Introduction of cisplatin into polymeric micelle

Cisplatin, an anticancer drug, was bound to aspartic acid residues of poly(ethylene glycol)-poly(aspartic acid) block copolymer (PEG-P(Asp)) by ligand substitution reaction at platinum atoms of cisplatin. At a molar ratio of cisplatin and the aspartic acid residue of 1:1, polymeric micelles were formed with an average diameter of 16 nm. A polymeric micelle fraction was easily purified by ultrafiltration, and a micellar structure of this fraction was stable in distilled water and NaCl solution at 37 degrees C for 24 h. The polymeric micelle showed 1/8 to 1/5 cytotoxicity of intact cisplatin against murine B 16 melanoma cells during 24-72 h incubation. This suggests release of platinum complexes from the micelle.