Stepwise Lighting Up Gold(I)–Thiolate Complexes from AIE Nanoaggregates to AIEE Nanoprobes with a ZIF-8 Shell for Glucose Biosensing

Aggregation-induced emission (AIE) or aggregation-induced emission enhancement (AIEE) has endowed gold species with responsive fluorescent properties, favoring their potential applications in sensing, imaging, and therapy. However, it remains an interesting challenge to fabricate fluorophores with both AIE and AIEE effects. Herein, we presented highly luminescent Au(I) thiolate nanocomplex-based biosensors with Zn²⁺ induced-AIE and zeolite imidazolate framework (ZIF-8) induced-AIEE effects. The nonemissive monovalent gold-glutathione complexes (Au^I-SGs) were obtained to synthesize the core-shell Zn²⁺/Au^I-SG@ZIF-8 composites with strong luminescence via the coordination-assisted self-assembly strategy. By immobilizing GOx on the surface of Zn²⁺/Au^I-SG@ZIF-8, Zn²⁺/Au^I-SG@ZIF-8/GOx biosensors exhibited effective responsiveness to glucose, showing a "turn-off" detection model. The mechanism study revealed that the robust luminescence of Zn²⁺/Au^I-SG@ZIF-8 to glucose sensing was attributed to the acid-stimulated degradation of the probe facilitated by H⁺ generated from the glucose oxidase (GOx)-catalyzed oxidation process. To achieve noninvasive and intelligent blood glucose detection, the Zn²⁺/Au^I-SG@ZIF-8/GOx-loaded microneedle (MN)-patch fluorescent platform was further developed. The MN-patch-based sensing platform had promising performance for on-needle capture and in situ glucose detection. This study demonstrated a universal and feasible protocol to construct luminescent biosensors for glucose detection and their potential for the development of MN-based analytical devices.