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 (~120 nm in diameter) coated with an implantable hydrogel polymer overlayer (~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.