Accelerating the peroxidase-like activity of Co2+ by quinaldic acid: Mechanism and its analytical applications

Although enzyme mimics have been widely developed, limited catalytic efficiency is still a bottleneck, especially under neutral condition. Herein, we reported the bioactive quinaldic acid (QA) significantly boosted the peroxidase-like activity of Co2+ in the presence of bicarbonate (HCO3-). With 2,2 '-azino-bis-(3-ethyl-benzothiazoline-6-sulphonate) (ABTS) as the substrate, the catalytic activity of Co2+ (1 mu M) was increased by over 300 times upon adding 100 mu M QA. The formed Co2+ complex had much higher turnover number (5.52 min(-1)) than that of cobalt-based nanozymes (0.011-0.51 min(-1)) in decomposing H2O2. Based on this system, ultrasensitive colorimetric methods for the detection of Co2+, bicarbonate and urease activity were achieved with limits of detection of 4.6 nM, 40 mu M and 0.00125 U/mL, respectively. For the first time, this work established an ultrasensitive method for the detection of urease activity by activating a peroxidase-like mimic with the pro-duced HCO3-.