Nano particulate materials are either produced by industrial processing or engineered for specific biomedical applications. In both cases, their contact with the human body may lead to adverse reactions. The use of nanoparticles in cancer treatment has drawn more attention in different scientific fields. This is due to their altered physical, chemical and biological properties from their macrostructures. The downsizing of the materials to the Nano scale size increases their ability to interact with biological size-equivalent macromolecules. Most of the published papers have focused so far on the cytotoxic effects of nanoparticles (NPs). The present in vitro study investigates the effect of silver “Ag" and cobalt core-silver shell “Co/Ag" nanoparticles on the genetic components of the host response as DNA damage and chromosomal aberrations. In vitro study using HEp-2 human laryngeal carcinoma cells was performed in order to determine the most reliable concentrations of either Ag or Co/Ag nano particles required for tumor cytotoxicity. Monochromatic blue light exposure using a LED source of 460 nm and 200 mW was applied at 5 and 72 hours post NPs incubation. Light exposure of 2 to 15 min has been tested in order to exert the most effective therapy. Results showed that AgNPs and Co/AgNPs mediated photothermal therapy (PTT) offers a promising tool for cancer treatment. It provides considerable efficacy when administered by laryngeal cancer cells. However, both types of particles showed considerable genetic side effects on both DNA and chromosomal levels.