Abstract: Provided herein is a stabilized oxygen transport matrix that includes a reversible oxygen binding protein, such as hemoglobin, immobilized throughout the stabilized oxygen transport matrix. The stabilized oxygen transport matrix is used to transport oxygen and can be used as an oxygen transport region and a reaction region of an analyte sensor, such as an implantable glucose sensor. The reversible binding protein can also function as an oxygen probe within the analyte sensor.

Abstract: Described herein are systems and methods for distinguishing between a control solution and a blood sample. In one aspect, the methods include using a test strip in which multiple current transients are measured by a meter electrically connected to an electrochemical test strip. The current transients are used to determine if a sample is a blood sample or a control solution based on at least two characteristics. Further described herein are methods for calculating a discrimination criteria based upon at least two characteristics. Still further described herein are system for distinguishing between blood samples and control solutions.

Abstract: A nanoparticle translocation device includes a first reservoir having a first reservoir electrode, a second reservoir having a second reservoir electrode, and at least one nanopore providing fluid communication between the first and second reservoirs. The device also includes one or more inner electrode portions on an inner wall of the nanopore and one or more outer electrode portions disposed on an outer wall of the nanopore. The device further includes at least one DC voltage supply for selectively applying a DC voltage to each of the first reservoir electrode, the second reservoir electrode, and the outer electrode layer, where the inner electrode portions, the outer electrode portions, and the nanopore are in a substantially coaxial arrangement.

Abstract: The present disclosure relates generally to an electrochemical sensor comprising a membrane layer comprising one or both of an active enzymatic portion and an inactive-enzymatic or non-enzymatic portion, at least one electrode disposed beneath the membrane and either at least one pH sensor or a hematocrit sensor. The present disclosure also relates to methods of adjusting analyte concentration values using a correction factor based on measured pH values and/or measured hematocrit levels.

Abstract: The present disclosure relates generally to an electrochemical sensor comprising a membrane layer comprising one or both of an active enzymatic portion and an inactive-enzymatic or non-enzymatic portion, at least one electrode disposed beneath the membrane and either at least one pH sensor or a hematocrit sensor. The present disclosure also relates to methods of adjusting analyte concentration values using a correction factor based on measured pH values and/or measured hematocrit levels.

Abstract: The present invention provides a method of electrochemically measuring a hematocrit (Hct) value using a sensor, capable of achieving excellent measurement accuracy and reliability and also provides a sensor used in the method. The method of electrochemically measuring a hematocrit (Hct) value of blood include: providing an electrode system having a working electrode (11) and a counter electrode (12), in which a redox substance is provided on the counter electrode (12) but not on the working electrode (11); supplying blood to the electrode system; applying a voltage to the electrode system in this state to cause an oxidation current or a reduction current to flow between the working electrode (11) and the counter electrode (12); detecting the oxidation current or the reduction current; and determining a Hct value based on a value of the detected current.

Abstract: A biosensor system determines an analyte concentration of a biological sample using an electrochemical process without Cottrell decay. The biosensor system generates an output signal having a transient decay, where the output signal is not inversely proportional to the square root of the time. The transient decay is greater or less than the ?0.5 decay constant of a Cottrell decay. The transient decay may result from a relatively short incubation period, relatively small sample reservoir volumes, relatively small distances between electrode surfaces and the lid of the sensor strip, and/or relatively short excitations in relation to the average initial thickness of the reagent layer. The biosensor system determines the analyte concentration from the output signal having a transient decay.

Abstract: A method of determining concentrations of a plurality of analytes from a single blood sample placed in a single opening. A portion of the single blood sample is absorbed by a test matrix that includes a plurality of layers and a chromogenic agent. A colored response is generated by the test matrix. The colored response is proportional to the concentration of a first analyte. A portion of the single blood sample is drawn into a capillary tube and placed in contact with an electrode and a counter-electrode. An electrical property of the single blood sample is analyzed through the electrode and counter-electrode. The electrical property is proportional to the concentration of a second analyte in the single blood sample.

Abstract: Described herein are systems and methods for distinguishing between a control solution and a blood sample. In one aspect, the methods include using a test strip in which multiple current transients are measured by a meter electrically connected to an electrochemical test strip. The current transients are used to determine if a sample is a blood sample or a control solution based on at least two characteristics. Further described herein are methods for calculating a discrimination criteria based upon at least two characteristics. Still further described herein are system for distinguishing between blood samples and control solutions.

