Patent ID: 7695905

Claim:
Magnetic fine particles having a lower critical solution temperature, and having immobilized thereto at least one substance selected from the group consisting of biotin and avidin, wherein the at least one substance selected from biotin and avidin is immobilized to the magnetic fine particles through a polymer having a lower critical solution temperature which comprises at least one member selected from the group consisting of poly-N-substituted acrylamide derivatives and their copolymers, poly-N-substituted methacrylamide and copolymers thereof, polyvinyl methyl ether, polypropylene oxide, polyethylene oxide, poly-N-vinylalkylamide, and poly-N-isopropylacrylamide, and wherein the polymer further comprises a unit derived from a comonomer containing at least one substance selected from the group consisting of biotin and avidin.