Dual functions of gold nanorods as photothermal agent and autofluorescence enhancer to track cell death during plasmonic photothermal therapy

Gold nanorods have the potential to localize the treatment procedure by hyperthermia and influence the fluorescence. The longitudinal plasmon peak contributes to the photothermal effect by converting light to heat. When these nanorods are PEGylated, it not only makes it biocompatible but also acts as a spacer layer during fluorescence enhancement. When the PEGylated nanorods are internalized inside the cells through endocytosis, the transverse plasmonic peak combined with the enhanced absorption and scattering properties of the nanorods can enhance the autofluorescence emission intensity from the cell. The autofluorescence from the mitochondria inside cells which reflects the respiratory status of the cell was enhanced two times by the presence of nanorods within the cell. At four minutes, the nanorods incubated cells reached the hyperthermic temperature when illuminated continuously with near infrared laser. The cell viability test and autofluorescence intensity curve showed a similar trend indicating the progress of cell death over time. This is the first report to the best of our knowledge to suggest the potential of exploiting the dual capabilities of gold nanorods as photothermal agents and autofluorescence enhancer to track cell death.