Particle shape-dependent, photothermal properties of gold nanostructured colloids in a physiological fluid

Abstract

The optical properties of gold nanoparticles have made possible the development of biomedical therapies such as hyperthermia. Photothermal properties depend on the size and shape of the nanoparticles. Likewise, the coatings and biological environment define the efficiency of light-to-heat conversion. In this work, we studied the influence of shape (spheres, rods and stars), coating (polyethylene-glycol and fluorescein) and the biological environment (pH=7.4-blood plasma; pH=7.2-breast cancer) on photothermal properties. The light-to heat conversion efficiency of star-shaped gold nanoparticles exceeds that of rods and spheres. Behavioral efficiency is inversely proportional to the heat rate, so the energy transferred to the fluid is lower due reduced contact areas, which result in a lower energy transfer, resulting in a lower final temperature. Rod-shaped gold colloid transfers more energy to physiological fluid, resulting in a higher temperature. Polymeric and fluorescein coating contributes to energy concentration. The energy generated by the plasmonic excitation of spheres and star-shaped gold nanostructures is diminished by the physiological environment. Gold nanostructure photodegradation in physiological fluids decreases thermal capacity due to the agglomeration and precipitation of nanoparticles, resulting forces of attraction and repulsion, caused by the physiological medium