A ratiometric fluorescent probe consisting of Zn-MOF and calcium ion for sensitive and visual detection of doxycycline

Abstract

Background

The global consumption of antibiotics is steadily rising, with doxycycline being extensively utilized in both animal husbandry and the treatment of COVID-19. Overuse of this antibiotic may result in residual accumulation and pose potential health risks. Conventional detection methods are often complex and labor-intensive, whereas fluorescence analysis offers advantages such as high sensitivity and rapid response. In this work, the development of a simple and efficient MOF-based fluorescent sensor for the detection of doxycycline holds considerable promise for practical applications.

Results

In this paper, a unique 3D metal-organic framework Zn[C₁₈H₁₆O₄N₄]·C₂H₆SO·2H₂O (Zn-MOF) for rapid detection of doxycycline was successfully synthesized and analyzed by SEM, PXRD, FTIR, TGA and UV-vis. The fluorescence of Zn-MOF at 430 nm is quenched by the static quenching and inner filter effect between Zn-MOF and doxycycline with detection limit of 2.01 μM. Concurrently, Ca²⁺ can combine with doxycycline and form the Zn-MOF that generates a new fluorescence signal at 550 nm. By mixing the Zn-MOF and Ca²⁺, a ratiometric fluorescent probe can be created. The ratio of fluorescence intensity (F₅₅₀/F₄₃₀) to doxycycline concentration revealed a good linear relationship and detection limit of 1.25 μM. The fluorescence detection efficiency of the ratiometric fluorescent probe is almost twice that of the single metal-organic framework.

Significance

The ratiometric fluorescent probe also exhibited excellent selectivity and stability in both ionic and antibiotic solution. As with the concentration of doxycycline increase, the color of the probe and Ca²⁺ shifted from blue to yellow, allowing for visual detection of doxycycline and facilitating its application in rapid detection in real life.