In
this research, we attempted to develop a sensitive colorimetric
sensing strategy for the detection of acid phosphatase (ACP) based
on MnO2 nanosheets and explored its applications in screening
and evaluating inhibitors of ACP. The MnO2 nanosheets exhibit
intrinsic biomimetic oxidase activity, which can catalyze the oxidation
of the colorless 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonate)
diammonium salt (ABTS) into green oxidized ABTS (oxABTS). Upon the
introduction of ACP, l-ascorbic acid-2-phosphate can be dephosphorylated
to ascorbic acid, which arouses the disintegration of MnO2 nanosheets into Mn2+ ions. This disintegration weakens
the enzyme mimicking activity of the MnO2 nanosheets, leading
to the impediment of the oxidation of ABTS. Conversely, in the absence
of ACP, the ABTS is rapidly oxidized by MnO2, leading to
a significant colorimetric signal change. The absorbance difference
at 420 nm displayed a linear relationship with the concentration of
ACP ranging from 0.075 to 0.45 mU·mL–1, generating
a detection limit of 0.046 mU·mL–1. In the
inhibition assays, this sensing platform provided simple detection
for parathion-methyl (PM), a representative inhibitor of ACP. The
facile evaluation of the inhibitory effect of PM, including its IC50
toward ACP, was also realized.