Peptide-capped functionalized Ag/Au bimetal nanoclusters with enhanced red fluorescence for lysosome-targeted imaging of hypochlorite in living cells.

Bioimaging probes for monitoring intracellular reactive oxygen species have important implications for cell biology research. Herein, we developed peptide-capped silver/gold nanoclusters (peptide@Ag/Au NCs) for lysosome-targeted imaging of hypochlorite (ClO-). The peptide@Ag/Au NCs were synthesized via a one-pot method using peptide as both a template and a reducing agent. The fluorescence intensity and absolute quantum yield of peptide@Ag/Au NCs were much higher than those of peptide-capped gold nanoclusters and silver nanoclusters. In the presence of ClO-, the fluorescence of peptide@Ag/Au NCs was quenched, accompanied by a redshift due to ClO--induced oxidation of the peptide ligand and decreased Ag content in Ag/Au NCs. The relative fluorescence intensity F0/F had favourable linearity for ClO- concentrations in the range 0.1-100 μmol/L (R2 = 0.9954), with a detection limit (LOD) of 80 nmol/L. The lysosome-targeted peptide@Ag/Au NCs were applied to detect ClO- in lysosomes in living cells via fluorescence imaging.