers in a ready-to-use format.

As disclosed above, the on-chip packed beds are used to capture over about 100 mCi of 18F with over 95% efficiency, and release it with over 98% efficiency (starting with about 6.2 mCi captured). The flow rates used, however, were relatively small at about 30-50 μL/min, due to the high fluidic resistance of the packed beds and resulting pressures required, which led to capture and elution timeframes on the order of about 10 minutes, far too long for the envisioned high throughput production of multiple unique tracers achieved with this platform. To enable rapid processing of large quantities of radionuclide and precursors, several microfluidic architectures are implemented by utilizing two benchmarks: amount of radionuclide processed (i.e., amount of radioactivity) and speed with which a standard dosage can be produced (starting from radionuclide and precursor in separate vials, and ending with a ready-to-use product). As shown in FIGS. 11A-11D illustrating different architectures/embodiments of on-chip packed beds, each microfluidic architecture contains an equivalent mass of resin to determine which one provides the best combination of low fluidic resistance, high capture capability, and narrow band elution of captured concentrated radionuclide. FIG. 11A is a packed bed geometry as disclosed above, with frit at the bottom. FIG. 11B is an alternative embodiment that has an equivalent volume as that of FIG. 11A, but shorter and wider to reduce fluidic resistance. The concern here would be with uniform bead packing. FIG. 11C shows a architecture having three smaller chambers in parallel, leading to reduced fluidic resistance but more uniformity in each chamber. FIG. 11D shows a single chamber with three isolated inlets and outlets to yield enhanced packing uniformity and avoid unequal pressure between chambers. Arrows indicate differences between architectures of FIGS. 11C-11D.

Fluidic resistance through each architecture is modeled using COMSOL and pore size and porosity of the packed beds are predicted. The results of these models using pressure (e.g., Honeywell 26PC flow through pressure sensor and Omega strain meter) and flow (e.g., Sensirion USB-interface flow-meter) meters to quantify fluidic resistance are experimentally validated, as shown in FIG. 12A. In some embodiments, chambers are packed with Maxi-Clean SCX resin (about 600 mg, particle size about 50 μm) by introducing suspensions in ethanol (about 5% w/v) at about 100 μl/min. After conditioning, capture and release uniformity are characterized using about 10 μM solution of Rhodamine B (in DI water) and fluorescence microscopy (to observe spatial variations in capture and ability to elute a narrow band of dye in about 100 μL of ethanol eluting solution) to determine the optimum design. The top three designs, as determined by low fluidic resistance, good trapping uniformity and high capture capability, uniform release in a narrow band, are subsequently packed with anion exchange resin (e.g., Source 15Q, GE healthcare) as described above and tested with [18F]fluoride in [18O]-enriched water from the cyclotron facility at VUMC. The fluidic architecture that functions best, as determined by lowest fluidic resistance while still capable of trapping at least 25 mCi and releasing at least 98% of the trapped activity in about 100 μL of eluting solution, is employed for all on-chip preconcentration columns. Similar processes are employed for on-chip purification columns as well. FIG. 12A is fluidic resistance measurements for the design shown in FIG. 11A and the branching connected design shown in FIG. 11B of approximately equivalent volume of packed beads. Pressure was measured at several flow rates and data was fit with a linear model to extract flow resistance. As fluidic resistance in a short, wide rectangular microchannel scales roughly as Length/Width, and the branching connected bed of FIG. 11B is three-time shorter and three-time wider than the design of FIG. 11A, one would expect a roughly 9-fold decrease in resistance. Experimentally, a 13-fold decrease in resistance was measured, which is not overly dissimilar from the predicted behavior. FIGS. 12B-12C are low magnification images of FIGS. 11A-11B channel designs packed with SCX resin.

For the optimized packed beds, a reduced preconcentration time less than 1 minute is required for to trap and release at least 25 mCi of 18F. The pressures required to achieve this performance is less than 15 PSI. The same concepts used to reduce fluidic resistance in the on-chip preconcentration column is employed for on-chip purification columns and similarly enable high purification performance combined with high flow rates (and thus short timeframes).

