Ligand Electronic Effect-Tailored Cobalt-Based Metal–Organic Frameworks Enable Accelerated Entropy-Driven Circuit Reactions for Ultrasensitive Fluorescent Detection of Tetracycline Resistance Genes

Entropy-driven circuit reaction (EDCR) has attracted gradual attention in various fields due to its advantage of constant temperature and nonenzymatic signal amplification. However, critical hurdles that prevents its further applications include the sluggish reaction kinetics arising from the bulk liquid-phase reaction medium and signal leakage. In the present study, we synthesized three Co-based metal-organic frameworks (MOFs) (Co[C₆H₆N₄]X) featuring distinct substituents (-X = -CH₃, -CHO, and -NO₂) and investigates the impact of these substituents on DNA hybridization kinetics behavior. The exceptional reversible adsorption capability of Co[C₆H₆N₄]CHO notably enhances site regeneration efficiency by maximizing π-π stacking interactions and effectively mitigates electrostatic repulsion between DNA chains, significantly elevating DNA hybridization rates. Integration of EDCR with Co[C₆H₆N₄]CHO facilitated the development of a rapid, highly sensitive, and specific antibiotic resistance gene detection system. The adsorption regeneration capability of Co[C₆H₆N₄]CHO substantially improved DNA hybridization efficiency at the interface, yielding a 3-fold enhancement compared to bulk aqueous solutions. Utilizing the tetracycline resistance gene <i>tet</i>(M), a globally distributed antibiotic resistance gene, as the model analyte, we established a newly upgraded MOF-ligand electronic effect-modulated EDCR fluorescent biosensor, displaying an outstanding linear concentration range of 5 pM to 10 nM and achieving a remarkable detection limit of 3.2 pM. This study offers valuable insights into enzyme-free nucleic acid amplification systems by manipulating the electronic effects of MOF substituents, which may shed light on the development of MOF-interfaced EDCR biosensors and their applications.