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

Abstract

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/cm² and 80 mW/cm² 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.

Keywords:

• pulsed laser
• photothermal
• gold nanoparticles
• osteoblast
• apoptosis
• mineralization

Supplementary materials

Figure S1 TEM image of AuNPs (A) and UV–vis adsorption spectrum of AuNPs (B).

Abbreviations: TEM, transmission electron microscopic; AuNP, gold nanoparticle; UV–vis, ultraviolet–visible; OD, optical density.

Figure S2 Confocal microscopy photograph of cells treated with H₂O₂.

Notes: (A) Annexin V-Alexa Fluor 488 was used to indicate PS, shown in green; DAPI was used to stain nuclei, shown in blue; (B)Texas Red-X phalloidin was used to label cytoskeletal F-actin, shown in red; and (C) superimposition of (A) and (B).

Abbreviations: PS, phosphatidylserine; DAPI, 4′,6-diamidino-2-phenylindole.

Figure S3 Dark-field image of cells after treated with AuNPs and laser irradiation of 100 mW/cm².

Abbreviation: AuNP, gold nanoparticle.

Acknowledgments

The authors are grateful to the Molecular Imaging Center at Chang Gung Memorial Hospital for providing hyperspectral microscopy. This research was supported by the National Science Council, Taiwan, Republic of China. (NSC 103-2221- E-182-012) and by Chang Gung Memorial Hospital (CMR-PD2A0052, CMRPD2A0053, and CIRPD2E0031).

Disclosure

The authors report no conflicts of interest in this work.