Ratiometric fluorescence aptasensor for the detection of patulin in apple juice based on the octahedral UiO-66-TCPP metal-organic framework and aptamer systems.

Patulin (PAT) is a potentially harmful mycotoxin to human health and is known to contaminate apple juice. In this work, we developed a ratiometric fluorescence aptasensor using tetrakis(4-carboxyphenyl)porphyrin (HTCPP)-treated octahedral UiO-66-NH (defined as UiO-66-TCPP) to detect PAT. This 2-aminoterephthalic acid and HTCPP functionalized metal-organic framework showed multiple adsorption effects (hydrogen bonding and π-π stacking) on the aptamer (Apt) and served as a quenching material. When the target PAT bound specifically to the Apt, the fluorescence of the 6-carboxyfluorescein-labeled Apt would recover, and the fluorescence of the HTCPP ligand remained unchanged. This ratiometric fluorescence property improved the accuracy of PAT detection. Moreover, the introduction of the HTCPP ligand enhanced the quenching efficiency of UiO-66-NH, thus improving the sensitivity of the fluorescent aptasensor (UiO-66-TCPP vs. UiO-66-NH: 0.0162 ng/mL vs. 1.8 ng/mL). In addition, we used UiO-66-TCPP to detect PAT in apple juice samples. This work provides a good paradigm for the construction of ratiometric fluorescence aptasensors with high sensitivity and accuracy.