High aspect ratio gold nanorods displayed augmented cellular internalization and surface chemistry mediated cytotoxicity

Due to their unique properties, gold nanorods (GNRs) have shown tremendous potential for advancing bio-imaging and sensing applications. As these nanoparticles display size-dependent optical properties, high aspect ratio GNRs are of particular interest for these applications because of their increased scattering contrast. While studies are emerging that demonstrate successful synthesis of high aspect ratio GNRs, their behavior and fate in a physiological environment has yet to be investigated. The goal of this study was to evaluate the rate of cellular internalization and cytotoxicity of long GNRs (aspect ratio 32) in a human keratinocyte cell line. Additionally, the critical role of surface chemistry in extent of cellular interactions and cytotoxicity was evaluated. Through comparison with aspect ratio 3 GNRs, it was identified that high aspect ratio GNRs displayed enhanced cellular internalization. Furthermore, surface functionalization dictated the quantity of GNRs internalized, with tannic acid having a significant increase over polyethylene glycol. However, the augmented intracellular concentration identified with long, tannic acid GNRs resulted in a considerable degree of cytotoxicity, which was not associated with other GNR conditions. Therefore, while the inclusion of high aspect ratio GNRs may increase the capabilities for nano-based applications, there exist some unintentional toxicological consequences that must also be considered.