Phase Transfer and Polymer Coating Methods toward Improving the Stability of Metallic Nanoparticles for Biological Applications

Abstract

This paper describes a general method to generate noble metal nanoparticles (NPs) with polymer coatings. One of the widely used approaches to stabilize NPs in aqueous solution involves wrapping NPs with amphiphilic polymers. This methodology has been extensively employed for polymer coating of small hydrophobic NPs (diameter of inorganic core < 20 nm), thereby enabling phase transfer of NPs from an organic solvent to aqueous solution. The polymer coating approach is herein extended to NPs originally synthesized in aqueous solution by a two-step method. First, NPs are subjected to aqueous-to-organic phase transfer. The phase transfer protocol is demonstrated for NPs made of different materials (Au and Ag), sizes (up to 100 nm), and shapes (spheres, rods, and flat-triangular prisms). Second, NPs are coated with an amphiphilic polymer. The colloidal stability of a variety of the newly designed NPs is assayed against different media of biological relevance. In preliminary cellular studies, the biocompatibilit...