SOL-GEL-DERIVED THICK-FILM AMPEROMETRIC IMMUNOSENSORS

Sol-gel processing is used for the first time for the preparation of e lectrochemical immunosensors. One-step sensor fabrication, based on th e coupling of sol-gel and screen-printing technologies, is employed. A low-temperature cured ink is prepared by dispersion of rabbit immunog lobulin G (RIgG), graphite powder, and a binder in the sol-gel solutio n. The enzyme-labeled antibody can readily diffuse toward the encapsul ated antigen, which retains its binding properties, and the associatio n reaction is easily detected at the dispersed graphite surface. Use o f anti-RIgG labeled with alkaline phosphatase, naphthyl phosphate as t he substrate, and amperometric detection at +400 mV (vs Ag/AgCl) resul ts in a low detection limit of 5 ng/mL (32 pM) for the solution antige n. Tailoring the porosity of the ceramic-carbon matrix can be used for tuning the assay performance. The high sensitivity, low cost, durabil ity, and simplicity of the new single-use immunosensors make them well suited for various onsite applications.