Process biosensor analysis

Biosensors may provide the basis for in-field analyses and real-time process analysis. However, biosensors are generally limited to the determination of a limited range of analytes in defined matrices. Enzyme-based biosensors, principally acetylcholinesterase (AChE) inhibition, have been successfully used in environmental analysis for residues of dichlorvos and paraoxon, " carbaryl " and carbofuran. " Immunochemically based biosensors may be the basis for the determination of pesticide residues in liquid samples, principally water and environmental samples, but also fruit juices. The sensors can be linked to transducers, for example based on a piezo-... 

Bioanalyzer can be considered another version of commercial biosensors for off-line analysis. It was developed to have capabilities of complete analysis, short response time, specificity, and sensitivity that allows a quick clinical test. Abbott Vision, Boehringer-Mannheim Reflectron, and Kodak Ektachem DT60 (IBI Biolyzer is the new name) are used for cholesterol measurement in doctors offices. Bioanalyzer consists of biological and transducing component that are not physically connected. The uniqueness of this separation provides the versatility of analysis, i.e., use of disposable and different biological component for multi-components measurements. In authors laboratory, Kodak Ektachem DT60 was used successfully to determine cholesterol in some food matrices as well as in off-line process control. The analysis time was only 10 minutes compared to 1-2 days for the GC and HPLC methods. Complicated... 

However, problems associated with the reproducibility between electrodes derived from the screen-printing process and the partial electrode fouling have compromised the sensitivity of the biosensors. Work is in progress to improve both the reproducibility and the limits of detection by the use of new types of electrodes. The toxin overestimation observed with the amperometric biosensor, in the case of the microcystin analysis, suggests the use in parallel to other analytical techniques in order to minimise the risk of false-positive results. Nevertheless, the electrochemical strategy is appropriate to discriminate between toxic/non-toxic samples. 

The use of novel electrode materials should, in principle, improve the reproducibility of the biosensor, since the screen-printing process is thought to be responsible for the standard deviation of the electrochemical measurements. The developed biosensor can also be applied to the analysis of water. In this case, the matrix is expected to produce fewer effects. Finally, the use of molecularly engineered supersensitive enzymes and the combination with signal amplification systems can contribute to increase the sensitivity of the biosensor. 

Redox enzymes are the active component in many electrochemical enzyme electrode biosensor devices.1821 The integration of two different redox enzymes with an electrode support, in which one of the biocatalysts is photoswitchable between ON and OFF states, can establish a composite multisensor array. The biomaterial interface that includes the photoswitchable enzyme in the OFF state electrochemi-cally transduces the sensing event of the substrate corresponding to the nonphoto-switchable enzyme. Photochemical activation of the light-active enzyme leads to the full electrochemical response, corresponding to the analysis of the substrates of the two enzymes. As a result, the processing of the signals transduced by the composite biomaterial interface in the presence of the two substrates permits the assay of the... 

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