PH-Responsive Au(i)-disulfide nanoparticles with tunable aggregation-induced emission for monitoring intragastric acidity.

Jianxing Wang,Lei Su,Jie Li,Zhijun Zhang,Dong Wang,Xueji Zhang,Ben Zhong Tang,Ying Li,Lei Wang

doi:10.1039/d0sc01843k

Abstract

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.

Highlights

The Aggregation-induced emission (AIE) characteristics enable Au(I) materials to overcome the difficulties of the aggregation-caused quenching (ACQ) effect, making them serving as superior probes to monitor physiological changes in biological systems, by virtue of their excellent sensitivity, large Stokes shi, high signal-to noise ratio and high photostability.[18,19,20,21,22]
The Au 4f spectrum of the NCs could be deconvoluted into Au(0) and Au(I) components with binding energies (BEs) of 83.7 eV and 84.4 eV corresponding to the inner Au(0) core and the outer Au(I) shell, respectively, and the Au(I) content in all the Au atoms was determined to be 75% (Fig. S2A†)
The luminescence of Au(I) NPs could be attributed to the slower radiative relaxation via the triplet-centered states through ligand-to-metal charge transfer (LMCT) or ligand-to-metal-metal charge transfer (LMMCT)

Summary

Introduction

As a family of luminescent probes with excellent biocompatibility, gold-based luminescent materials have been widely applied in biological systems,[12,13,14] Of particular interest are aggregation-induced emission (AIE)-featuring Au(I) complexes.[15,16,17] The AIE characteristics enable Au(I) materials to overcome the difficulties of the ACQ effect, making them serving as superior probes to monitor physiological changes in biological systems, by virtue of their excellent sensitivity, large Stokes shi , high signal-to noise ratio and high photostability.[18,19,20,21,22] scarcely any of AIE-featuring Au(I) complexes are applied in living systems, since most of them showed poor stability in water, large size, and a strong tendency to precipitate from water, making them difficult to survive in physiological environments.[15,23,24] only a handful of AIE-featuring Au(I) complexes exhibited speci c responses to biological environments resulting from the lack of well-6472 | Chem. Owing to the pH-responsive AIE characteristics, the Au(I)-disul de complex-based nanoparticles (NPs) can serve as a prominent luminescent probe to determine intragastric acidity during acid suppression therapy.

Results

Conclusion