O/N-carbon dots as a fluorescent nanoprobe for sensitive COX-2 inhibitor detection: comprehensive validation and application to pharmacokinetic studies in rats with acute liver injury.

Etoricoxib (ETX), a widely used selective cyclooxygenase-2 (COX-2) inhibitor, currently does not have a direct spectrofluorometric method suitable for regular bioanalytical measurement. This investigation introduces an innovative spectrofluorometric approach for the determination of ETX, based on orange-emitting oxygen/nitrogen-doped carbon dots (O/N-CDs). The approach relies on a turn-off mechanism where ETX causes concentration-dependent fluorescence quenching of O/N-CDs, primarily through the inner filter effect, further supported by dynamic quenching. The assay demonstrated remarkable linearity across the range of 50-1000 ng mL-1, with a limit of detection developed at 15.80 ng mL-1. Spiked plasma yielded recovery values that ranged from 94.52% to 96.01%. Protein precipitation followed by reversed-phase C18 solid-phase extraction was employed to ensure method selectivity. The clinical significance was demonstrated by the successful implementation in rat plasma pharmacokinetic studies, which included both healthy subjects and those with thioacetamide-induced acute liver injury. The method effectively quantified ETX and identified notable pharmacokinetic variations between the groups. Furthermore, the evaluation of greenness through the multi-color assessment tool and analytical green star area validated the method's positive environmental attributes. This fluorescence-based assay offers a practical, sensitive, and environmentally friendly alternative to traditional chromatographic methods for ETX quantification, facilitating routine bioanalysis, and pharmacokinetic studies.