ABSTRACT:

We developed nanosized, reduced graphene oxide (nano-rGO) sheets with high near-infrared (NIR) light absorbance and biocompatibility for potential photothermal therapy. The single-layered nano-rGO sheets were ∼20 nm in average lateral dimension, functionalized noncovalently by amphiphilic PEGylated polymer chains to render stability in biological solutions and exhibited 6-fold higher NIR absorption than nonreduced, covalently PEGylated nano-GO. Attaching a targeting peptide bearing the Arg-Gly-Asp (RGD) motif to nano-rGO afforded selective cellular uptake in U87MG cancer cells and highly effective photoablation of cells in vitro. In the absence of any NIR irradiation, nano-rGO exhibited little toxicity in vitro at concentrations well above the doses needed for photothermal heating. This work established nano-rGO as a novel photothermal agent due to its small size, high photothermal efficiency, and low cost as compared to other NIR photothermal agents including gold nanomaterials and carbon nanotubes.

INTRODUCTION:

Photothermal therapy employs photosensitizing agents taken up by cells to generate heat from light absorption, leading to photoablation of the cancer cells and subsequent cell death. To avoid nonspecific heating of healthy cells, photosensitizers must show high absorption in the near-infrared (NIR) and selective uptake in cancerous cells in tumors over normal cells in healthy tissues. Deep penetration and little nonspecific photothermal heating in the NIR window are due to the transparency and low absorption of light by tissues in this optical window. Materials currently under investigation with high optical absorbance in the NIR region for photothermal therapy include gold nanoshells, gold nanorods, gold pyramids, single-walled carbon nanotubes (SWNTs), and multiwalled carbon nanotubes.