Photothermal effects of laser-activated surface plasmonic gold nanoparticles on the apoptosis and osteogenesis of osteoblast-like cells

The specific properties of gold nanoparticles (AuNPs) make them a novel class of photothermal agents that can induce cancer cell damage and even death through the conversion of optical energy to thermal energy. Most relevant studies have focused on increasing the precision of cell targeting, improving the efficacy of energy transfer, and exploring additional functions. Nevertheless, most cells can uptake nanosized particles through nonspecific endocytosis; therefore, before hyperthermia via AuNPs can be applied for clinical use, it is important to understand the adverse optical-thermal effects of AuNPs on nontargeted cells. However, few studies have investigated the thermal effects induced by pulsed laser-activated AuNPs on nearby healthy cells due to nonspecific treatment. The aim of this study is to evaluate the photothermal effects induced by AuNPs plus a pulsed laser on MG63, an osteoblast-like cell line, specifically examining the effects on cell morphology, viability, death program, and differentiation. The cells were treated with media containing 50 nm AuNPs at a concentration of 5 ppm for 1 hour. Cultured cells were then exposed to irradiation at 60 mW/cm(2) and 80 mW/cm(2) by a Nd:YAG laser (532 nm wavelength). We observed that the cytoskeletons of MG63 cells treated with bare AuNPs followed by pulsed laser irradiation were damaged, and these cells had few bubbles on the cell membrane compared with those that were not treated (control) or were treated with AuNPs or the laser alone. There were no significant differences between the AuNPs plus laser treatment group and the other groups in terms of cell viability, death program analysis results, or alkaline phosphatase and calcium accumulation during culture for up to 21 days. However, the calcium deposit areas in the cells treated with AuNPs plus laser were larger than those in other groups during the early culture period.