Photothermal therapy using folate conjugated gold nanoparticles enhances the effects of 6 MV X-ray on mouth epidermal carcinoma cells

The aim of this study was to develop an optimized method for preparation of folate conjugated gold nanoparticles (F-AuNPs) and to investigate its cytotoxic effects and cell apoptosis in combination with photothermal therapy (PTT) and radiotherapy (RT) for the treatment of mouth epidermal carcinoma cells KB. For this purpose, cells were treated with synthesized F-AuNPs at different concentrations for 6 h and then irradiated them with laser beam (532 nm, 0.5 W/cm2, 15 min). After photothermal therapy, the cells were exposed to 6 MV X-ray with a single dose of 2 Gy. MTT assay were performed to evaluate the cell survival rate and apoptosis was determined by flow cytometry using an annexin V-fluorescein isothiocyanate/propidium iodide apoptosis detection kit. No significant cell damage or cell apoptosis from the individual treatment of laser light or F-AuNPs was observed, while viability of cells incubated with F-AuNPs and then exposed to the laser was significantly decreased. Additionally, our results demonstrated that F-AuNPs is good radiosensitizers even at a low concentration such as 20 µM when megavoltage X-ray is used. Also, when KB cells were treated with F-AuNPs under both laser and X-ray irradiation, the cell viability substantially decreased more than F-AuNPs-enhanced PTT alone or F-AuNPs-enhanced RT alone. Flow cytometry assay clearly indicated that F-AuNPs-mediated photo-thermo-radio therapy significantly induced apoptosis. These results confirm that F-AuNPs is a promising and research-worthy nanoconjugate in the field of targeted photo-thermo-radiotherapy of cancer.