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AssigneeImmunivest Corporation
InventorsPaul A. Liberti, Galla C. Rao, Joseph N. Chiarappa
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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.
In a process for making resuspendable, coated magnetic particles by direct application of a coating material to a particulate magnetic substrate, wherein said substrate is prepared from a particulate, magnetic, transition metal oxide starting material selected from the group consisting of chromium (IV) oxide (CrO.sub.2), cobalt ferrite (CoFe.sub.2 O.sub.4), copper ferrite (CuFe.sub.2 O.sub.4), dysprosium ferrogarnet (DyFe.sub.5 O.sub.12), dysprosium orthoferrite (DyFeO.sub.3), erbium orthoferrite (ErFeO.sub.3), gadolinium ferrogarnet (Fe.sub.5 Gd.sub.3 O.sub.12), holmium iron garnet (Fe.sub.5 Ho.sub.3 O.sub.12), iron nickel manganese oxide (FeMnNiO.sub.4), .gamma.-iron oxide (maghemite), iron oxide (magnetite), .alpha.-iron oxide (hematite), lanthanum ferrite (FeLaO.sub.3), magnesium ferrite (MgFe.sub.2 O.sub.4), manganese ferrite (Fe.sub.2 MnO.sub.4), manganese dioxide (MnO.sub.2), neodymium dititanate (Nd.sub.2 O.sub.7 Ti.sub.2), aluminum nickel ferrite (Al.sub.0.2 Fe.sub.1.8 NiO.sub.4), nickel-zinc ferrite (Fe.sub.2 Ni.sub.0.5 O.sub.4 Zn.sub.0.5), nickel zinc ferrite (Fe.sub.2 Ni.sub.0.4 Zn.sub.0.6), nickel zinc ferrite (Fe.sub.2 Ni.sub.0.8 O.sub.4 Zn.sub.0.2), nickel (II) oxide (NiO), nickel ferrite (Fe.sub.2 NiO.sub.4), samarium ferrogarnet (Fe.sub.5 O.sub.12 Sm.sub.3), silver lanthan ferrite (Ag.sub.0.5 Fe.sub.12 La.sub.0.5 O.sub.19), yttrium iron garnet (Fe.sub.5 O.sub.12 Y.sub.3), yttrium orthoferrite (FeO.sub.3 Y), said starting material being subdivided to yield a plurality of aggregable, smaller sized particles, suspended in a liquid medium and contacted with said coating material to form a mixture, before substantial aggregation of said particles occurs, the improvement which comprises heating the mixture to a temperature of at least about 45.degree. C. for a time sufficient for said coating material to adhere to said substrate.
A process for making a stable suspension of resuspendable magnetic particles, said process comprising:
A resuspendable coated magnetic, transition metal oxide particle exhibiting colloidal stability in a 1 molar salt solution, as indicated by an increase in particle size of no greater than two-fold upon exposure of said particle to said salt solution for a period of up to 24 hours at room temperature.
Dependencies are inferred from the claim text.