We report a method for determining dopamine in serum via colorimetric sensing. This new method adopts bromelain-templated MnO2 nanosheets that possess high oxidase activity. 3,3 ',5,5 '-Tetramethylbenzidine (TMB) can be directly oxidized by bromelain-MnO2 nanosheets to oxTMB products. Without dopamine, the absorbance at 652 nm (A(652)) of oxTMB products is significantly enhanced. Upon the addition of dopamine, oxidase activity is markedly inhibited because the lamellar structure decomposes to generate Mn2+ ions, and the A(652) value gradually decreases. Moreover, the oxidation process of dopam...
