Electron transfer mediated biosensor with plasma-polymerized film containing redox site

摘要

An amperometric mediator enzyme biosensors for detection of blood sugar are the most popular and commercialized biosensors, which help type II diabetes mellitus patients to monitor their daily sugar level. The electron mediator plays a role as the medium for electron transfer between the catalytic center of the enzyme and the electrode. Then, the effective electronic signal which is proportional to the glucose concentration is obtained without influence of oxygen concentration nor obstacle by electrochemical species such as ascorbic acid. A ferrocene is a typical mediator for enzyme biosensors. Usually, the enzyme and mediators are embedded or immobilized in/onto a cast polymer on an electrode surface. The integrated design for sensor device between enzyme and redox site strongly influences the sensor characteristics. Therefore, the many strategies for the electron transfer system have been proposed. However, it is not easy to design for practical use. Firstly, it is need to be complicated fabrication process such as the synthesis of polymer and immobilization of enzyme. Secondly, it needs to tune the wettable balance between hydrophobic redox site of ferrocene and hydrophilic enzyme. The plasma polymerization film (PPF) is achieved by glow discharge or plasma in a vapor phase. The properties of the PPF film include (a) the ability to be made extremely thin (< 1 μm), (b) the good adhesion to any substrate, (c) the pin-hole-free and flat surface structure, (d) the mechanical and chemical stability (a result of its highly-branched and cross-linked structure), and (e) the capability to accommodate a large amount of biomaterials, such as enzymes, antibodies, and oligonucleotide which can be immobilized onto the surface of the film. We propose a new strategy for the fabrication of mediator biosensor, based upon PPF. Although there are some reports of plasma-polymerized dimethylaminomethylferrocene (DMAMF), its application for mediator biosensor has not been reported. The DMAMF is probably a suitable monomer for biosensor design based on PPF, firstly because vaporization of DMAMF is easier than the other monomer containing ferrocene such as ferrocene, vinylferrocene, and ferrocene acetontrile, and secondly because the DMAMF PPF has amino groups which enable a large amount of enzyme to be immobilized. In this article, we present the characterization and usefulness of amperometric enzyme biosensor based on mediated electron transfer of DMAMF PPF.