Effective light-triggered contents release from helper lipid-incorporated liposomes co-encapsulating gemcitabine and a water-soluble photosensitizer.

Triggered drug release is a promising strategy for delivering anticancer drugs to cancer cells and tissues. We found that liposomes co-encapsulating calcein (a water-soluble model drug and fluorescence marker) and talaporfin sodium (TPS, a water-soluble photosensitizer) released the drug upon irradiation with a near-infrared (NIR)-laser. The liposomes were composed of phospholipid (DSPC)/helper lipid (DOPE)/cholesterol/PEG-lipid (PEG2000-DSPE) at a molar ratio of 85/10/5/5 and released a large amount of drug (70%<, within 10 min) upon irradiation, but no drug in the absence of NIR-laser irradiation and/or TPS. NIR-laser-triggered drug release was facilitated by the incorporation of DOPE into the liposomes, and the amount of DOPE incorporated affected drug leakage in the absence of NIR-laser-irradiation at 37 °C (body temperature). Drug leakage was tuned by incorporating cholesterol into the liposomes. NIR-laser-triggered drug release from the liposomes was confirmed using the anticancer drug gemcitabine. NIR-laser treatment of liposomes co-encapsulating gemcitabine and TPS provided the maximum cytotoxic effect towards EMT6/P cells. These results suggest that these novel light sensitive liposomes may be useful for drug delivery to cancer cells.