Dual-emissive polymeric nanoparticles-Ag nanoclusters hybrid for selective Ratiometric sensing of glutathione via Cu(II) displacement approach.

Ratiometric fluorescence sensing offers improved analytical accuracy through intrinsic calibration, making it a powerful tool for quantitative bioanalysis. In this study, a novel dual-emissive ratiometric fluorescence nanocomposites (NCPs) was created by electrostatically assembling two components: positively charged polyethylenimine-based and pyridoxal-5-phosphate (PLP) functionalized polymeric fluorescent nanoparticles (PEIGPLP NPs; λex = 420 nm, λem = 530 nm) as the responsive signal and negatively charged dihydrolipoic acid (DHLA) stabilized red-emitting silver nanoclusters (DHLA-AgNCs; 420 nm, λem = 667 nm) as the reference signal. In this NCPs (λex = 420 nm, λem = 508, 682 nm), the red emitting fluorescence from the DHLA-AgNCs at 682 nm remains unchanged, whereas the yellow fluorescence of the PEIGPLP NPs peak at 508 nm is selectively quenched by Cu(II) ions due to the CHEQ mechanism. Subsequent addition of GSH selectively restored the fluorescence. The Cu(II) coordinated NCPs (NCPs-Cu(II)) system exhibited a linear fluorescence response to GSH concentrations ranging from 2.49 × 10-6 M to 3.15 × 10-5 M, with a detection limit of 4.42 × 10-6 M. The NCPs-Cu(II) nanoassembly was successfully applied for GSH quantification in real biological fluids such as serum, saliva, and urine. Moreover, the nanocomposite was embedded in a polymeric film, demonstrating its potential for point-of-care diagnostics and on-site environmental monitoring.