Alternatively, in some embodiments, in situ photopolymerized porous monoliths are used for the capture and/or purification columns, where porosity is optimized (e.g., by appropriate choice of porogens and monolith chemistry) to ensure both high capture and low resistance. Another route towards achieving higher flow rates and thus higher throughput is the ability to use higher pressure with these microfluidic devices. PDMS sealed to glass is capable of withstanding pressures up to about 70 PSI with appropriate plasma surface treatments. Instead of glass, silanized PMMA is used in some embodiments to roughly double the device failure pressure, where thermal bonding of embossed PMMA substrates yields an even higher bond strength. In addition, residence time is not a bottleneck in the process.

In sum, the invention provides, among other things, a simple, high throughput and efficient microfluidic system for synthesizing radioactive [18F]fallypride, a PET imaging radiotracer widely used in medical imaging. The microfluidic chip contains all essential modules required for the synthesis and purification of the radioactive fallypride. The radiochemical yield of the tracer is sufficient for multiple animal injections for preclinical imaging studies. To produce the on-chip concentration and purification columns, in certain embodiments of the invention, a “trapping” mechanism is employed by inserting rows of square pillars with predefined gaps near the outlet of microchannel. Microspheres with appropriate functionality are suspended in solution and loaded into the microchannels to form columns for radioactivity concentration and product purification. Instead of relying on complicated flow control elements (e.g., micromechanical valves requiring complex external pneumatic actuation), external valves are utilized to control transfer of the reagents between different modules according to the invention. The on-chip ion exchange column can efficiently capture [18F]fluoride with negligible loss (about 98% trapping efficiency), and subsequently release a burst of concentrated [18F]fluoride to the reaction cavity. In certain embodiments, a thin layer of PDMS with a small hole in the center facilitates rapid and reliable water evaporation (with the aid of azeotropic distillation and nitrogen flow) while reducing fluoride loss. During the solvent exchange and fluorination reaction, the entire chip is uniformly heated to the desired temperature using a hot plate. All aspects of the [18F]fallypride synthesis are monitored by high-performance liquid chromatography (HPLC) analysis, resulting in labelling efficiency in fluorination reaction ranging from about 67% to about 87% (n=5). Moreover, after isolating unreacted [18F]fluoride, remaining fallypride precursor, and various by-products via an on-chip purification column, the eluted [18F]fallypride is radiochemically pure and of a sufficient quantity to allow for PET imaging (about 5 mCi). In one embodiment, a PET image of a rat brain injected with about 300 μCi [18F]fallypride produced by the microfluidic chip is obtained, demonstrating the utility of the product produced by the microfluidic reactor. With a short synthesis time (about 60 min) and a highly integrated on-chip modular configuration that allows for concentration, reaction, and product purification, the microfluidic chip offers numerous exciting advantages with the potential for applications in radiochemical research and clinical production. Moreover, due to its simplicity and potential for automation, it can be easily integrated into a clinical environment. In addition, to enhance the reproducibility and ease-of-use of the RAPID platform, an integrated on-chip heater and resistive temperature detector (RTD) are employed to enable closed-loop control of reaction temperature to better than +/−1° C. Further, different microfluidic architectures for high throughput radiofluorination are also disclosed.

The foregoing description of the exemplary embodiments of the invention has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching.

The embodiments were chosen and described in order to explain the principles of the invention and their practical application so as to activate others skilled in the art to utilize the invention and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the invention pertains without departing from its spirit and scope. Accordingly, the scope of the invention is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.

Some references, which may include patents, patent applications, and various publications, are cited and discussed in the description of the invention. The citation and/or discussion of such references is provided merely to clarify the description of the invention and is not an admission that any such reference is “prior art” to the invention described herein. All references cited and discussed in this specification are incorporated herein by reference in their entireties and to the same extent as if each reference was individually incorporated by reference.

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doi:10.1117/12.2049526.

