Patent ID: 8865221

Claim:
A swellable and degradable, heat-dried microsphere preparation comprising microspheres which comprise polymer chains, said polymer chains consisting of at least one monomer selected from the group consisting of acrylic acid, methacrylic acid, salts of acrylic acid and methacrylic acid, acrylamide, methacrylamide, N-substituted acrylamides, N-substituted methacrylamides, 2-hydroxyethyl acrylate, and 2-hydroxyethyl methacrylate, provided that: if said monomer is acrylamide, methacrylamide, N-substituted acrylamides, 2-hydroxyethyl acrylate, or 2-hydroxyethyl methacrylate, then said monomer is present in combination with at least one other monomer selected from subgroup 1 consisting of: acrylic acid, methacrylic acid, and salts of acrylic acid and methacrylic acid; wherein: (i) said polymer chains are not crosslinked with a crosslinking agent; (ii) said microspheres degrade substantially completely into high molecular weight soluble polymer after a time greater than 20 minutes in vitro when incubated in phosphate-buffered saline solution in a shaker oven set at 37° C. and 20 revolutions per minute; (iii) said microspheres have a degradation rate that is dependent on the heating temperature and time used to treat the microspheres; and (iv) said microspheres are heat-dried at a temperature of at least about 50° C. for at least about 24 h.