(a) Schematic depiction of AuNP carrier and glutathione-mediated surface monolayer exchange reaction to release the dye. (b) Schematic representation and fluorescence images using glutathione (GSH-OEt) as an external stimulus to trigger release of HSBDP from AuNPs. GSH-OEt concentrations were varied from 0, 5, and 20 mM in panels 1, 2, and 3, respectively (Adapted from ref. 71).