Development of sensing method for mercury ions and cell imaging based on highly fluorescent gold nanoclusters

In this study, sodium 2-Mercaptobenzimidazole-5-sulfonate (SMBD) was used as both a protecting ligand and a reducing agent to synthesize highly fluorescent gold nanoclusters (SMBD@AuNCs). When 360 nm was used as the excitation wavelength, the resultant AuNCs exhibited orange-yellow fluorescence with the maximum emission at 630 nm. In addition, it was found that the fluorescent SMBD@AuNCs could been significantly quenched by Hg2+ over other ions. The phenomenon was further used to design a SMBD@AuNCs-based fluorescence sensing method for the detection of Hg2+. Under the optimal conditions, the detection limit of the proposed method for Hg2+ was 0.5 nM, with a good linear range from 4.0 nM to 20.0 mu M (R-2 = 0.999). Then, it could be successfully utilized for determining trace amount of Hg2+ in real water samples. Furthermore, owing to the excellent biocompatibility, the as-prepared fluorescent AuNCs showed a great potential application in bioimaging fields. Cytotoxicity studies showed that the AuNCs exhibited negligible effects in altering cell proliferation or triggering apoptosis. The as-synthesized AuNCs have been successfully applied as a photoluminescent probe for human bladder cancer cellular imaging.