Amperometric metabolic sensors

On the other hand, the molecular recognition by enzymes, which are also applied in the form of organelles, microorganisms and tissue slices, is accompanied by chemical conversion of the analyte to the respective products. Therefore this type of sensor is termed a metabolism sensor2. The initial state is usually reached when the analyte conversion is complete. With metabolism sensors, under certain conditions cosubstrates, effectors, and enzyme activities can be measured via substrate determination. Amperometric and potentiometric electrodes and thermistors are the preferred transducers, but in some cases optoelectronic sensors have also been used. With biomimetic sensors physical signals such as sound, stress, or light are measured through their ability to... 

Konig et al. [80-84] demonstrated that microbial sensors are suitable for the summary quantification of nitrifiable compounds (see also Sect. 3.3.1) as well as for the detection of nitrification inhibiting effects. Such biosensors, which contain a mixed population of the nitrifying bacteria Nitrosomonas sp. and Nitrobacter sp., exhibit a specific supplementary metabolic capacity. This enables the amperometric determination of ammonia according the following scheme of nitrification ... 

New developments in this area include uric acid sensors based on the mediation of urate oxidase by a novel redox polymer, poly(N-methyl-o-phenylenediamine) [145], and by the freely diffusing mediator 1-methoxy-5-methylphenazinium [146], continued research on the direct amperometric detection of NADH [147] and the use of redox mediators [148] for dehydrogenase enzymes, to allow practical sensors that exploit this large class of enzymes, and the use of cytochrome P450-modified glassy carbon electrodes as drug metabolism biosensors [149]. 

A sensor array for monitoring indicators of mannnalian cell metabolic status has been reported by Pemberton et al. [33], and is based on both enzyme-modified elements and chemical sensors for temperature, pH, and dissolved oxygen. The array, fabricated in a silicon platform using MEMS technology, consists of five-well sensor strips with a multipotentiostat to switch between potentiometric and amperometric measurement modes. Screen-printed biosensors for glucose and lactate were grafted onto two of the weUs. The authors envision applications to cell culture and cytotoxicity studies. 

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