Enzyme-free colorimetric detection of uric acid on the basis of MnO2 nanosheets-mediated oxidation of 3, 3?, 5, 5?- tetramethylbenzidine

MnO2 nanosheets (MnO2 NSs) were prepared and used as both oxidant of 3, 3 ', 5, 5 '- tetramethylbenzidine (TMB) and recognizer of UA, a simple colorimetric approach for sensitive detection of uric acid (UA) was established. In the medium of weak acid, MnO2 NSs exhibited strong oxidation capacity and could oxidize colorless TMB to generate a blue oxidation product (oxTMB) with an absorbance signal. However, the introduction of UA could inhibit MnO2 NSs -mediated TMB oxidation and reduce the formation of oxTMB, resulting in the blue fading and the absorbance weakening. Under the conditions of incubation time 20 min, pH 3.0, TMB 0.5 mM, and MnO2 NSs 50 mu M, the decrease in absorbance was linearly dependent on UA concentration in the range of 0.5-30.0 mu M with a detection limit of 0.21 mu M. Furthermore, the approach has been applied for determining UA in human urine samples with recoveries between 93.1 and 102.4 % and relative standard deviation less than 3.0 %.