Design of Photosensitive Gold Nanoparticles for Biomedical Applications Based on Self-Consistent Optical Response Theory

Gold nanoparticles (Au NPs) have been studied for both photothermal therapy and imaging. Efficient photothermogenic response to near-infrared light is necessary for in vivo applications. In this study, the photosensitive properties of Au NPs were theoretically analyzed by self-consistent treatment of Maxwell’s equation. With the Au concentration held constant, a single Au NP with a diameter of 60 nm had the most efficient photothermogenic properties by 532 nm laser irradiation. Particularly, due to the multiple interactions of mirror images of localized surface plasmons, closely spaced multiple Au NPs exhibited enhanced photothermogenic properties in the longer wavelength region even when the Au NPs were small. A comparison of the theoretical and experimental results suggests that the multiple Au NPs are created by the seeding growth of Au NPs in the PEGylated dendrimer. These results provide the guiding principles for design of Au NPs suitable for photorelated biomedical applications.