Abstract: The invention relates to an improved method for the manufacture of magnetically responsive particles, also called ferrofluids. The improved method involves a heat treatment step, which may occur at various times during the preparation of the materials, including during subdivision of the magnetic starting material, during the addion of a coating material, after formation of a magnetically responsive particle, or some combination thereof. The materials formed by such a process have numerous advantages over materials formed by other processes, including enhanced salt stability, increased coating uptake, and increased binding capacity. These ferrofluids have applications in a variety of preparative and diagnostic techniques, including immunoassay, cell separations, toxicity testing, food testing, environmental analysis, and MRI.

Abstract: A method of qualitative analysis of microscopic biological specimens is disclosed in which the specimens are rendered magnetically responsive by immunosspecific binding with feuromagnetic colloid. The specimens are placed in a vessel having a feuromagnetic capture structure supported on a transparent wall. The vessel is then placed in a magnetic field for inducing a high gradient region in the vicinity of the capture structure and, in particular, adjacent to the capture structure along the direction of the applied field. The magnetically responsive specimens are collected and immobilized by the high gradient along the wall adjacent to the capture structure for unobstructed microscopic observation. Subpapulations of distinct types of cells can thus be observed and differentiated. As transport force, such as gravity or an externally applied magnetic gradient, may be applied to the vessel to move the specimens into the high gradient region.

Abstract: Microbiological entities, such as cells or microbes, are immobilized in a single-file linear array for optical analysis. Colloidal magnetic particles having a binding agent, such as ligand for attachment with a corresponding receptor, are bound to the entities suspended in a fluid medium. The fluid medium is placed into a vessel having a ferromagnetic capture structure including an elongated linear collection surface with a diameter less than that of the microbiological species of interest. The vessel is placed into a magnetic field for inducing a magnetic gradient in a region along the collection surface of the ferromagnetic capture structure. The magnetically-labeled entities are attracted toward the collection surface and immobilized thereon in a linear array. Microscopic optical and fluorescence observations, and sequential chemical reactions and mechanical manipulations may be performed on the line of immobilized entities.

Abstract: A method of quantitative analysis of microscopic biological specimens in a fluid medium is disclosed in which the specimens are rendered magnetically responsive by immunospecific binding with ferromagnetic colloid. A known quantity of magnetically-responsive marker particles are added to the fluid medium. The fluid medium is then subjected to a magnetic separation process, to collect the magnetic species from the fluid. The collected species are resuspended in a second fluid medium, and the relative quantities thereof are enumerated to determine the concentration of the desired biological specimen in the first fluid medium. The marker particles may comprise magnetic particles having a relatively large magnetic moment, a magnetic moment approximately equal to the magnetically-labelled biological speciment of interest, or both in order to compensate the determination for variations in immunospecific binding affinity and/or magnetic collection efficiency.

Abstract: The present invention relates to apparatus and methods for separating, immobilizing, and quantifying biological substances from within a fluid medium. Biological substances are observed by employing a high internal gradient magnetic capture structure formed within a vessel, in conjunction with an externally-applied force for transporting magnetically responsive material toward the capture structure. The invention is also useful in conducting quantitative analysis and sample preparation in conjunction with automated cell enumeration techniques.

Abstract: Biological entities such as cells, microbes, or components thereof are labeled with a magnetic colloid containing microscopic magnetic particles. The magnetic particles have a coating capable of biospecific or non-specific binding with the entities. An immobilization apparatus includes a non-magnetic vessel having a ferromagnetic collection structure for attracting the entities toward a collection surface upon which the magnetically labeled entities are immobilized subsequent to placement of the vessel on a support between two magnets. The ferromagnetic collection structure preferably has a sharp edge or high curvature for intensifying the magnetic field and for collecting the entities in a monolayer. The vessel includes an un-obstructed observation path so that immobilized entities may be observed and/or manipulated. The ferromagnetic collection structure may be arranged in various two dimensional patterns to provide a desired collection configuration.

Abstract: A magnetic separation apparatus is disclosed herein. The apparatus includes a flow-through vessel defining a plenum and an inlet port for introducing fluid into the plenum. A hydrodynamic damping structure is provided between the inlet port and plenum for reducing turbulence in the fluid. A mounting device is provided with a slot therein for supporting and receiving the vessel. The mounting device also supports a first array of magnets along one side of the slot and arranged adjacent one another to face the slot with alternating polarity, and a second array of magnets along the opposite side of the slot from the first array arranged adjacent one another to face the slot with alternating polarity and confronting and magnetically opposing the magnets in the first array.

Abstract: A method and apparatus for determining qualitatively or quantitatively the presence of analyte bound to a separation media without doing a bound/free separation. In the method, the bound fraction is collected in an assay region of a body of liquid which includes the free analyte, and the assay is performed by comparing the radiant-energy response in the assay region to the radiant-energy response in a control region of the body of liquid which is free of bound analyte. The apparatus has a chamber which contains the body of liquid, one or more collection elements and a control element and position in the body of liquid parallel to an opaque wall which has a colliminating slit in registry with each element. Each slit enables sensing of the radiant-energy response from the body of liquid between the slit and its associated elements.

