Dual-functionalized porous Si/hydrogel hybrid for label-free biosensing of organophosphorus compounds.

A multifunctional porous Si (PSi) nanostructure is designed to combine a responsive PSi/hydrogel hybrid interfaced with a biorecognition element to selectively recognize small model molecules, organophosphorus compounds (OPCs), of high biological importance. A pH-responsive poly(2-dimethylaminoethyl methacrylate) [poly(DMAEMA)] hydrogel is synthesized and patterned in situ within an oxidized PSi Fabry-Pérot thin film. The resulting new hybrid displays a well-defined, rapid, and reversible optical response to pH changes. We employ this hybrid as an optical transducer element in a biosensing scheme by integrating it with organophosphorus hydrolase (OPH), capable of selective OPC hydrolysis. The enzyme is immobilized onto the pore walls of the oxidized PSi scaffold, resulting in an array of catalytic nanoscale chambers for the degradation of OPCs. Thus, the biosensor function relies on diffusion of the OPCs hydrolysis products from the catalytic chambers, through the interconnected pores network, to the hybrid region triggering its optical response. Exposure to the model target analyte results in a rapid and reproducible change in the optical reflectivity spectrum of the hybrid, allowing for label-free detection and quantification of OPCs in a simple and reliable manner.