Human serum albumin templated MnO₂ nanosheets as an efficient biomimetic oxidase for biomolecule sensing

Herein, we have proposed a colorimetric biosensor for detection of acid phosphatase based on human serum albumin (HSA) templated MnO2 nanosheets (HSA-MnO2 NSs). HSA-MnO2 NSs as an efficient biomimetic oxidase could catalyze the oxidization of 3,3',5,5'-tetramethylbenzidine (TMB) to the coloured oxidation product (oxTMB). Acid phosphatase (ACP) could hydrolyze l-ascorbic acid-2-phosphate (AAP) to produce ascorbic acid, and ascorbic acid could lead to the decomposition of MnO2 NSs to Mn2+ ions, inhibiting the production of oxTMB. On the basis of this, we have demonstrated a novel colorimetric approach for the detection of acid phosphatase with the linear range from 50 μU mL-1 to 1500 μU mL-1 and a detection limit of 40 μU mL-1. The MnO2 NS-based colorimetric method has been successfully used to determine the content of acid phosphatase in real samples with satisfactory results.