Reduced graphene oxide nanosheets decorated with AuPd bimetallic nanoparticles: a multifunctional material for photothermal therapy of cancer cells

Gold nanoparticles (Au NPs) and reduced graphene oxide (rGO) mediated hyperthermia are the two most widely explored systems used for the photothermal ablation of cancer cells. We show that the photothermal conversion and efficiency of these nanomaterials can be improved not only by combining them into one material, but also by forming bimetallic AuPd embedded on rGO. The AuPd NPs–rGO nanocomposites were prepared by a simple one-step chemical reduction technique using the individual metallic salts, graphene oxide (GO) and ascorbic acid as a green reducing agent. The AuPd NPs–rGO nanocomposites were covalently functionalized with poly(ethylene glycol) (PEG) chains and characterized by high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and UV/Vis spectrophotometry. Covalent attachment of PEG units to the AuPd NPs–rGO nanocomposites greatly improved the solubility and stability of the nanocomposites in biological media and ensured its biocompatibility towards cancer cells such as HeLa cells. The near-infrared photothermal properties of AuPd NPs–rGO–PEG nanocomposites were evaluated using a continuous laser at 800 nm with power densities between 0.5 and 2 W cm−2. The nanocomposite was successfully used for the in vitro photothermal ablation of HeLa cells. At 1 W cm−2, the total killing of HeLa cells was achieved through irradiation of AuPd NPs–rGO–PEG nanocomposites incubated cells for 10 min at a particle concentration of 20 μg mL−1. Such high efficiency was principally assigned to the synergetic effects of rGO and AuPd NPs.