Synthesis of Stable Near Infrared Responsive Gold Nanoparticles For Plasmonic Photothermal Therapy Applications

Abstract

The term cancer refers to a class of diseases, in which group of cells display uncontrolled growth, invasion and metastasis. These cells divide and produce new cells in an uncontrolled manner that can spread throughout the body and cause damage to essential organs. With more than 10 million new cases every year, cancer has become one of the most devastating diseases worldwide. It is a third leading cause of death in the developed and second in the developing countries. Traditional treatment options which depend on the stage and type of cancer includes surgery, chemotherapy and radiation therapy. Success rate of these treatment modalities remained limited. Severe side-effects are associated with these treatments, which also compromises the life quality of the patients. Advanced technologies are required and on-going research initiatives are not sufficient for the complete understanding and treatment of this disease. Therefore, development of alternate treatment modalities is the need of the day. Hyperthermia is the treatment modality of cancer in which cancerous cells are exposed to higher temperatures (41-47 ºC). Tumours can selectively destroy in this temperature because of their reduced heat tolerance as compared to normal tissues. In photothermal therapy photo absorbing dyes are used. When these dye molecules are exposed to visible radiations, they get excited and produce localized heat which destroys the cancer cells. Human tissues absorb heavily in the visible region and hence reduce the therapeutic efficiency of conventional photothermal therapy (PTT) agents. This limitation can be overcome if PTT agents with strong photo response in tissue transparent NIR region can be realized. Noble metal nanoparticles can be used as PPT agents because of their enhanced absorption cross section in NIR region, which are several orders larger than those offered by conventional photo absorbing dyes. In addition, metal nanostructures have higher photo stability and they do not suffer from photo-bleaching.