Drug delivery by phospholipase A 2 degradable liposomes

Abstract

The effect of poly(ethylene glycol)-phospholipid (PE-PEG) lipopolymers on phospholipase A 2 (PLA 2) hydrolysis of liposomes composed of stearoyl-oleoylphosphatidylcholine (SOPC) was investigated. The PLA 2 lag-time, which is inversely related to the enzymatic activity, was determined by fluorescence, and the zeta-potentials of the liposomes were measured as a function of PE-PEG lipopolymer concentration. A significant decrease in the lag-time, and hence an increase in enzymatic activity, was observed with increasing amounts of the negatively charged PE-PEG lipopolymers incorporated into the SOPC liposomes. The enhancement of the PLA 2 enzymatic activity might involve a stronger PLA 2 binding affinity towards the negatively charged and polymer covered PEG liposomes.