Intelligent hydrogel and smartphone-assisted colorimetric sensor based on Bi-metallic organic frameworks for effective detection of kanamycin and oxytetracycline.

A smartphone-integrated colorimetric sensor is introduced for the rapid and simultaneous detection of kanamycin (KAN) and oxytetracycline (OTC). This sensor relies on the peroxidase-mimicking activity of Fe/Zr Bi-metallic organic frameworks (UIO-66(Fe/Zr)-NH). This Bi-metallic MOF can facilitate the oxidation of a colorless substrate, 3,3',5,5'-tetramethylbenzidine (TMB), by reactive oxygen species (ROS) derived from hydrogen peroxide (HO), resulting in the formation of blue-colored oxidized TMB (ox-TMB). Consequently, Fe/Zr MOF was utilized for the detection of KAN and OTC under optimized conditions. In the presence of KAN and OTC, the interaction between TMB and HO is inhibited, resulting in varying colorimetric responses. The approach accurately measured KAN and OTC, with detection limits as low as 0.44 and 6.86 nM, respectively. To achieve real-time and portable analysis even in harsh conditions, the proposed sensor was integrated with hydrogel-assisted smartphone technology thereby eliminating the need for expensive and cumbersome laboratory-based testing apparatus. Furthermore, the sensor was successfully used for real water sample analysis, with good recovery results. The proposed sensor provides a quick, visual, and highly sensitive approach for the simultaneous and accurate determination of KAN and OTC residues in polluted water, even at trace quantities. This study advances the application of MOF-based nanozymes in environmental monitoring, while also offering extensive opportunities for use in other fields.