A high-throughput fluorescence immunoassay based on conformational locking strategy of MOFs to enhance AIE effect of CuNCs-CS for bisphenol S analysis in food samples

Abstract

Dietary intake is an important exposure pathway of environmental bisphenols including bisphenol S (BPS, a typical emerging organic pollutant). However, available data on the occurrence and risk assessment of BPS in food samples are limited due to the lack of high-throughput analytical methods. Herein, based on H2O2 inducing fluorescence turn-off signals, a sensitive and high-throughput fluorescence enzyme-linked immunosorbent assay (FELISA) was developed for BPS investigation in beverages. In this system, the fluorescence of copper nanoclusters in ZIF-8 (CuNCs-CS@ZIF-8) could be quenched with the presence of H2O2 owing to the strong oxidation, being served as signal amplification in FELISA. Meanwhile, the aggregation-induced emission (AIE) fluorescence enhancement of CuNCs-CS through the conformational locking of ZIF-8 provided an effective strategy to overcome the intrinsic limitations of FELISA including high background, serious fluorescence quenching in the detection of real samples. Thus, the integration of AIE building blocks into porous ZIF-8 showed obvious advantages in enhancing the analytical performance of FELISA. Under optimized conditions, satisfactory results with good accuracy were achieved in this proposed FELISA, which was applied for the systematic investigation of BPS in foods and further health risk assessments. The results after 100 beverages analysis displayed an average detection frequency of 55%, and the detected concentration of BPS ranged from below the limit of quantification (LOQ) to 12.08 ng/mL with a mean value of 1.717 ng/mL. Besides, the estimated daily intake (EDI) of BPS was calculated to be 0.05449–4.483 ng/kg-bw/day, in which milk–tea drinks contributed to the majority of BPS daily intake (mean EDI = 4.483 ng/kg-bw/day). And the hazard quotient (HQ) according to EDI values indicated that BPS exposure in beverages might not make a considerable impact on human health.