Comparing the photothermal effects of gold nanorods and single-walled carbon nanotubes in cancer models

Laser Immunotherapy (LIT) is an innovative cancer treatment modality that is specifically targeted towards treating late-stage, metastatic cancer. This treatment modality utilizes laser irradiation in combination with active immune system stimulation to induce a systemic anti-tumor immune response against metastatic cancer. Nanoparticles have recently been utilized to support and increase the photothermal effect of the laser irradiation by absorbing the light energy produced from the laser and converting that energy into thermal energy. In the past, single-walled carbon nanotubes (SWNTs) have been the main choice in nanotechnology, however, recent studies have shown that gold nanorods (AuNRs) are a prospective alternative that may produce photothermal effects similar to SWNTs. Due to the precedence of gold biomaterials currently having approval for use in various treatments for humans, AuNRs are regarded to be a safer option than SWNTs. The goal of this study is to precisely compare any differences in photothermal effects between AuNRs and SWNTs. Both types of nanoparticles were irradiated with the same wavelength of near-infrared light to ascertain the photothermal effects in gel phantom tumor models, aqueous solutions, and metastatic cancer cell cultures. We discerned from the results that the AuNRs could be equally or more effective than SWNTs in absorbing the light energy from the laser and converting it into thermal energy. In both solution and gel studies, AuNRs were shown to be more efficient than SWNTs in creating thermal energy, while in cell studies, no definitive differences between AuNRs and SWNTs were observed. The cytotoxicity of both nanoparticles needs further assessment in future studies. Given these results, AuNRs are comparable to SWNTs, even superior in certain aspects. This advances the opportunity to use AuNRs as replacements for SWNTs in LIT treatments. The results from this study will contribute to any subsequent studies in the development of this cancer modality using photothermal therapy enhanced by nanoparticles.