On-site visual detection of patulin in fruit juice via FRET ratiometric sensor utilizing portable device integrated with smartphone

Excessive levels of penicillin (PAT) in fruit juice pose significant risks to food safety and human health. In this study, a ratiometric fluorescence sensor with on-site visualization detection capability had been developed for PAT detection based on Förster resonance energy transfer (FRET) in this study. This strategy utilized MIL-101(Cr) with a wide absorption peak as the energy acceptor, while nitrogen/sulfur-doped graphene quantum dots (N,S-GQDs) conjugated with PAT aptamer with stable blue fluorescence serves as the energy donor, triggering the FRET effect and quenching the blue fluorescence. When exposed to PAT, the aptamer preferentially binded to PAT, separating the donor and acceptor, thereby interrupting the FRET effect and recovering the blue fluorescence. Assisted by the red internal reference fluorescence of gold clusters (AuNCs), the fluorescence changes were observed from red to blue with the concentration range of 0.01–300 ng/mL of PAT and a low limit of detection at 3.29 pg/mL. More importantly, a portable detection device integrated with smartphone was designed for on-site visual PAT detection with satisfactory results. This strategy could provide new opportunities for on-site qualitative and quantitative detection of PAT in actual foods.