Gold Nanoparticles and Nanoshells Embedded as Core–Shell Architectures in Hybrid Poly(l-Histidine)-Containing Polymers for Photothermal Therapies

Abstract

We present a facile strategy for the synthesis of hybrid nanoparticles containing gold nanoshells (AuNSs) that absorb at near-infrared (NIR). Poly(ethylene oxide)-b-poly(l-histidine), poly(ethylene oxide)-b-poly(l-histidine)-b-poly(l-phenylalanine), and poly(ethylene oxide)-b-poly(l-histidine)-b-poly(γ-benzyl-l-glutamate) hybrid copolypeptides were used for the development of AuNSs. Spherical nanoparticles (NPs) were initially formed by the self-assembly of the amphiphilic hybrid polypeptides in water. The addition of HAuCl4 followed by heating, resulted in the reduction of the Au(III) by poly(l-histidine) (PHis), leading to the formation of AuNSs only at the PHis layer, thus forming a nanoshell within the preformed NPs. The NPs formed are composed of a poly(ethylene oxide) (PEO) shell, a PHis layer containing the nanoshell and a poly(l-phenylalanine) (PPhe) or poly(γ-benzyl-l-glutamate) (PBLG) core. By controlling the AuNS thickness and the core diameter by the molecular characteristics of the polymeric precursors as well as the PHis/Au(III) ratio, the optical properties of the AuNSs can be fine-tuned to absorb at a specific wavelength. Thus, we achieved a shift of the absorption peak corresponding to longitudinal surface plasmon resonance to NIR wavelengths. The size and the morphology of the polymeric NPs containing AuNSs were examined by TEM and Dynamic Light Scattering. Studies on a dilute solution of polymeric nanoparticles containing AuNSs showed that by irradiation with a low power laser at 808 nm, results to significant increase of its temperature. We present an approach for the design and facile synthesis of biocompatible polymeric nanoparticles featuring AuNSs with a peak optical absorption in the NIR that can be fine-tuned. Therefore, our aim is to present a novel and facile approach for the formation of AuNSs to be used for photothermal therapy.