Development of gold/gold sulfide nanoparticles for photothermal and photodynamic therapy

Cancer is a high-mortality disease. There is an urgent need for alternative or adjuvant therapies with high specificity and efficacy. Light-based therapies offer an excellent locality and turn on/off modality to the treatment. In photothermal therapy, the nanoparticle is irradiated with a light source (LED or laser) at a specific wavelength, which is absorbed by the nanoparticle and converted into heat, causing damage to the surrounding tissue. In Photodynamic therapy (PDT), the irradiated photosensitizer, which is usually an organic molecule, generates reactive oxygen species (ROS) which cause apoptosis, DNA damage, and cell death. PDT is used in the clinic for specific cancer types, such as head-and-neck cancer. Nanoparticles are very attractive for various applications due to their tunable physical, chemical, and biological features. Gold nanoparticles are one of the most studied due to their inert and biocompatible nature and are used in different fields such as catalysis, energy, and medicine as a theranostic agent. In this thesis, a new type of colloidally stable gold nanoparticle with near-infrared absorbance, namely gold-gold sulfide (GGS) nanoparticles were developed. Then, these GGS nanoparticles were developed into a multifunctional nanoparticle (NP) to offer combination phototherapy; PTT and PDT for enhanced therapeutic outcome. In vitro toxicity studies of these nanoparticles and the efficacy of PTT/PDT therapy combinations of prostate cancer cell lines have been discussed.