Assembling Photosensitive Capsules By Phthalocyanines And Polyelectrolytes For Photodynamic Therapy

A photosensitive capsule consisting of aluminum phthalocyanine tetrasulfonate chloride (AIPcS4Cl) and polyelectrolytes was fabricated by assembling of oppositely charged poly(allylamine hydrochloride) (PAH) and AlPcS4Cl onto the preformed capsule composed of poly(styrene sulfonate) (PSS) and PAH. Capsules constructed through the layer-by-layer (LbL) assembly technique onto the templates and subsequent removal of cores, have received much attention for drug delivery and biomedical applications due to their numerous outstanding features including controlled size and thickness, the loading of the cargos in hollow inner space, and the possibility to functionalize the capsule walls. Encapsulation of photo-responsive substances on capsule walls endows capsules new structural and functional characteristics potentially practical applications. The morphology and structure of the resulting photosensitive capsules were examined by scanning electron microscopy (SEM), and atomic force microscopy (AFM). UV-visible absorption spectra and AFM images confirmed the successful deposition of AIPCS4Cl onto as-prepared hollow capsules. The assembled photosensitive capsules were found to remain intact and spherical morphology in the deposition process. The generation of cytotoxic singlet oxygen (1O2) of the photosensitive capsules under visible light irradiation (670±10nm) was evidenced by ESR measurements and the oxidative reaction between the generated 1O2 and a detector. In vitro cellular experiments showed that the photosensitive capsules exhibited a good biocompatibility in the dark and a higher killing efficacy against MCF-7 cancer cells under visible light irradiation as compared with free AIPCS4Cl, which implies that the assembled photosensitive capsules might be potentially applicable in photodynamic therapy.