▎ 摘　　要

In photodynamic therapy (PDT), selection of an ideal photosensitizer and improvement of its photodynamic activities are currently of great interest. In this work, a chlorophyll-a photosensitizer derivative, p-bromophenylhydrazone-methyl pyropheophorbide-a (BPMppa) with a long absorption wavelength (683 nm) and a large molar extinction coefficient (7.03 x 10(4) M-1 cm(-1)), which is considered to be more suitable for the treatment of deep cancer, is loaded onto pristine graphene using a direct graphite exfoliation process via pi-pi stacking in water. The obtained graphene loaded photosensitizer G-BPMppa composite shows significantly improved water-solubility and dispersity in water, PBS and culture medium, and an increased singlet oxygen (O-1(2)) quantum yield (Phi(Delta) = 60.55%) in DMF solution compared to free BPMppa (Phi(Delta) = 29.2%). In addition, cell experiments indicated that the G-BPMppa composite could be taken up by HeLa cells successfully, showing enhanced intracellular uptake behavior. Owing to its enhanced intracellular uptake and higher O-1(2) quantum yield, G-BPMppa showed remarkably improved PDT efficiency (IC50: 1.36 +/- 0.35 mg mL(-1) of equivalent BPMppa) over free BPMppa after irradiation, but low dark toxicity without irradiation. Moreover, cell morphological changes after G-BPMppa PDT further qualitatively demonstrated that G-BPMppa could induce damage and apoptotic cell death efficiently. Furthermore, the photochemical mechanism of the G-BPMppa mediated PDT process was investigated by using specific quenching agents, sodium azide (SA, a singlet oxygen quencher) and D-mannitol (DM, a hydroxyl radical quencher); the results indicated that type I and type II photodynamic reactions could occur simultaneously, yet the type II reaction (the generation of O-1(2)) might play a predominant role in the G-BPMppa induced PDT process.