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

Abstract

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.