▎ 摘　　要

Graphene oxide nanosheet (NGO) was covalently functionalized with positively charged, branched polyethylenimine (bPEI) via an amide bond, coated with serum proteins by electrostatic interaction. Operating as a newly fashioned, multifunctional nanocarrier, the processed NGO showed promise for use in combined gene therapy, chemotherapy, photothermal therapy, bioimaging and as a biosensor of cancer cells. Our current research is focused on the systematic studies of mechanisms of cancer cellular uptake, subcellular location, cytotoxicity and the cellular exclusion of the NGO-bPEI nanocarriers. It was observed that NGO-bPEI accumulated in the mitochondria and that long-term retention of NGO-bPEI led to a decrease in mitochondrial membrane potential while levels of reactive oxygen species increased. The mitochondrial effects