Abstract: The invention relates to an improved method for the manufacture of magnetically responsive particles, also called ferrofluids. The improved method involves a heat treatment step, which may occur at various times during the preparation of the materials, including during subdivision of the magnetic starting material, during the addion of a coating material, after formation of a magnetically responsive particle, or some combination thereof. The materials formed by such a process have numerous advantages over materials formed by other processes, including enhanced salt stability, increased coating uptake, and increased binding capacity. These ferrofluids have applications in a variety of preparative and diagnostic techniques, including immunoassay, cell separations, toxicity testing, food testing, environmental analysis, and MRI.

Abstract: A method for determining the presence and/or concentration of a target substance e.g. protein, nucleic acid, bioparticle etc. in a fluid sample is provided. The method disclosed combines elements of immunoassays, coated cup assays and magnetic particle separation to effect the quantitation and recovery of an analyte in solution. Also the method ensures the non-reorientation of magnetically collected material by linking the magnetic particles to a collection surface via a specific binding pair. This linkage immobilizes the magnetic-analyte-containing material and thus allows for vigorous washing and reagent addition without significant redistribution or displacement. Thus the assay of this invention offers the speed of diffusion controlled kinetics as in a ferrofluid assay, the speed of collection of labeled target substance as in a magnetic assay as well as the ability to magnetically monolayer the ferrofluid, all of which is combined with the ease of washing and signal detection found in a coated cup assay.

Abstract: A method for separation of a mixture of biological entities into at least three distinct, subpopulations. Different antibodies are provided, with each antibody bound to a solid support in a unique manner such that by a manipulation of the physical or chemical environment, the bonds between the antibodies and the solid supports can be selectively broken. The mixed population of cells is incubated with the antibodies. The cells are magnetically separated from a test medium and collected in a monolayer upon a collection surface. Then by manipulation of the physicochemical environment, specific linkages can be broken and desired cell subpopulations released from the collection surface. This method has medically significant diagnostic and therapeutic applications, as entire cell types can be separated from non-malignant medically vital cell types. Cancer can be diagnosed, staged, and monitored. Genetic analysis from maternal blood, CVS, or amniocentesis samples is possible.

Abstract: Methods and devices are disclosed which are useful for collecting magnetic materials in either internally or externally generated magnetic gradient fields, followed by resuspension into solution with a simple manipulation of the magnetic device. The methods provide for removal of excess reagent, washing of magnetic material, and resuspension for analysis, among other uses. The methods are applicable to all types of biological material that are susceptible to magnetic labelling, including, for example, cells, viruses, proteins, hormones, and receptor-ligand complexes. Several devices are disclosed to take advantage of the method for cellular and immunoassay applications, including both internal and external devices. Both flow-through and static separators are disclosed.

Abstract: Stable suspensions of coated magnetic particles, preferably resuspendable bioactive particles particularly useful in Magnetic Resonance Imaging, are produced by disrupting, what are presumed to be, crystalline agglomerates of a parent particulate magnetic starting material in the presence of a coating material, such that coating can take place during the disruption. The particles are generally coated in suspension yielding a stable suspension of subdivided particles. With the proper selection of a coating material, preferably a protein or other biochemically or biologically active polymer such as an antibody, a resuspendable (colloidal) bioactive product is obtained.

Abstract: Methods and devices are provided for separation of magnetic particles and/or magnetic-associated substances from non-magnetic associated substances and media. The methods are specifically applicable to biological separation, and utilize a phase phenomenon arising from mutual interactions between suspended magnetic particles and interactions with the suspension medium. The phenomenon is exploited to produce and maintain a distinct, structured phase of magnetic particles, or ferrophase, within a multi-phase liquid system. A ferrophase is established within a separation chamber prior to introducing therein a test sample containing the target substances to be separated. The formation of a ferrophase is used to transport target substances from regions of relatively low magnetic field gradient to regions of relatively high magnetic field gradient within a high-gradient magnetic separation apparatus.

Abstract: A method is provided for direct coating of transiently stable, colloidal particulate magnetic substrates with various synthetic or naturally-occurring polymers, particularly biologically-active peptides and proteins. The resulting coated resuspendable, colloidal magnetic particles are particularly adapted for use in bioanalytical procedures involving affinity separation, or the like. There is also provided a method for selectively binding chemically-treated colloidal magnetic particles to polyelectrolytes, e.g., to facilitate extraction of nucleic acids from cell lysates.

Abstract: A magnetic separator for isolating magnetically-labeled substances of interest, such as immunological agents, from a non-magnetic test medium using a method of high gradient magnetic separation. The target substance is contacted with microscopic magnetic particles having a receptor for binding with the target substance. The test medium containing the magnetic particles is held in a non-magnetic container and placed into a gap within an arrangement of magnets for causing the magnetic particles to adhere to selected locations upon the interior wall of the container. The quantity of magnetic particles may be controlled to cause the magnetic particles collected upon the interior wall to form a monolayer. The magnets are arranged upon a yoke which may provide linear, surrounding multipolar, or partially surrounding multipolar configurations of magnetic pole faces about the gap.