Glucose sensor principle

Kakehi N, Yamazaki T, Tsugawa W, Sode K. 2007. A novel wireless glucose sensor employing direct electron transfer principle based enzyme fuel cell. Biosens Bioelectron 22 2250-2255. 

Schmid et al. used the same principle to develop sensors to be incorporated into FI systems for the determination of ascorbic acid in fruit juices [38] and that of lactic acid in dairy products [39]. The membrane used in both applications consisted of decacyclene dissolved in silicone rubber that was treated similarly as the membrane in glucose sensors (Fig. 3.4.B). The oxygen optrode was coated with a sheet of carbon black as optical insulation in order to protect it from ambient light or intrinsic sample fluorescence. Ascorbic acid oxidase or lactic acid oxidase was immobilized by adsorbing it onto carbon black and cross-linking it with glutaraldehyde. The FI system automatically buffered and diluted the food samples, thereby protecting the biosensor from a low pH and interferents. 

Figure 30. Principle of the D-glucose sensor based on the Na /D-glucose cotransporter-embedded BLM (reprinted with permission from Anal. Chem. 1993, 65, 364. Copyright 1993 American Chemical Society).

Despite successful proof of principle that NO-releasing materials can be employed to fabricate a functional glucose sensor, the toxicity of the particles that leached from the polymer membrane remained a concern. Additionally, the amount and the duration of NO release were limited by the mass of the particles in the polymer film. Upon device miniaturization, the NO release may not prove sufficient to sustain biocompatibility. Two alternative strategies were explored to address these... 

Electron conducting polypyrrole BLMs have been used for developing glucose sensors [80]. Similarly, s-BLMs have been employed for the same purpose. The same principle was recently used to prepare a simple and fast... 

As mediators different molecules can be applied, e.g. ferrocene, mthenium (111) hexamine or tetrathiafulvalene, which are reoxidized on an electrochemical electrode, preferably carbon (Cass et al. 1984). Such electrochemical working principle allows the miniaturization of a biosensor using screen-printed or thin-film electrodes with adsorbed or immobilized enzymes also facilitating mass production for creating disposable glucose sensors with revenues of several million euros per anno. 

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