Patent ID: 8658214

Claim:
A method for producing polymer microspheres, the method comprising: preparing a solution including at least two polymers or copolymers; preparing an emulsification of the solution; forming solidified microspheres from the emulsification; drying the solidified microspheres; separating the solidified microspheres according to size; pre-treating the separated, solidified microspheres for crosslinking; freezing the pre-treated microspheres; and crosslinking and sterilizing the frozen, pre-treated microspheres by applying radiation; wherein the crosslinking is carried out such that the polymer microspheres produced are substantially free of crosslinking chemicals or other agents used to stabilize polymers or copolymers; wherein preparing solution includes adding a polymer or copolymer having a low molecular weight and a polymer or copolymer having a high molecular weight such that the resulting solution has a mixture of polymers or copolymers of both high and low molecular weights.