Patent ID: 7683041

Claim:
A method of delivering to a cellular compartment in an interior of a cell of an organism a bioactive material that stimulates an immune response in the cell in the organism, comprising: introducing to the cell a microgel composition, the microgel composition comprising: (a) a polymer having a bisacryloyl acetal crosslinker said bisacryloyl acetal crosslinker being essentially non-hydrolyzable above pH 7, but hydrolyzable below pH 6, wherein said bisacryloyl acetal crosslinker has the formula R 2 CH(OR 1 ) 2 , wherein R 1 is an acryloyl group; and R 2 is Ar-X where (i) X is a water solubilizing group selected from hydrogen, methoxy, —O—(CH 2 —CH 2 —O) n —CH 3 wherein n is from 1 to 10, —), —O—CH 2 —CH 2 —O—C(O)—O—Ph—NO 2 and O—CH 2 —CH 2 —CH 2 —NH—CO- (dextran polysaccharide), wherein the dextran polysaccharide having a molecular weight from 300 to 100,000 daltons; and (ii) Ar is an aryl group and wherein said crosslinker hydrolyzes at pH 4.5 to pH 7.4; wherein said polymer has a particle size between 0.1-10 microns and cross linkages between 1 and 20 mole percent, and (b) the bioactive material, wherein said bioactive material is selected from peptides, proteins, DNA, RNA, antibodies, and interleukins; effecting hydrolysis of the polymer within the cellular compartment of the cell, wherein the compartment is acidic, and cleaving said crosslinker, thereby releasing said bioactive material into the interior of the cell.