Enhanced fluorescence of gold nanoclusters composed of HAuCl4 and histidine by glutathione: glutathione detection and selective cancer cell imaging.

Glutathione (GSH) can significantly and selectively enhance the fluorescence intensity of Au nanoclusters (NCs) prepared by blending HAuCl4 and histidine in solution. The quantum yield of the Au NCs after adding GSH can reach above 10%. Besides, GSH capping shifts the excitation peak of Au NCs from ultraviolet (386 nm) to visible light (414 nm) and improves the stability of the Au NCs. The cytotoxicities of the Au NCs with and without GSH for normal lung cells (ATII) and cancerous lung cells (A549) are evaluated. The GSH-capped Au NCs have much less cytotoxicity to both normal and cancer cells, as compared to those without GSH. For Au NCs without GSH, less cytotoxicity is observed in cancer cells than in normal cells. In addtion, the Au NCs can selectively detect GSH over cysteine and homocysteine, the two biothiols which commonly exist in cells that can seriously affect GSH detection. Most importantly, Au NCs without GSH can selectively image the cancer cells, especially for the liver cancer cells whose GSH content is much higher than other cell types. This property makes the Au NCs a powerful probe to distinguish cancer cells from normal cells.