Fabrication of nanoporous nanocomposites entrapping Fe3O4 magnetic nanoparticles and oxidases for colorimetric biosensing.

A nanostructured multicatalyst system consisting of Fe(3)O(4) magnetic nanoparticles (MNPs) as peroxidase mimetics and an oxidative enzyme entrapped in large-pore-sized mesoporous silica has been developed for convenient colorimetric detection of biologically important target molecules. The construction of the nanocomposites begins with the incorporation of MNPs on the walls of mesocellular silica pores by impregnating Fe(NO(3))(3)·9H(2)O, followed by the immobilization of oxidative enzymes. Glutaraldehyde crosslinking was employed to prevent enzymes leaching from the pores and led to over 20 wt% loading of the enzyme. The oxidase in the nanocomposite generates H(2)O(2) through its catalytic action for target molecules and subsequently activates MNPs to convert selected substrates into colored products. Using this strategy, two different biosensing systems were constructed employing glucose oxidase and cholesterol oxidase and their analytical capabilities were successfully verified by colorimetrically detecting the corresponding target molecules with excellent selectivity, sensitivity, reusability, and stability. Future potential applications of this technology range from biosensors to multicatalyst reactors.