One-step functionalized gold nanorods as intracellular probe with improved SERS performance and reduced cytotoxicity

An intracellular SERS probe based on gold nanorods (GNRs) is successfully presented with improved SERS performance and greatly reduced cytotoxicity. Unlike the previous layer-by-layer methods to reduce the obvious cytotoxicity of GNRs, the CTAB-stabilized GNRs only need to be treated with hydrochloric acid (HCl) without any other steps. The aqueous solution of the resultant nanorods exhibited an aggregation with limited extend but remained stable for more than 6 months with no sediment being found. Interestingly, the aggregation helps to yield an improved surface enhanced Raman scattering (SERS) performance in comparison with those stabilized by CTAB bilayers. More importantly, the resultant gold nanorods achieve high cell viability as more than 95%, a level comparable to that obtained by traditional layer-by-layer coating method. The greatly increased cell viability suggests that the cytotoxicity of CTAB-stabilized GNRs is mainly caused by free or loosely surrounded CTAB rather than those tightly bound on the surfaces of GNRs. Moreover, when such gold nanorods were incorporated into living cells, they exhibited strong SERS signal as well as very low cytotoxicity. The result suggests that HCl-treated gold nanorods are potentially very feasible substrates for use as highly sensitive SERS probes in biosensing and biomedical diagnostics, for which the fabrication protocol is advantageous in its simplicity and reproducibility.