Gold nanorod stabilized by thiolated chitosan as photothermal absorber for cancer cell treatment

Gold nanorod (GNR) has great potential in the field of cancer therapy because of its photophysical property in converting near-infrared (NIR) laser light into heat. Fabrication of GNRs by seed-mediated growth method with the aid of cetyltrimethylammonium bromide (CTAB) is a popular approach. However, due to high cytotoxicity of CTAB, it is necessary to modify the surface of CTAB-passivated GNRs for cell-related studies. In this study, thiolated chitosan was synthesized and harnessed to replace CTAB originally used to stabilize GNRs. The average size and morphological shape of CTAB-passivated GNRs (66.0 nm) and thiolated chitosan-modified GNRs (CGNRs) (84.9 nm) were determined by dynamic light scattering and transmission electron microscopy. X-ray photoelectron spectroscopy was used to confirm the existence of Au-S binding energy at 162.4 eV. Cytotoxicity study revealed that CGNRs were much biocompatible than CTAB-stabilized GNRs. Our results showed that CGNRs functionalized with folic acid (FA) could be internalized by human colon HT-29 cancer cells via folate-mediated endocytosis. From the viability of CGNR-laden HT-29 cells irradiated with 808-nm NIR laser light, we demonstrated that CGNR is a potential photothermal nano-absorber for the ablation of malignant cells under NIR laser exposure.