A ratiometric fluorescence nanosensor for glutathione detection based on spatially confined dual-emission of α-lipoic acid-modified gold nanoclusters and silicon nanoparticles.

The development of dual-emission ratiometric fluorescent probes with aggregation-induced emission enhancement (AIEE) overcomes the limitations of gold nanocluster (Au NC)-based probes, particularly their weak intrinsic fluorescence, in real-world applications. These AIEE probes also exhibit superior detection limits and enhanced sensitivity. A novel combination for the reliable fluorometric detection of glutathione (GSH) was proposed, utilizing aggregation-induced emission enhancement (AIEE) facilitated by electrostatic interaction and spatial confinement. The probe consists of a ratiometric combination of negatively charged α-lipoic acid-modified Au NCs (LA@Au NCs) and positively charged silicon nanoparticles (SiNPs). The addition of SiNPs causes aggregation of LA@Au NCs, enhancing the fluorescence of LA@Au NCs through the AIE effect under electrostatic interaction and spatial confinement. The addition of Cu²⁺ quenched the emission of LA@Au NCs as a result of charge transfer. The fluorescence emissions of LA@Au NCs were restored upon the addition of GSH due to the interaction between GSH and Cu²⁺. Simultaneously, the emission signal of SiNPs remains unchanged, serving as an internal reference signal during GSH measurement. It was found that the fluorescence ratio (F₆₈₀/F₄₆₅) is directly proportional to the concentration of GSH in the range of 0.05-100 μM, with a detection limit of 1.7 nM (S/N = 3). The proposed system was applied to detect GSH in real samples, including dietary supplements, human serum, and saliva samples. This work opens new avenues for constructing novel sensors based on AIEE for detecting biomolecules.