Poly(ethylene glycol) conjugated nano-graphene oxide for photodynamic therapy

A novel methoxy-poly(ethylene glycol) modified nano-graphene oxide (NGO-mPEG) was designed and synthesized as a photosensitizer (PS) carrier for photodynamic therapy of cancer. NGO with a size below 200 nm was prepared using a modified Hummers' method. NGO was observed by AFM to exhibit a structure with single-layer graphene oxide sheets down to a few nanometers in height. Hydrophilic mPEG conjugation of NGO (NGO-mPEG) was found to enhance solubility in cell culture media. No apparent cytotoxicity of the NGO-mPEG was observed towards MCF-7 carcinoma cell line. Zinc phthalocyanine (ZnPc), a photosensitizer for photodynamic therapy, was loaded in the NGO-PEG through pi-pi stacking and hydrophobic interactions, with the drug loading efficiency up to 14 wt%. Hydrophobic ZnPc was internalized in MCF-7 cells, exhibiting a pronounced phototoxicity in the cells under Xe light irradiation. The results indicate a great potential of NGO-mPEG for photodynamic therapy of cancer.