Construction of Zinc-based metal-organic frameworks for visual ratiometric fluorescence detection of tetracycline

Background: Tetracycline (TC) is frequently utilized as additives in animal feed. The misuse can lead to the residue in food and threaten human health. Results: A ratiometric fluorescence method for tetracycline detection is developed based on Zinc-based metal- organic framework (Zn-MOF) materials. A series of Zn-MOFs are synthesized with phthalic acid derivatives as ligand, and their luminescence properties and interaction with tetracycline are investigated. Thereinto, Zn-BDCOH MOF synthesized with 2-hydroxyterephthalic acid (BDC-OH) as ligand exhibits sensitive fluorescence response to tetracycline. The blue fluorescence of Zn-BDC-OH at 434 nm is quenched by tetracycline due to inner filter effect (IFE), and the green fluorescence of TC at 531 nm is enhanced because of coordination with Zn2+. The fluorescence intensity ratio I 531 /I 434 shows a linear relationship with TC concentration in the range of 0.10-40.0 mu M with a limit of detection at 79 nM. The fluorescence colors of Zn-BDC-OH MOF change from blue to cyan to green accompanying with increasing TC concentration, which enables the visual and semi-quantitative detection of tetracycline by naked eyes. Moreover, combined with a smartphone, the RGB value of the fluorescence color can be further identified. The ratio (G/B) of green channel to blue channel shows a linear relationship with the TC concentration in the range of 0.25-25.0 mu M with a limit of detection at 0.2 mu M. Afterwards, Zn-BDC-OH MOF is successfully applied to detect tetracycline in honey, and the results are consistent with those obtained from chromatography. Significance: The established method exhibits great potential for field visualization and rapid detection of tetracycline.