Thermo-responsive hydrogel-coated gold nanoshells

This manuscript describes the structural and optical properties of a new hybrid nanoparticle comprised of a gold shell/silica core structure (similar to 120 nm in diameter) coated with an implantable hydrogel polymer overlayer (similar to 20 nm in thickness). These nanoparticles are being developed as thermally modulated drug-delivery vehicles that respond to ambient changes in temperature. A unique feature of these materials is that the thermally sensitive hydrogel coatings can be modulated by exposure to light via excitation of the strong plasmon resonance of the gold shell/silica core particles. The gold nanoshell particles were tailored to absorb near-infrared light, which can pass readily through tissue and bone. The thermo-responsive hydrogel coating was prepared via radical polymerization of a selected mixture of N-isoproprylacrylamide and acrylic acid. The structure and morphology of the composite nanoparticles were examined by FE-SEM and TEM. UV-vis spectroscopy was used to characterize their optical properties, and DLS was used to determine their average hydrodynamic diameter as a function of temperature. As a whole, the results conclusively demonstrate that these composite nanoparticles can be reproducibly prepared, and their responses to changes in temperature are completely consistent with their use as nanoscale drug-delivery vehicles.