Patent ID: 7795041

Claim:
A coloidally stable multi-polymer-coated magnetic nanocluster, comprising: a. a cluster of super paramagnetic core particles comprising a first polymer attached to said super paramagnetic core particles, wherein said first polymer coats said super paramagnetic core particles; wherein said coating of super paramagnetic core particle with said first polymer provides colloidally unstable cluster of super paramagnetic core particles and wherein said first polymer is selected from the group consisting of (i) a copolymer comprising acrylic acid and either or both of styrene sulfonic acid and vinyl sulfonic acid, (ii) a copolymer comprising acrylic acid and either or both of vinylbenzyl trimethyl ammonium chloride and acrylamidopropyl trimethyl ammonium chloride and (iii) a graft copolymer with a backbone of acrylic acid and side chain comprising either of both of polyethylene oxide and polypropylene oxide; and b. a second polymer attached to said cluster of super paramagnetic particles, wherein said second polymer comprises acrylic acid and is a discrete polymer chain from said first polymer and wherein said second polymer coats said cluster of super paramagnetic particles; wherein coating of said nanocluster with said second polymer renders said multi-polymer-coated magnetic nanocluster colloidally stable; and wherein said attachment of said super paramagnetic core particles to said first polymer and said attachment of said cluster of super paramagnetic core particles to said second polymer comprises a strong or weak interaction between said super paramagnetic core and said first polymer and between said cluster of super paramagnetic core particles and said second polymer; and wherein said multi-polymer-coated magnetic nanocluster ranges in size from 20-1000 nm; and wherein said multi-polymer-coated magnetic nanocluster is stable in solutions of high and/or low ionic strength.