Abstract: The invention relates to sensors configured to include compositions disposed in specific regions of the sensor in order to provide the sensors with enhanced functional properties, for example faster start-up times. These compositions include, for example, hygroscopic compositions, gas generating compositions and gas solvating compositions. While typical embodiments of the invention pertain to glucose sensors, the systems, methods and materials disclosed herein can be adapted for use with a wide variety of sensors known in the art.

Abstract: The disclosure provides for reagent compositions for biosensors comprising release polymers, methods of making such biosensors and films of reagent compositions comprising release polymers. The reagent compositions comprise a release polymer and an effective analyte detecting amount of an enzyme an enzyme cofactor and a redox compound capable of acting in a biosensor as (i) a redox mediator associated with a working electrode (ii) a redox couple associated with a reference electrode or (iii) the redox mediator associated with the working electrode and the redox couple for the reference electrode.

Abstract: A detection method for a sensor membrane formed of EuTixOy as part of a biosensor by using PNIPAAm for wrapping enzymes is provided with adding 1.0 g of NIPAAm powder to 20 ml water, heating same at 60° C. to form NIPAAm solution, and cooling the NIPAAm solution; adding 200 ?l of 98.7 wt % of APS and 50 ?l of 99 wt % of TEMED to the NIPAAm solution, uniformly mixing same, and reacting the mixture for 30 hours to prepare a transparent, gel PNIPAAm; adding 5 mg enzymes to 100 ?l of 1× PBS buffer solution, uniformly mixing same, adding 100 ?l of PNIPAAm to the buffer solution, and uniformly mixing the buffer solution; placing a biosensor on a heater for heating at a constant temperature of 37° C. wherein the biosensor is an EIS sensor having a sensor membrane formed of EuTixOy; and taking a measurement.

Abstract: The present invention relates to an analyzer (1) to be used with an analytical tool (2) mounted thereto and used for analyzing a particular component contained in a sample supplied to the analytical tool (2). The analyzer (1) includes at least one detection terminal pair (11, 12) including a first and a second detection terminals (11A, 11B, 12A, 12B) which are capable of selecting a mutually contacting state and a non-contacting state, a detector (15) for detecting the state of contact of the first and the second detection terminals (11A, 11B, 12A, 12B), and an abnormality detector (16) for detecting an abnormality of the at least one detection terminal pair (11, 12) based on the detection result by the detector (15).

Abstract: Accordingly, the present invention provides a method of forming an electrode having reduced corrosion and water decomposition on a surface thereof. A substrate which has a conductive layer disposed thereon is provided and the conductive layer has an oxide layer with an exposed surface. The exposed surface of the oxide layer contacts a solution of an organic surface active compound in an organic solvent to form a protective layer of the organic surface active compound over the oxide layer. The protective layer has a thickness of from about 0.5 nm to about 5 nm and ranges therebetween depending on a chemical structure of the surface active compound.

Abstract: Disclosed relates to an electrochemical determination system of glycated proteins, the system comprising: a filtering means for filtering labeled compounds bound to glycated proteins and non-glycated proteins after adding labeling compounds, capable of selectively binding to the glycated proteins to a solution, in which glycated/non-glycated proteins coexist, to be bound all to the glycated proteins; and a quantifying means for quantifying the filtered labeling compounds, not bound to the glycated proteins. The system of the present invention filters the residual labeled compounds left after binding to glycated proteins to quantify, instead of directly quantifying glycated proteins via the known glycated protein determination methods, thus simplifying the configuration of the system that can provide exact determinations with a low cost.

Abstract: A cellular electrophysiological measurement device includes a thin plate and a frame. The thin plate has a first surface with a depression and a second surface with a through-hole. The frame is in contact with an outer periphery on the second surface of thin plate. The thin plate has a laminated structure of at least two layers including a first material layer on the first surface and a second material layer on the second surface. The frame is formed of a third material layer. The structure allows the cellular electrophysiological measurement device to be not so vulnerable to breakage of thin plate and other damages, thereby having high production yield.

