Enzyme-functionalized structural color hydrogel particles for urea detection and elimination

Excessive urea causes poor stress resistance in plants as well as severe environmental issues. In this work, novel structural color hydrogel particles that can degrade and detect urea simultaneously were developed. Inverse opal hydrogel particles (IOHPs) with abundant carboxyl groups and immobilized urease were used. The particles could hydrolyze urea in a solution to determine the concentration of urea. Moreover, because the detection and elimination relied on specific enzyme catalysis and the pH responsiveness of the sensors, the particles displayed high specificity and sensitivity. When the proper ratio of crosslinker and monomer was chosen, the IOHP sensors responded to the urea solution with a concentration range of 0–30 mM and exhibited a linear range of 1–5 mM with a detection limit of 0.48 mM, which matched the actual demands. The IOHP sensors were applied to practical samples, and it was demonstrated that the recoveries reached ideal percentages of 94.7%–102%. All the results indicate that IOHP sensors are promising for opening a new route for the detection and elimination of urea.