Fast and facile preparation of PEGylated graphene from graphene oxide by lysosome targeting delivery of photosensitizer to efficiently enhance photodynamic therapy

Abstract

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 π–π 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.