Abstract: An adhesive composition for use in devices and methods for measuring a presence or a concentration of a particular component, such as an antigen, in a sample, such as blood, are provided. In one exemplary embodiment of an adhesive composition, the composition includes an adhesive, water, a poloxamer, and an anticoagulant. The adhesive can include particular properties, such as being hydrophilic, pressure-sensitive, heat-activated, and/or water soluble. The adhesive is particularly useful because it can help improve the flow of sample a device. For example, when the device is an immunosensor, the adhesive can help prevent the blood from clotting in chambers of the immunosensor. This results in a more efficient and accurate determination of the concentration of the sample. Methods of making the composition and device in which the composition can be used are provided, as are methods of using the same.

Abstract: In vitro electrochemical sensor that provide accurate and repeatable analysis of a sample of biological fluid are provided. In some embodiments, the sensors have a measurement zone that has a volume less than the volume of the sample chamber. The measurement zone could have a volume of no more than about 0.2 ?L.

Abstract: A method for monitoring a select analyte in a sample in an electrochemical system. The method includes applying to the electrochemical system a time-varying potential superimposed on a DC potential to generate a signal; and discerning from the signal a contribution from the select analyte by resolving an estimation equation based on a Faradaic signal component and a nonfaradaic signal component.

Abstract: A practical measuring device and a measuring method that allow simply measuring average postprandial blood glucose from urinary glucose. The blood glucose measuring device includes a measuring unit that measures postprandial urinary glucose from subject's urine at a predetermined time after meal, a processing unit that calculates average postprandial blood glucose through a period up to the predetermined time after meal, based on the postprandial urinary glucose, a storage unit that stores calibration data including the postprandial urinary glucose and the average postprandial blood glucose in association, and an output unit that outputs data indicating the calculated average postprandial blood glucose. The processing unit calculates the average postprandial blood glucose, based on the postprandial urinary glucose from the urine of the subject who has intaken a desired amount of water or perspired in the period up to the predetermined time after meal, and the calibration data.

Abstract: The present invention is directed to membranes composed liquid crystals having continuous aqueous channels, such as a lyotropic liquid crystal, including a cubic phase lyotropic liquid crystal, and to electrochemical sensors equipped with such membranes. The membranes are useful in limiting the diffusion of an analyte to a working electrode in an electrochemical sensor so that the sensor does not saturate and/or remains linearly responsive over a large range of analyte concentrations. Electrochemical sensors equipped with membranes of the present invention demonstrate considerable sensitivity and stability, and a large signal-to-noise ratio, in a variety of conditions.

Abstract: The present invention relates to devices, systems and methods for measuring cell barrier function. In particular, the present invention relates to microfluidic devices for use in in vitro models of the blood-brain barrier and modeling the transport across this barrier.

Abstract: A sensing device includes a sensing surface, and a matrix overlaying the sensing surface. The sensing device includes a photoformed membrane overlaying at least a portion of the matrix. The photoformed membrane includes a directly photoformed organosiloxane polymer that is substantially permeable to gaseous molecules and substantially impermeable to non-gaseous molecules and ions.

Abstract: A method for operating a measuring meter for an electrochemical test strip is provided. The method comprises steps of applying a voltage to electrodes of the test strip at least during one of a sample presence detection period and an incubation period; and repeatedly increasing and decreasing the voltage during at least one of the sample presence detection period and the incubation period.

Abstract: A system and method employing at least one semiconductor device, or an arrangement of insulating and metal layers, having at least one detecting region which can include, for example, a recess or opening therein, for detecting a charge representative of a component of a polymer, such as a nucleic acid strand, proximate to the detecting region, and a method for manufacturing such a semiconductor device. The system and method can thus be used for sequencing individual nucleotides or bases of ribonucleic acid (RNA) or deoxyribonucleic acid (DNA). The semiconductor device includes at least two doped regions, such as two n-type regions implanted in a p-type semiconductor layer or two p-type regions implanted in an n-type semiconductor layer. The detecting region permits a current to pass between the two doped regions in response to the presence of the component of the polymer, such as a base of a DNA or RNA strand.

Abstract: Embodiments of the invention provide amperometric analyte sensors having optimized elements such as electrodes formed from sputtered platinum compositions as well as layers of material selected to optimize the characteristics of a wide variety of sensor elements and sensors. While embodiments of the innovation can be used in a variety of contexts, typical embodiments of the invention include glucose sensors used in the management of diabetes.

