Controlled synthesis of Cu-MOF possessing peroxidase-mimetic activity for the colorimetric detection of tetracycline in aqueous solution

In recent years, antibiotic pollution has become a major concern due to their excessive exposure to humans and the environment. However, the existing instrument-dependent and time-consuming conventional detection approaches are not feasible for the real-time detection of antibiotics at the field level. Herein, two Cu-based metal-organic frameworks (Cu-btc) with the same stoichiometry were synthesized under different reaction conditions. The hydrothermal approach resulted in better structural and crystalline properties of Cu-btc (named as Cu-MOF2) than the preparation under normal laboratory conditions (Cu-MOF1). The high peroxidase-like activity of Cu-MOF2 was further utilized to develop a colorimetric assay for the detection of tetracycline in water. The presence of multiple O- and N-functional groups in tetracycline led the formation of tetracycline-Cu2+ complexes. Tetracycline itself did not cause any change in the color of the TMB-H2O2 system, but it could effectively hinder the colorimetric reaction of TMB with H2O2 in the presence of Cu-MOF2. The designed system demonstrated a low detection limit of 0.23 mu M with a limit of quantification of 0.69 mu M. The performance of this colorimetric assay was also examined in the presence of other possible interfering antibiotics. The good biocompatibility of this sensing platform increases its potential for in vitro biosensing applications.