A molecularly imprinted nanoreactor based on biomimetic mineralization of bi-enzymes for specific detection of urea and its analogues

Biological enzymes have been frequently used as sensing probes due to their fast catalytic rate and high selectivity. However, the specificities of biological enzymes are not absolute, which greatly limits the applications of biological enzymes in highly selective detection. For instance, it is found that urease cannot discern urea among its analogs such as hydroxyurea, formamide and acetamide. Herein, a bifunctional nanoreactor with outstanding urease activity and peroxidase-like activity is constructed by embedding urease (Ur) and bovine hemoglobin (BHb) in metal-organic frameworks (MOFs) through biomimetic mineralization. Then, hydrogen peroxide can be catalyzed by the nanoreactor to produce hydroxyl radicals, which enable the formation of molecularly imprinted polymer (MIP) on the surface of nanoreactors by self-initiated polymerization under mild conditions. Impressively, the prepared colorimetric sensing platform shows a wide linear range of 0.08–20.00 mM and a low detection limit of 0.02 mM in urea detection. The interference experiment proves that the sensing results of nanoreactors are not affected by the urea analogs and interfering substances in sewage and body fluids basically. Moreover, the nanoreactor exhibits excellent cyclic and long-term stability in the 35 days of stability tests. This strategy can not only greatly enhance the selectivity of enzymes, but also greatly improve the utilization rate and reduce the cost of biological enzymes.