Abstract: The invention relates to a transdermal analyte monitoring system comprising a medium adapted to interface with a biological membrane and to receive an analyte from the biological membrane and an electrode assembly comprising a plurality of electrodes, wherein the medium is adapted to react continuously with the analyte, an electrical signal is detected by the electrode assembly, and the electrical signal correlates to an analyte value. The analyte value may be the flux of the analyte through the biological membrane or the concentration of the analyte in a body fluid of a subject. The medium may comprise a vinyl acetate based hydrogel, an agarose based hydrogel, or a polyethylene glycol diacrylate (PEG-DA) based hydrogel, for example. The surface region of the electrode may comprise pure platinum. The system may include an interference filter located between the biological membrane and the electrode assembly for reducing interference in the system.

Abstract: Measurement of the series track resistance of a working and counter electrode pair in an electrochemical test strip provide error detection for multiple variations in the quality of the test strip, as well as the operation of strip in the test meter. In particular, a single measurement of series resistance can be used to detect and generate an error message when an incorrect reading is likely to result due to (1) damaged electrode tracks, (2) fouled electrode surfaces, (3) dirty strip contacts, or (4) short circuit between the electrodes.

Abstract: A BUN (blood urea nitrogen) sensor containing immobilized carbonic anhydrase and immobilized urease for the in vitro detection of urea nitrogen in blood and biological samples with improved performance and precision characteristics.

Abstract: Embodiments of nanoelectronic sensors are described, including sensors for detecting analytes such ammonia. An environmental control system employing nanoelectronic sensors is described. A personnel safety system configured as a disposable badge employing nanoelectronic sensors is described. A method of dynamic sampling and exposure of a sensor providing a number of operational advantages is described.

Abstract: Electrochemical devices, methods, and systems for detecting and quantifying analytes are disclosed. A chemical detection reagent is locally generated in a test solution by electrochemical reaction of a precursor compound caused to migrate into the test solution from a precursor solution separated from the test solution by a cell separator. This approach provides precise metering of the reagent, via the charge passed, and avoids the need to store a reagent solution that may be chemically unstable. In one embodiment, the starch concentration in a colloidal solution can be measured via spectroscopic detection of a blue complex formed by the interaction of starch with iodine produced, on demand, by electrochemical oxidation of iodide ion. The approach may also be used to characterize certain types of analytes. The invention is amenable to automation and is particularly useful for on-line monitoring of production processes, including the inclusion of feed back loop mechanisms for process control.

Abstract: A biosensor for determining the concentration of an analyte in a biological sample. The biosensor comprises a support, a reference electrode or a counter electrode or both disposed on the support, a working electrode disposed on the support, the working electrode spaced apart from the other electrode or electrodes on the support, a covering layer defining a sample chamber over the electrodes, an aperture in the covering layer for receiving a sample, and at least one layer of mesh in the sample chamber between the covering layer and the electrodes. The at least one layer of mesh has coated thereon a silicone surfactant. Certain silicone surfactants are as effective as fluorinated surfactants with respect to performance of biosensors. These surfactants, when coated onto the mesh layer of the biosensor, are effective in facilitating the transport of aqueous test samples, such as blood, in the sample chamber.

Abstract: A method for determining a concentration of an analyte is disclosed. The method includes applying a potential excitation to a fluid sample containing an analyte and determining if a current decay curve associated with the fluid sample has entered an analyte depletion stage. The method also includes measuring a plurality of current values associated with the fluid sample during the analyte depletion stage and calculating an analyte concentration based on at least one of the plurality of current values.

Abstract: The present invention provides a method of electrochemically measuring a hematocrit (Hct) value using a sensor, capable of achieving excellent measurement accuracy and reliability and also provides a sensor used in the method. The method of electrochemically measuring a hematocrit (Hct) value of blood include: providing an electrode system having a working electrode (11) and a counter electrode (12), in which a redox substance is provided on the counter electrode (12) but not on the working electrode (11); supplying blood to the electrode system; applying a voltage to the electrode system in this state to cause an oxidation current or a reduction current to flow between the working electrode (11) and the counter electrode (12); detecting the oxidation current or the reduction current; and determining a Hct value based on a value of the detected current.

Abstract: A biosensor system determines an analyte concentration of a biological sample using an electrochemical process without Cottrell decay. The biosensor system generates an output signal having a transient decay, where the output signal is not inversely proportional to the square root of the time. The transient decay is greater or less than the ?0.5 decay constant of a Cottrell decay. The transient decay may result from a relatively short incubation period, relatively small sample reservoir volumes, relatively small distances between electrode surfaces and the lid of the sensor strip, and/or relatively short excitations in relation to the average initial thickness of the reagent layer. The biosensor system determines the analyte concentration from the output signal having a transient decay.