Claims

1. A device for synthesizing a radiotracer, comprising:

(a) a microfluidic chip formed of a patterned or etched layer on a substrate, comprising a concentration module, a reaction chamber, and a purification module patterned in the polymer layer, wherein the concentration module is configured to concentrate a radioactive reagent from a radioactive regent mixture; the reaction chamber in fluidic communication with the concentration module is configured to synthesize a radiotracer by reaction of the concentrated radioactive reagent and a radiotracer precursor therein; and the purification module in fluidic communication with the reactor chamber is configured to purify the synthesized radiotracer;
(b) a heating means positioned in relation to the microfluidic chip for heating the microfluidic chip during evaporation and reaction; and
(c) a first valve fluidically coupled with the concentration module and the reaction chamber and a second valve fluidically coupled with the reaction chamber and the purification module for operably controlling transit of various substances or mixtures among the concentration module, the reaction chamber and the purification module.

2. The device of claim 1, further comprising one or more pumps fluidically coupled with at least one of the first valves and the second valves for operably controlling flow of the various substances or mixtures.

3. The device of claim 1, wherein each of the concentration module and the purification module comprises an inlet, an outlet, a microchannel formed between the inlet and the outlet, and a trapping mechanism formed in the microchannel proximate to the outlet of the microchannel.

4. The device of claim 3, wherein inner walls of the microchannel of at least one of the concentration module and the purification module are coated with an inert layer.

5. The device of claim 3, wherein the microchannel has a length, a width, and a height, wherein the height is a micro-size.

6. The device of claim 3, wherein the length is greater than the width, or the length is equal to or less than the width.

7. The device of claim 3, wherein the microchannel of at least one of the concentration module and the purification module comprises two or more sub-chambers in parallel.

8. The device of claim 3, wherein the microchannel of at least one of the concentration module and the purification module comprises a single chamber with two or more isolated sub-inlets and sub-outlets to yield enhanced packing uniformity.

9. The device of claim 3, wherein the trapping mechanism comprises at least one row of pillars with predefined gaps.

10. The device of claim 3, wherein each of the concentration module and the purification module has columns operably formed of microparticles with desired functionality in the microchannel by the trapping mechanism, for radioactivity concentration or purification, wherein the microparticles are suspended in a solution loaded into the microchannel.

11. The device of claim 10, wherein the microparticles in the microchannel of the concentration module comprise anion exchange beads, and wherein the microparticles in the microchannel of the purification module comprise C18 microparticles.

12. The device of claim 3, wherein each of the concentration module and the purification module has in situ photopolymerized porous monoliths used for the capture and/or purification columns, wherein porosity is optimized to ensure both high capture and low resistance.

13. The device of claim 1, wherein the reaction chamber has a reaction cavity and an evaporation port in fluidic commutation with the reaction cavity, wherein the evaporation port is attached on a top surface of the patterned or etched layer and aligned in a center of the reaction cavity.

14. The device of claim 13, wherein the evaporation port comprises a coned nanoport assembly.

15. The device of claim 1, wherein the heating means comprises a hot plate placed under the microfluidic chip.

16. The device of claim 1, wherein the heating means comprises an on-chip resistive heater and an on-chip resistive temperature detector (RTD) to enable closed-loop control of a reaction temperature in a predefined range.

17. The device of claim 16, wherein the on-chip resistive heater comprises metal electrodes patterned on the substrate, and the on-chip RTD comprises metal electrodes patterned on the substrate proximate to the metal electrodes of the on-chip resistive heater.

18. The device of claim 17, wherein the metal electrodes of the on-chip resistive heater and the metal electrodes of the on-chip RTD are formed of a same metal or different metals.

19. The device of claim 17, wherein the heating means further comprises a protective layer formed over the metallic electrodes of the on-chip resistive heater and the on-chip RTD.

20. The device of claim 16, further comprising a microcontroller configured to read a temperature measured by the on-chip RTD and control a solid state relay (SSR) to rapidly connect or disconnect the on-chip resistive heater from a power supply by using a PID (proportional, integral, differential) library.

21. The device of claim 20, wherein the microcontroller is configured further to control operations of the first and second valves and the one or more pumps so as to control the transit of various substances or mixtures among the concentration module, the reaction chamber and the purification module.

22. The device of claim 21, wherein the microcontroller is configured such that the operations of the first and second valves, the one or more pumps and/or the heating means are controllable via one or more user interfaces in a computer or a mobile device in a wired or wireless communication.

