pH-Responsive Au(<scp>i</scp>)-disulfide nanoparticles with tunable aggregation-induced emission for monitoring intragastric acidity

Aggregation-induced emission (AIE)-featuring Au(i) complexes are superior probes for physiological environment monitoring in living organisms owing to their excellent biocompatibility and efficient luminescent properties. However, the intrinsic obstacle of poor water stability and lack of response to biological stimuli greatly restrict their practical application in biological systems. Herein, water-stable and pH-responsive Au(i)-disulfide nanoparticles (NPs) with AIE characteristics were designed. The NPs were prepared by integrating a pH-responsive moiety, cysteine (Cys), into Au(i)-thiolate (SR) complexes, and the Au(i)-SR-Cys structure was formed through disulfide bonds. Hydrophilic Cys was located on the outer layer of the NPs, endowing the spherical NPs with high stability and remarkable monodispersity in water. In addition, Cys endowed the NPs with pH-responsive characteristics. These unique advantages enable them to hold great promise as luminescent probes to monitor intragastric acidity in an acid suppression therapy. To the best of our knowledge, this work is the first example of luminescent Au(i) materials to monitor physiological changes.