Laser immunotherapy with gold nanorods causes selective killing of tumour cells

Therapeutic approaches that exploit nanoparticles to deliver drugs selectively to cancer cells are currently considered one of the most promising avenues in the area of cancer therapeutics. Recently, gold nanorods (AuNRs) have shown promising biological applications due to their unique electronic and optical properties. In this paper, we have demonstrated the anti-cancer potential of gold nanorods with low power laser light. Gold nanorods (AuNRs), surface modified with poly (styrene sulfonate) PSS and functionalized with epidermal growth factor receptor antibody conjugated with gold nanorods (anti-EGFR-AuNRs) were successfully synthesised and characterized by UV-Visible-NIR spectrophotometry and High Resolution Transmission Electron Microscopy (HR-TEM). Inductively Coupled Plasmon Atomic Emission Spectrometry (ICP-AES) and Immunofluorescence studies confirmed the efficient uptake of these functionalized gold nanorods by human squamous carcinoma cells, A431. The in vitro photothermal therapy was conducted in four groups - control, laser alone, unconjugated AuNRs with laser and anti-EGFR conjugated AuNRs with laser. Phase contrast images have revealed cell morphology changes and cell death after the laser irradiation. In order to determine whether the cell death occur due to apoptosis or necrosis, we have evaluated the biochemical parameters such as lactate dehydrogenase release, reactive oxygen species level, mitochondrial membrane potential and caspase-3 activity. Flow cytometry analysis have shown the cell cycle changes after laser irradiation with antibody conjugated gold nanorods. Thus the results of our experiments confirmed that immunolabeled gold nanorods can selectively destruct the cancer cells and induce its apoptosis through ROS mediated mitochondrial pathway under low power laser exposure.