▎ 摘　　要

Graphene with unique physical and chemical properties has shown various potential applications in biomedicine. In this study, a fast, facile and mass production method was reported to obtain stable and disperse polyethylene glycol (PEG) modified nanographene (NGO-PEG, 20-40 nm) by covalent functionalization with a linear chain PEG. X-ray photoelectron spectroscopy and UV/Vis indicated the successful preparation of NGO-PEG. Atomic force microscopy was used to show the structure and size of GO and NGO-PEG. The branched polyethylenimine (BPEI) modified NGO-PEG (NGO-PEG-BPEI) was strategically designed and prepared as the targeting drug delivery system to achieve higher specificity. The photosensitizer molecule Chlorin e6 (Ce6) was loaded onto NGO-PEG and NGO-PEG-BPEI via p-p stacking and hydrophobic interactions. The obtained NGO-PEG-Ce6 and NGO-PEG-BPEI-Ce6 show excellent photodynamic efficacy compared to free Ce6 because of the significantly enhanced intracellular delivery of Ce6. The NGO-PEG-BPEI-Ce6 offers a remarkably improved photodynamic efficacy. The drug loading capability, cell uptake, intracellular localization and ROS-producing ability were discussed to explain why NGO-PEG-BPEI-Ce6 had a higher photodynamic efficacy than free Ce6 and NGO-PEG-Ce6. Our study highlights a green route to synthesize stable and disperse NGO-PEG, and identifies a role for NGO-PEG-BPEI as a carrier to target lysosomes to improve the efficacy of photodynamic therapy.