Facile preparation of near-infrared fluorescent probes for highly sensitive detection of γ-glutamyl transpeptidase and evaluation of inhibitors

Abstract We developed a simple, high-sensitivity fluorescent sensor with robust selectivity for monitoring γ-glutamyl transpeptidase (GGT) levels based on the inner filter effect (IFE). In this sensing platform, biomass quantum dots (BQDs) were prepared through a one-pot, high-output solvent-thermal approach using cauliflower as a raw material. The prepared BQDs exhibited sufficient water solubility and strong near-infrared emissions (678 nm). We employed γ-L-glutamyl-p-nitroanilide to act as a GGT substrate, with BQD fluorescence levels exhibiting sensitive responses to GGT via IFE. This BQD-based sensing approach was then applied to sensitively detect GGT abundance with a detection limit of 0.276 U/L. Notably, the presented fluorescent sensor shown success in monitoring GGT levels in serum samples, imaging GGT in live cells, and evaluating inhibitors of GGT, disclosing inhibition efficiencies as follows: acivicin > 6-diazo-5-oxo-L-norleucine (DON) > 4L-serineborate (Ser borate). The presented IFE-based strategy may open new avenues for the facile and rapid detection of enzymic activity and enzyme inhibitors using near-infrared fluorescent BQDs, avoiding complex fluorophore modifications and interference from biological autofluorescence.