23. The device of claim 1, wherein the radiotracer is [18F]fallypride, wherein the radioactive reagent is [18F]fluoride and the radiotracer precursor is a fallypride precursor.

24. A method of synthesizing a radiotracer using the device of claim 1, comprising

providing a radioactive regent mixture containing a radioactive reagent;
introducing the radioactive regent mixture into the concentration module at a first predetermined loading rate followed by injecting a first amount of air into the concentration module to push all liquid through tubing connection and the concentration module, thereby concentrating and capturing the radioactive reagent inside the concentration module;
injecting an eluting solution into the concentration module at a second predetermined loading rate to release the concentrated and captured the radioactive reagent from the concentration module, and directing the released radioactive reagent into the reaction chamber, followed by injecting a second amount of air into the concentration module to push all the remaining radioactive reagent into the reaction chamber;
achieving an anhydrous condition in the reaction chamber for fallypride fluorination;
injecting a radiotracer precursor mixture containing a radiotracer precursor into the reaction chamber and sealing the reaction chamber immediately to minimize loss of radioactivity during the fluorination process;
heating the microfluidic chip at a predetermined temperature for a period of time to synthesize the radiotracer inside the reaction chamber;
transferring the synthesized radiotracer from the reaction chamber to the purification module so as to purify the synthesized radiotracer inside the purification module containing monodiperse C18 stationary phase; and
injecting an amount of pure ethanol into the purification module to elute the purified radiotracer off the microfluidic chip, and collecting the radiotracer at the outlet of the purification module.

25. The method of claim 24, further comprising, prior to transferring the synthesized radiotracer from the reaction chamber to the purification module, loading an amount of DI water into the purification module to fully rinse the C18 gel therein.

26. The method of claim 24, further comprising, prior to injecting the amount of pure ethanol into the purification module, loading an amount of DI water the reaction chamber and passed over the reaction chamber to totally remove unreacted radioactive reagent ions therein.

27. The method of claim 24, wherein the step of achieving the anhydrous condition in the reaction chamber comprises:

heating the microfluidic chip at a first temperature gradient to evaporate water inside the reaction chamber through an evaporation port hole on a top of the reaction chamber;
cooling down the microfluidic chip below a boiling point of acetonitrile (MeCN); and
loading an amount of anhydrous MeCN into the reaction chamber, and heating the microfluidic chip at a second temperature gradient to completely remove residual moisture inside the reaction chamber.

28. The method of claim 27, wherein the first temperature gradient includes heating the microfluidic chip at about 100° C. for about 3 minutes and then at about 120° C. for about 5 minutes, and wherein the second temperature gradient includes heating the microfluidic chip at a second temperature gradient about 85° C. for about 3 minutes, and then at about 120° C. for about 7 minutes.

29. The method of claim 27, wherein the step of achieving the anhydrous condition in the reaction chamber further comprises:

applying flow of N2 through the reaction camber to facilitate removal of residual moisture inside the reaction chamber during the entire process of achieving the anhydrous condition.

30. The method of claim 24, wherein the liquid coming out from the concentration module contains a negligible amount of radioactivity and is collected in a vial at port fluidically connecting the first valve.

31. The method of claim 24, wherein the radiotracer is [18F]fallypride, wherein the radioactive reagent is [18F]fluoride and the radiotracer precursor is a fallypride precursor.

32. The method of claim 31, wherein the eluting solution comprises a K222/K2CO3 solution.

33. The method of claim 31, wherein the radioactive regent mixture contains the radioactive reagent of [18F]fluoride in [18O]-enriched water.

34. The method of claim 31, wherein the radiotracer precursor mixture contains the radiotracer precursor of fallypride dissolved in dimethyl sulfoxide (DMSO).

Patent History
Publication number: 20200316230
Type: Application
Filed: Apr 7, 2020
Publication Date: Oct 8, 2020
Inventors: H. Charles Manning (Franklin, TN), Michael L. Nickels (Nashville, TN), Xin Zhang (Nashville, TN), Leon M. Bellan (Nashville, TN)
Application Number: 16/841,965
Classifications
International Classification: A61K 51/04 (20060101); B01J 19/00 (20060101);