Abstract: A biosensor for determining the concentration of an analyte in a biological sample. The biosensor comprises a support, a reference electrode or a counter electrode or both disposed on the support, a working electrode disposed on the support, the working electrode spaced apart from the other electrode or electrodes on the support, a covering layer defining a sample chamber over the electrodes, an aperture in the covering layer for receiving a sample, and at least one layer of mesh in the sample chamber between the covering layer and the electrodes. The at least one layer of mesh has coated thereon a silicone surfactant. Certain silicone surfactants are as effective as fluorinated surfactants with respect to performance of biosensors. These surfactants, when coated onto the mesh layer of the biosensor, are effective in facilitating the transport of aqueous test samples, such as blood, in the sample chamber.

Abstract: An electrochemical sensor is provided that exhibits improved adhesion of the membrane to the nitride layer used as an insulating layer in silicon- or silicon-oxide-based electrochemical sensing devices. The sensing devices include a substrate, an oxide disposed on the substrate, a nitride disposed on the oxide, an electrically conductive structure disposed on the oxide layer, and an electrode disposed on the oxide layer and electrically coupled to the electrically conductive structure. At least one opening is formed in the nitride layer to form at least one adhesion trench that exposes a surface region of an oxide layer underlying the nitride layer. The membrane covers the electrode, and contacts the oxide surface regions exposed by the adhesion trenches. The contact between the membrane and the oxide surface region provides for improved adhesion of the membrane to the electrochemical sensing device.

Abstract: A bioreactor for cultivating living cells in a liquid medium. In one embodiment of the present invention, the bioreactor has a first substrate having a first surface and an opposite second surface, defining a chamber therebetween for receiving the cells and the liquid medium. The bioreactor further has a barrier dividing the chamber into a first subchamber and a second subchamber, wherein the barrier has a porosity to allow the first subchamber and the second subchamber in fluid communication and allow at least one predetermined type of cells to permeate between the first subchamber and the second subchamber.

Abstract: The present disclosure relates to an improved enzyme sensor comprising a cover membrane layer of a porous polymeric material, the outer surface and pore mouths of at least one face of the porous polymeric material being covered by a hydrophilic polymer. The sensor is useful determining the presence or amount of biological analytes, e.g., glucose, lactate, creatine, creatinine, etc.

Abstract: A method of assessing toxicity of a candidate agent to a sample of cells comprises the steps of providing a sample of cells, exposing the cells to the candidate agent for a suitable period of time, assaying the cells to measure data for at least one parameter of cellular function; and correlating the measured data of the at least one parameter of cellular function with toxicity, wherein the step of exposing the cells to the candidate agent is carried out in the presence of a reagent capable of facilitating transport of the candidate agent into the cell. The transport reagent may be an endocytosis, pinocytosis inducing agent, a peptide, or a liposome. The at least one parameter of cellular function may be selected from the group consisting of: cell viability; proliferation rate; membrane integrity; and a metabolic parameter.

Abstract: The present invention provides a method of measuring a component in blood, by which the amounts of blood cells and an interfering substance can be measured with high accuracy and high reliability and the amount of the component can be corrected accurately based on the amounts of the blood cells and the interfering substance. In a sensor for measuring a blood component, a first working electrode 13 measures a current that flows during a redox reaction of a blood component, a second working electrode 17 measures the amount of blood cells, and a third working electrode 12 measures the amount of an interfering substance. Next, based on the measurement results, the amount of the blood component to be measured is corrected. Thus, more accurate and precise measurement of the amount of the blood component can be realized.

Abstract: A mesoporous silica structure having a plurality of mesopores includes a dendritic framework having mesopores. 90% or more of the mesopores observable in a 500 nm×500 nm area pass through the framework in a direction perpendicular to a longitudinal direction of the framework.

Abstract: The present invention deals with a device for quick estimation of biochemical oxygen demand of beverage waste water. This device consists of an immobilized microbial membrane attached to an electrode, multimeter and a laptop workstation installed with a developed software. BOD measurement of beverage waste water using this device is rapid, reproducible and effective as compared to conventional titration based methods. This device also excludes COD estimation as required for BOD estimation of waste water. This bio-electrochemical device may find wide commercial application in beverage industries emanating waste waters.

