Comparative study of one pot synthesis of PEGylated gold and silver nanoparticles for imaging and radiosensitization of oral cancers

Head and neck squamous cell carcinomas (HNSCCs) pose strong therapeutic challenges especially oral cancers, due to proximity of functionally vital anatomic regions. Radiotherapy is an important and non-invasive treatment arm for oral cancers. The therapeutic effect of nanoparticles depends on size and type of material. In this study, we aim to synthesize one pot PEGylated gold nanoparticles (Au PEG NPs) and silver nanoparticles (Ag PEG NPs) and evaluate their toxicity and radiosensitization effect in oral cancer KB cell line. CT contrast capacity was measured in a phantom model and compared with clinically used imaging agent. PEGylated Au NPs and Ag NPs were synthesized using PEG 600 as the reducing and stabilizing agent. The surface charge of a well dispersed colloid was +20 mV and-18mV for Au PEG NPs and Ag PEG NPs respectively. Electron microscopy showed their near-spherical morphology. The hydrodynamic diameter for both metallic NPs was similar to 50 +/- 5 nm due to PEG layer and water molecules absorption. Raman shift of around 20 cm(-1) was observed when Au PEG NPs and Ag PEG NPs were coated with PEG. 1H NMR spectroscopy showed extended involvement of -OH in synthesis. The nano architecture was imaged using advanced electron microscopy along with crystal structure. The radiosensitization effect on KB cell line was highest at 4 Gy at dosage of 0.36 mu g/ml Au PEG NPs and 0.23 mu g/ml Ag PEG NPs. Confocal imaging of Hoechst-stained nuclei demonstrated apoptosis in a dose-dependent manner. Au PEG NPs exhibit better CT contrast enhancement ability than clinically used contrast agents and Ag PEG NPs. This study reveals the Au PEG NPs show higher radiosensitization effect compared to the Ag PEG NPs in KB cell line, Au PEG performed better than Ag PEG NPs and clinically used contrast agent Omnipaque due to high atomic number. Therefore, the Au PEG NPs could be a potential candidate as an enhanced radiosensitizer and CT imaging agent against oral cancers.