Ultrasensitive detection of alogliptin via fluorescence quenching of terbium-doped carbon quantum dots: mechanistic investigation, Box–Behnken optimization and analytical evaluation

Abstract

A rapid, sensitive, and eco-friendly fluorescence-based analytical method was developed for the determination of the antidiabetic drug alogliptin using terbium-doped carbon quantum dots (Tb-CQDs) as a fluorescence probe. The Tb-CQDs were comprehensively characterized using dynamic light scattering, transmission electron microscopy, UV-vis spectroscopy, and fluorescence spectroscopy, revealing uniform spherical nanoparticles with strong blue emission at 448 nm. The sensing mechanism, investigated through Stern–Volmer analysis and thermodynamic studies, demonstrated a static quenching process involving the formation of a ground state complex between Tb-CQDs and alogliptin, with negative ΔH and positive ΔS values confirming the spontaneous interaction driven by hydrogen bonding and van der Waals forces. To maximize analytical performance, critical parameters affecting the quenching process (pH, Tb-CQDs volume, and incubation time) were systematically optimized using a Box–Behnken design of experiments. The statistical analysis through ANOVA confirmed the significance of the obtained quadratic model (p < 0.0001), revealing that pH and Tb-CQDs volume significantly influenced quenching efficiency both independently and synergistically. Under optimal conditions (pH 8.8, 1.34 mL Tb-CQDs, 1.2 min incubation), the developed method exhibited excellent linearity in the range of 0.01–1.5 μg mL⁻¹ with a limit of detection as low as 3.20 ng mL⁻¹. The validated method was successfully applied for alogliptin analysis in pharmaceutical formulations, spiked human plasma, and environmental water samples, with satisfactory recovery rates (95.10–103.79%). Additionally, the greenness and blueness assessments revealed the superior environmental compatibility and comparable analytical practicality of the Tb-CQDs fluorescence technique compared to conventional HPLC-UV approaches, highlighting the sustainability advantages of this nanomaterial-based sensing platform.