A label-free fluorescent/electrochemical dual-mode zinc complex biosensor for highly selective and sensitive detection of tetracycline.

BACKGROUND

Tetracycline (TC) is widely used in medicine and animal husbandry, but its excessive use has caused serious environmental and health concerns. Prolonged exposure can induce immune suppression, genetic mutations, and antibiotic resistance, emphasizing the need for rapid and reliable TC detection. Fluorescent (FL) and electrochemical (EL) sensing are attractive for rapid analysis, while FL-EL dual-mode strategies enable self-validation and improved accuracy. Nevertheless, achieving highly sensitive TC detection using an intrinsically integrated FL-EL dual-mode material remains rare and technically challenging.

RESULTS

A rationally designed zinc-based metal-organic framework (Zn-MOF) is reported as a label-free dual-mode sensor for TC detection, synthesized through a rapid, room-temperature, one-pot strategy. The framework incorporates a fluorescent ligand and a redox-active naphthalenediimide unit, enabling concurrent fluorescence enhancement and pronounced electrochemical signal attenuation upon TC binding. The sensor achieves an ultralow detection limit of 0.6 nM, together with high selectivity and excellent tolerance toward coexisting interferents. Quantitative determination of TC in lake water, honey, fish feed and pork samples yields satisfactory recoveries, demonstrating the analytical robustness and reliability of the proposed sensing system in complex real-world matrices.

SIGNIFICANCE: This study presents a rare example of an intrinsically integrated, label-free FL-EL dual-mode MOF sensor for antibiotic analysis. The key novelty lies in combining fluorescence and electrochemical signal generation within a single Zn-MOF without auxiliary labels, aptamers, or nanocomposites. Mechanistic elucidation confirms synergistic coordination and noncovalent interactions as the origin of the dual response, offering a sensitive and practical strategy for TC monitoring.