Photothermal Efficiencies of Nanoshells and Nanorods for Clinical Therapeutic Applications

With clinical trials for photothermal tumor ablation using laser-excited tunable plasmonic nanoparticles already underway, increasing understanding of the efficacy of plasmonic nanoparticle-based photothermal heating takes on increased urgency. Here we report a comparative study of the photothermal transduction efficiency of SiO2/Au nanoshells, Au2S/Au nanoshells, and Au nanorods, directly relevant to applications that rely on the photothermal response of plasmonic nanoparticles. We compare the experimental photothermal transduction efficiencies with the theoretical absorption efficiencies for each nanoparticle type. Our analysis assumes a distribution of randomly oriented nanorods, as would occur naturally in the tumor vasculature. In our study, photothermal transduction efficiencies differed by a factor of 3 or less between the different types of nanoparticle studied. Both experiment and theory show that particle size plays a dominant role in determining transduction efficiency, with larger particles more efficient for both absorption and scattering, enabling simultaneous photothermal heating and bioimaging contrast enhancement.