A fluorescence-colorimetric dual-mode strategy for smartphone sensing of tetracycline antibiotics

Tetracycline antibiotics (TCs), widely used as broad-spectrum bacteriostatic agents in veterinary and medical applications, had cause serious harm to human beings, and thus, on-site and portable quantification methods for TCs evaluation are urgently necessary. In this study, through integrating inner filter effect (IFE) into antenna effects, a response approach with fluorescence and colorimetric dual signals was constructed for portable sensing of TCs based on metal-organic framework (MOF)-based nanoprobe, i.e., NH₂-MIL-101(Fe)-Eu³⁺. With this strategy, TCs first quenches the blue fluorescence of nanoprobe by IFE and subsequently excites sharp red fluorescence of Eu³⁺ through antenna effect, achieving the bimodal response in one fluorescence spectrum. Notably, the complexation of TCs and nanoprobe promotes electron transfer between Fe(Ⅲ) and Fe(Ⅱ), enhancing the peroxidase-like activity of the nanoprobe for specific colorimetric evaluation of TCs with assistance of 3,3′,5,5′-tetramethylbenzidine (TMB) indicator. The ratiometric fluorescence-colorimetric dual-mode sensing strategy demonstrates an ultra-high sensitivity with low limits of detection (LODs) of 8.74 × 10⁻⁵ ppm, and provides reliable recoveries from 89.74 % to 108.25 % in the honey samples. Additionally, a rapid “two-solution” extraction strategy proposed in this study, as demonstrated by statistical comparisons (Two one-sided tests (TOST), Deming regression, and Bland-Altman analysis), yields result comparable to laboratory extraction methods across various food and environmental samples, adapting to different matrices to minimize preparation steps and time. Expectedly, this simple and responsive dual-mode sensing approach, which can be combined with smartphone recognition due to the chromaticity changes of MOF probe, provides a new direction for advancing on-site detection of contaminants in food and environmental samples.