Colorimetric sensing platform based on MnO2 nanosheets for the detection of reducing substances and alkaline phosphatase activity in whole Hela cells

Abstract The development of efficient methods for alkaline phosphatase (ALP) activity assay is of great importance in clinical diagnosis and many biomedical applications. In this work, the authors create two strategies for colorimetric detection of ALP activity. The first strategy is developed by using directly manganese dioxide (MnO 2 ) nanosheets as colorimetric probes. The second strategy is developed by using MnO 2 and the chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) as colorimetric probes based on the catalytic reduction of oxidized TMB. The first strategy has a linear response in 10 U L −1 to 80 U L −1 with 3.0 U L −1 detection limit while the second one has a linear response in 7 U L −1 to 100 U L −1 with 0.05 U L −1 detection limit. The method based on MnO 2 -TMB which have lower detection limit and higher sensitivity was applied to monitor ALP activity in whole Hela cells lysate. In addition, based on redox properties, MnO 2 -TMB sensing system was successfully used in detecting reducing substances such as ascorbic acid, Na 2 S and so forth. Conceivably, MnO 2 -TMB sensing system is not limited to ALP activity assay but has a wide scope to be applied in assays of the total antioxidant capacity of dietary substances and biological fluids. Graphic Abstract Two strategies were created for colorimetric detection of ALP activity: The first strategy is developed by using directly manganese dioxide (MnO 2 ) nanosheets as colorimetric probes, and the second strategy by using MnO 2 and the chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) as colorimetric probes based on the catalytic reduction of oxidized TMB.