In this study, we demonstrate that the uptake rate of the surface-modified gold nanoparticles (GNPs) with folic acid by specific cells can be increased significantly, if the membranes of these cells have sufficient folic-acid receptors. Two human breast cancer cell lines were studied; one is MDA-MB-435S cell, and the other T-47D cell. The expression of the folic acid receptors of the former is much higher than that of the latter. These cells were incubated with media containing bare GNPs or GNPs conjugated with folic acid individually. Due to the unique optical behavior (i.e. surface plasmon resonance) of GNPs, the uptake amount of GNPs by cells can be identified by using the laser scanning confocal microscopy. Our experiments show that the uptake amount of GNPs in MDAMB-435S cells is higher than that in T-47D cells for the same culture time, if the culture medium contains bare GNPs. Moreover, if the GNPs conjugated with folic acid are used for the culture, the uptake rate of GNPs by MDA-MB-435S cells is improved more. In contrast, the uptake rates of both GNPs are almost the same by T-47D cells. The phenomenon indicates that the uptake rate of GNPs can be improved via the ligand-receptor endocytosis, compared with the nonspecific endocytosis. Therefore, the uptake rate of GNPs conjugated with folic acid by MDA-MB-435S cells is higher than that of bare GNPs.

Combining the scattered light of gold nanoparticles (GNPs) and the fluorescence of dye molecules, a compound cellular imaging of laser scanning confocal microscopy (LSCM) is obtained. The human breast cancer cell line (MDA-MB-435S, BCRC 60429) is used for experiment. These cells are incubated with a glucose medium containing GNPs for 26 hours, and then are stained by Prodium Iodide (PI) for their nuclei. By using a single laser to illuminate these cells and adjusting the ranges of two bandpass filters for the detection, the scattered light from the GNPs and the fluorescence of PI can be induced simultaneously, but be detected separately without crosstalk. Furthermore, a compound cellular image can be obtained by merging the two images of the expressions of GNP and PI together. From the TEM images of these cells, it is observed that GNPs are aggregated in the vesicles of the cytoplasm due to the cell’s endocytosis. The aggregation of GNPs makes the surface plasmon resonance band of GNPs broadened, so that strong scattered light from GNPs can be generated by the illumination of different-wavelength lasers (458, 488, 514, 561, and 633 nm).

Photothermal effects of laser-activated surface plasmonic gold nanoparticles on the apoptosis and osteogenesis of osteoblast-like cells Lih-Rou Rau,1 Wan-Yu Huang,1 Jiunn-Woei Liaw,2–5 Shiao-Wen Tsai1,3,6 1Graduate Institute of Biochemical and Biomedical Engineering, 2Department of Mechanical Engineering, 3Center for Biomedical Engineering, Chang Gung University, 4Institute for Radiological Research, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan, 5Center for Advanced Molecular Imaging and Translation, 6Department of Orthopaedic Surgery, Chang Gung Memorial Hospital, Linkou, Taiwan, Republic of China 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

This study investigates the radiobiological effects of gold nanoparticles (GNPs) as radiosensitizers for proton beam therapy (PBT). Specifically, we explore the enhanced production of reactive oxygen species (ROS) in GNP-loaded tumor cells irradiated by a 230 MeV proton beam in a spread-out Bragg peak (SOBP) zone obtained by a passive scattering system. Our findings indicate that the radiosensitization enhancement factor is 1.24 at 30% cell survival fraction, 8 days after 6 Gy proton beam irradiation. Since protons deposit the majority of their energy at the SOBP region and interact with GNPs to induce more ejected electrons from the high-Z GNPs, these ejected electrons then react with water molecules to produce excessive ROS that can damage cellular organelles. Laser scanning confocal microscopy reveals the excessive ROS induced inside the GNP-loaded cells immediately after proton irradiation. Furthermore, the damage to cytoskeletons and mitochondrial dysfunction in GNP-loaded cells caused by the induced ROS becomes significantly severe, 48 h after proton irradiation. Our biological evidence suggests that the cytotoxicity of GNP-enhanced ROS production has the potential to increase the tumoricidal efficacy of PBT.

The dispersion relations of surface plasmon wave (SPW) propagating along a convex or concave metal-dielectric interface with a radius of curvature are studied by solving the root of a characteristic equation in terms of Bessel and Hankel functions of complex order numerically. For the convex geometry, a metallic circular cylinder embedded in a dielectric host is modeled, whereas for the concave one, a dielectric cylinder in a metallic host is modeled. We found that the phase velocity of SPW along a convex interface is always less than that of SPW along a planar one. On the contrary, the phase velocity of a concave case is faster than that of a planar one. For both cases, the attenuation constants are larger than a planar one, due to the radial radiation of the energy into the surrounding medium, except the dissipation in the metal.