GSH-mediated photoactivity of pheophorbide a-conjugated heparin/gold nanoparticle for photodynamic therapy.

In this study, we developed a new photosensitizer (PS)-conjugated hybrid nanoparticle comprised of gold nanoparticle (AuNP) as an efficient energy quencher, polysaccharide heparin and a second generation PS, pheophorbide a (PhA) for PDT. The hybrid nanoparticles (PhA-H/AuNPs) with an average size of 40nm were prepared by surface coating of AuNPs with PhA conjugated heparins via gold-thiol interaction. The glutathione (GSH)-mediated switchable photoactivity of the PhA-H/AuNPs was observed by fluorescence quenching and dequenching behaviors in the absence and presence of GSH. The photoactivity was significantly suppressed in aqueous media, but instantaneously restored at the GSH-rich intracellular environment to generate a strong fluorescence signal together with active production of singlet oxygen species with light treatment. In vitro cell tests revealed marked phototoxicity and high intracellular uptake of PhA-H/AuNPs in contrast with free PhA. The PhA-H/AuNPs also exhibited a prolonged circulation characteristic, enhanced tumor specificity, and improved photodynamic therapeutic efficacy compared with free PhA in tumor-bearing mice. As a result, the PhA-H/AuNPs may serve as an effective smart nanomedicine platform for PDT and have great potential for the clinical treatment of various tumors.