Light-sensitive liposomes containing coumarin-proteinoid conjugate.

Photo-sensitive liposomes were prepared by modifying the surface with coumarin derivative-proteinoid conjugate. Epoxypropoxy coumarin (EPC) was conjugated to proteinoid composed of Asp, Ser and Leu (PASL) using the reaction mixture of which EPC/PASL ratio was 8/1 (w/w). The molar ratio of Asp residue/Ser residue/Leu residue/EPC residue of the resulting conjugate was calculated to be 71.1:18.6/6.3/4.0 on 1H NMR spectrum. Egg phosphatidylcholine (egg PC) liposomes bearing PASL-EPC conjugate was prepared by hydrating egg PC dry film with a buffer solution containing the conjugate. Egg PC/PASL-EPC conjugate ratios (w/w) in the preparation were 100:1 to 100:20, and the specific loadings of EPC residue in the liposomes were 0.0002 mg/mg to 0.0018 mg/mg. The release from the liposomes prepared using the egg PC/PASL-EPC conjugate ratios of 100:5 began to markedly increase 30 min after the irradiation of lambda = 254 nm and the release degree in 180 min was about 30%. Without the UV irradiation, no appreciable release was observed.