Reagentless biosensors

Reagentless biosensors - biosensors Real electrode area - electrode surface area Real part of impedance impedance... 

This review is a survey of the research on the direct electron transfer (DET) between biomolecules and electrodes for the development of reagentless biosensors. Both the catalytic reaction of a protein or an enzyme and the coupling with further reaction have been used analytically. For better understanding and a better overview, this chapter begins with a description of electron transfer processes of redox proteins at electrodes. Then the behaviour of the relevant proteins and enzymes at electrodes is briefly characterized and the respective biosensors are described. In the last section sensors for superoxide, nitric oxide and peroxide are presented. These have been developed with several proteins and enzymes. The review is far from complete, for example, the large class of iron-sulfur proteins has hardly been touched. Here the interested reader may consult recent reviews and work cited therein [1,19]. 

Figure 1.6 describes what reagentless biosensor structures based on mediated ET can look like. 

Figure 1.6 Schematic representation of reagentless biosensors (a) ET via conductive polymer chains (b) ET via redox-relay modified polymer chains.

The general advantages of reagentless biosensor structures can be summarized as follows. Since all components of the assay are securely immobilized on the electrode surface, there is no or just a negligible loss of redox mediators, cofactors, and/or enzymes over the time of operation. This is of importance for the performance and safety of a device because the impact of free-diffusing possibly toxic substances is minimized. Therefore, reagentless biosensor architectures are often used for in vitro and in vivo measurements as outlined in Sec lion 1.4.5. 

One successful strategy to improve ET rates between enzyme and electrode is the modification of conducting polymers with redox mediators in order to obtain reagentless biosensors [11, 270, 271, 292-299]. The drawback of electropolymerization of conducting polymers is that the reaction is sensitive to oxygen, which complicates fabrication at the industrial scale. 

Schuhmann, W., Zimmermann, H., Habermtiller, K., and Laurinavicius, V. (2000) Electron-transfer pathways between redox enzymes and electrode surfaces reagentless biosensors based on thiol-monolayer-bound and polypyrrole-entrapped enzymes. Faraday Discussions, 116, 245-255. 

Conducting polymer-based amperometric enzyme electrodes towards the development of miniaturized reagentless biosensors. Synthetic Metals, 61 (1-2), 31-35. 

Habermtiller, K., Reiter, S., Buck, H., Meier, T., Staepels, J., and Schuhmann, W. (2003) Conducting redox polymer-based reagentless biosensors using modified PQQ-dependent glucose dehydrogenase. Microchimica Acta, 143 (2-3), 113-121. 

Liu H, Ying T, Sun K et al. A reagentless biosensor highly sensitive to hydrogen peroxide based on new methylene blue N dispersed in Nafion gel as the electron shuttle. J Electroanal Chem 1996 417 59-64. 

D. E. Benson, Reagentless biosensors based on nanopartlcles,ln Nanomaterials for Biosensors [Ch. Kumar, ed.), Wiley-VCH, Weinheim [2008). 

Direct Electron Transfer between Redox Enzymes and Electrodes As already pointed out, reagentless biosensors making use of a direct communication between the enzyme and the transducer... 

Sassolas A, Blum LJ, Leca-Bouvier BD (2009) Polymeric luminol on pre-treated screen-printed electrodes for the design of peiformant reagentless biosensors. Sens Actuators, B 139(1) 214-221. doi 10.1016/j.snb.2009.01.020... 

Schuhmann, W., Huber, J., Kranz, C., and Wohlschalger, H., Conducting polymer-based amperometric enzyme electrodes. Towards the development of miniaturized reagentless biosensors, Synth. Met., 61. 31-35 (1994). 

A. Narvaez, G. Suarez, I. C. Popescu, I. Katakis, E. Dommguez, Reagentless Biosensors based on Self-deposited Redox Polyelectrolyte-oxidoreductases Architectures. Biosens. Bioelectron., 15 (2000) 43-52. 

In contrast to GOD, some enzymes such as IIRP can undergo direct electron transfer with unusual facility. For this reason, no mediator was required when those enzymes were used [100, 105, 107, 108]. In general, the sensitivity of the detection of a target substrate could be significantly improved by the use of a mediator. For the construction of reagentless biosensors, it is necessary to immobilize the mediator together with an en me inside the polymer film. So, ferrocene [74,104, 109, 111], quinone and related compounds [106], redox dye [97], and mono- [102] and bipyridinium [92-94, 96] have been incorporated into ECP films. 

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