Fabrication of an inorganic–organic hybrid based on an iron-substituted polyoxotungstate as a peroxidase for colorimetric immunoassays of H2O2 and cancer cells

Fabrication of a folate and iron-substituted polyoxometalate [(FeOH2)2SiW10O36] has been achieved through self-assembly of folate and polyoxometalate molecules, which was characterized by IR spectroscopy, and transmission electron microscopy (TEM). This inorganic–organic hybrid has been proven to possess intrinsic peroxidase-like activity in the oxidation of dyes, which can catalyze oxidation of the peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2 to form a blue color in aqueous solution. The TMB/POM/H2O2 system provides a new approach to detect H2O2 with good sensitivity, wide linear range (from 1.34 × 10−7 to 6.7 × 10−5 mol L−1), low detection limit (1 × 10−7 mol L−1) and fast response towards H2O2 instead of an enzyme biosensor. In addition, this unique hybrid FA–Fe2SiW10 is inexpensive, easily prepared, and very efficient in the colorimetric multiplexed immunoassay of cancer cells.