Ratiometric fluorescence/colorimetric sensor based on aptamer-regulated dual-functional UiO-66-TCPP for multimodal detection of β-lactoglobulin

The accurate determination of β-Lactoglobulin (β-LG), a major dairy allergen, is essential for susceptible individuals' health. Here, a multimodal β-LG sensor was developed by utilizing the aptamer (Apt) to regulate the metal-organic framework UiO-66-TCPP’ functions. The prepared UiO-66-TCPP had both fluorescence and peroxidase activity. After adsorbing β-LG Apt, the catalytic activity of UiO-66-TCPP was enhanced through increased substrate affinity and electron transfer, while the fluorescence of 6-carboxyfluorescein-labeled Apt was quenched via multiple interactions with the material, and the fluorescence of UiO-66-TCPP itself remained unchanged. After binding to β-LG, Apt desorbed from UiO-66-TCPP surface, thereby restoring Apt fluorescence and lowering UiO-66-TCPP’ catalytic activity. Thus, a colorimetric/ratiometric fluorescence platform for β-LG sensing in dairy products was constructed with low limits of detection (16.19, 47.69 ng/mL). On-site visual detection was further achieved by RGB analysis on a smartphone. This study proposes novel approaches to creating multi-modal platforms for accurate food allergen determination.