Mannose-engineered Eu-MOF for ratiometric fluorescent/colorimetric dual-detection and inhibition of E. coli

Reliable detection and fast inhibition of Escherichia coli (E. coli) are critical for public health and food safety, so the detection-inhibition-integrated strategies become critical. Herein, a mannose-engineered 3,5-dicarboxyphenylboronic acid/curcumin dual-ligand Eu-metal-organic framework (Eu-MOF) was designed as dcMOF@man. Mannose realized the specific identification to E. coli; Eu-MOF exhibited dual-emission at 350 and 633 nm for robust ratiometric fluorescence sensing to E. coli as boronic acid-surface glycan interaction enhanced the emission at 350 nm, while mannose-FimH-mediated interaction attenuates the Eu³⁺ emission at 633 nm. The intensity ratio of I₆₃₃/I₃₅₀ exhibits a good linear relationship to E. coli at the concentration range of 10-10⁷ CFU/mL with a low detection limit of 5 CFU/mL. Concurrently, the dcMOF@man exhibited peroxidase-like activity, enabling E. coli-dependent colorimetric detection based on tetramethylbenzidine oxidation, with the linear range of 10-10⁷ CFU/mL and detection limit of 9 CFU/mL, which was also quantified via smartphone-based RGB analysis for on-site detection. The intrinsic antibacterial activity of curcumin afforded the effective inhibition of E. coli. Moreover, curcumin-mediated antibacterial activity synergizes with mannose targeting, resulting in nearly 100% antibacterial efficiency. Thus, dcMOF@man integrates targeting identification, ratiometric fluorescence sensing, colorimetric detection, and antibacterial functionality within single composite, as a generalizable strategy for on-site bacterial detection and inhibition.