Thermo- and pH-responsive hydrogel-coated gold nanoparticles prepared from rationally designed surface-confined initiators

Gold nanoparticles (*40 nm in diameter) were encapsulated by a hydrogel overlayer generated by the free radical polymerization of N-isopropylacrylamide-co-acrylic acid (NIPAM-co-AA), which was promoted by a specifically designed radical initiator covalently anchored to the surface of the gold core. The size and morphology of the shell/core nanoparticles were characterized by scanning electron microscopy and transmission electron microscopy. In addition, the optical properties of the nanoparticles were characterized by UV–Visible spectroscopy. Separately, the particle size was evaluated as a function of temperature and pH using dynamic light scattering. The shell/core hydrogel nanoparticles undergo reversible volume changes in water at a lower critical solution temperature (LCST) of *34 C as well as at pH values between 3 and 4. The unique composition and properties of these shell/core hydrogel nanoparticles make them attractive for use as nanoscale drug-delivery vehicles.