Abstract: Electrochemical biosensors, methods of making biosensors and methods of detecting a target analyte in a sample to be analyzed are provided. A preferred embodiment device comprises a non-conductive polymer deposited on the electrode to form a matrix material having a plurality of pores; a capture biomolecule immobilized on the electrode such that the binding of the target analyte to the capture biomolecule effectively blocks a sufficient number of pores in the matrix material to produce a measurable decrease in the rate of a redox reaction occurring at the electrode; a current source for driving a redox reaction at the electrode; a redox species in contact with the electrode; and a detector element operatively connected to the electrode to detect the measureable decrease of a change in the rate of a redox reaction occurring due to the blockage of pores in the matrix material by the target analyte.

Abstract: A nanopore device includes a membrane having a nanopore extending there through forming a channel from a first side of the membrane to a second side of the membrane. The surface of the channel and first side of the membrane are modified with a hydrophobic coating. A first lipid monolayer is deposited on the first side of the membrane, and a second lipid monolayer is deposited on the second side of the membrane, wherein the hydrophobic coating causes spontaneous generation of a lipid bilayer across the nanopore orifice. Sensing entities, such as a protein ion channel, can be inserted and removed from the bilayer by adjusting transmembrane pressure, and adapter molecules can be electrostatically trapped in the ion channel by applying high transmembrane voltages, while resistance or current flow through the sensing entity can be measured electrically.

Abstract: Disclosed are nanometer to micron scale functionalized apertures constructed on a substrate made of glass, carbon, semiconductors or polymeric materials that allow for the real time detection of biological materials or chemical moieties. Many apertures can exist on one substrate allowing for the simultaneous detection of numerous chemical and biological molecules. One embodiment features a macrocyclic ring attached to cross-linkers, wherein the macrocyclic ring has a biological or chemical probe extending through the aperture. Another embodiment achieves functionalization by attaching chemical or biological anchors directly to the walls of the apertures via cross-linkers.

Abstract: Measurement of the series track resistance of a working and counter electrode pair in an electrochemical test strip provide error detection for multiple variations in the quality of the test strip, as well as the operation of strip in the test meter. In particular, a single measurement of series resistance can be used to detect and generate an error message when an incorrect reading is likely to result due to (1) damaged electrode tracks, (2) fouled electrode surfaces, (3) dirty strip contacts, or (4) short circuit between the electrodes.

Abstract: The present invention provides biosensor test devices for measuring the presence or amount of an analyte in a biological fluid. The devices have a base plate that has an electrode system embedded therein, and a hydrophilic porous material situated on the base plate. A hydrophobic protective layer is situated on the hydrophilic porous material, and a cover is placed on the hydrophobic protective layer to complete the device. Some embodiments also use an insulating layer, which can be situated between the base layer and the hydrophilic porous material. The cover of the device has an opening present therein, situated over the electrodes, so that the electrodes communicate with the exterior of the device through the groove. The insulating layer can also have a groove situated therein, which in one embodiment is placed to align with the groove in the cover. The invention also provides methods of manufacturing the devices, and methods of using them.

Abstract: A high throughput biological screening assay comprising at least two anodes, at least two cathodes acting as the reference electrode, and a polymer membrane placed between each anode and cathode, wherein the at least two anodes comprise a biological culture, and wherein the at least two cathodes comprise an oxidizing agent and a buffering agent. The high throughput biological screening assay wherein the at least two cathodes are connected in parallel to simulate the connection between the same cathode and different anodes. The high throughput biological screening assay further including an external resistor or open circuit and means for measuring the voltage across the external resistor or open circuit. A method of measuring power generation using a single cathode as a reference electrode to monitor the biological production of energy. A method of correlating bacterial biofilm formation within an operational microbial fuel cell directly to current output.

Abstract: An electrochemical test sensor adapted to assist in determining the concentration of analyte in a fluid sample is disclosed. The sensor comprises a base that assists in forming an opening for introducing the fluid sample, a working electrode being coupled to the base, and a counter electrode being coupled to the base, the counter electrode and the working electrode being adapted to be in electrical communication with a detector of electrical current, and a sub-element being coupled to the base. A major portion of the counter electrode is located downstream relative to the opening and at least a portion of the working electrode. The sub-element is located upstream relative to the working electrode such that when electrical communication occurs between only the sub-element and the working electrode there is insufficient flow of electrical current through the detector to determine the concentration of the analyte in the fluid sample.