Patent ID: 7226617

Claim:
A method of preparing a thermosensitive and biodegradable microgel wherein a) the microgel has a chemically cross-linked network comprising at least one negative temperature-sensitive macromolecule and one biodegradable group represented by structural formula: wherein represents chemical cross-linked bonds; F(DC) 2 represents a polymeric chain between the cross-linked bonds; F is a temperature-sensitive block copolymer of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO); D is a biodegradable moiety; and C is a cross-linked moiety b) the microgel is in the form of microparticles prepared by the following steps: i) co-polymerizing a biocompatible polymer or oligomer F with an internal ester D by ring opening polymerization of D in the presence of F using a catalyst; wherein F is a temperature-sensitive polymer or oligomer; D is a biodegradable moiety; ii) end capping the copolymer with a crosslinkable moiety C to provide a macromer with crosslinkable ends; iii) cross linking the crosslinkable end(s) of the macromer to form the microparticles of the microgel by inverse suspension polymerization, wherein the continuous phase is a water-insoluble organic solvent and the dispersion phase consists of a hydrophilic medium in which the macromer is present, c. the microgel is useful for encapsulating a drug post polymerization; and d. the drug encapsulated microgel is injectable into the body.