(624c) Environmentally Responsive Gold Nanorod-Polypeptide Assemblies

Environmentally responsive nanoassemblies based on polypeptides and nanoparticles are promising in a number of biological/biomedical applications. We demonstrate the formation of gold nanorod (GNR)-elastin-like polypeptide (ELP) nanoassemblies whose optical response can be remotely controlled based on near-infrared (NIR) light exposure. In this study, cysteine-containing ELPs (C2ELP) were self ?assembled on gold nanorods (GNRs) leading to GNR- C2ELP nanoassemblies. Exposure of GNR- C2ELP assemblies to NIR laser resulted in the heating of GNRs due to surface plasmon resonance. Heat transfer from the GNRs resulted in a temperature increase of the self-assembled C2ELP above its transition temperature (Tt), leading to a detectable phase transition and aggregation of the GNR- C2ELP assemblies. This phase transition was quantified using an optical readout, based on an increase in the optical density of the GNR- C2ELP dispersion. This optical response was seen only in the case of GNR- C2ELP nanoassemblies. While a photothermal response was observed in the case of a dispersion consisting of GNRs alone, no optical response could be seen due to the absence of the C2ELP. In addition C2ELP solutions demonstrated neither a photothermal nor an optical response. The reproducibility and reversibility of optical response of GNR- C2ELP nanoassemblies was demonstrated across multiple cycles following exposure and removal of the laser irradiation. In summary, our results indicate that polypeptides can be interfaced with GNRs resulting in optically responsive nanoassemblies. Current work involves an investigation into the optical and photothermal properties of nanoassemblies using higher cysteine-containing ELP homologues. We anticipate that these nanoassemblies can be useful for sensing, tissue engineering, and drug delivery applications.