Biosensor Calibration

The maximum concentration of substrate that can be measured with an enzyme electrode is related to AT . When the concentration is near to the linear relation between substrate concentration and the extent of enzyme reaction fails and a limiting value is reached. The 

Immobilization of the enzyme is thought to increase the value, the increase being related to change in substrate, diffusion effects, or changes in enzyme structure. 

The minimum concentration is often related to the minimum amount of electroactive substance that can be measured with the electrochemical transducer. 

The calibration graphs are therefore often S-shaped, leveling off at high concentration due to the or -related maximum concentration measurable and at low values by the performances of the transducer. The useful part of the curve is the linear zone where a variation in substrate concentration gives a variation in the signal of the transducer. The slope of the curve in this zone corresponds to the sensitivity of the biosensor because it expresses a variation in the signal obtained as a function of the analyte concentration. 

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Bayesian regularization 733 BDD 213 Beers e279 (Bio)composites 145 Biosensor calibration el73 Bioavailability 28, 47 Biochips 925 Biocomposite 358, 452 platforms 479... 

BIOSENSOR CALIBRATION AND METHYL MERCURY DETERMINATION IN STANDARD SOLUTIONS... 

Figure 10. Biosensor calibration curves for data obtained with phosphate buffer (a) GCE/PANI-PVS/HRP for H202 (-400 mV steady state amperometry, 300 rpm stirring, pH 7) (b) Au[PDMA-PSS/HRP for glyphosate (-100 mV, steady state amperometry, 400 rpm stirring, pH 6.1) (c) Au PANSA/CYP2D6 (-250 mV, DPV, pH 7.4) and (d) Pt PAM-PVS-PESA/HRP to H202 (-100 mV, CV, pH 6.5).

Some biosensors were designed to follow the different stages of a production line one by one, by semi-condnuous measurement. In this case, the biosensor is used with a system of flow injection analysis (FIA). Small sample volumes are used, and the problems of contamination in the fermentation industry can be avoided. There are also applications in biomedical analysis laboratories, where faster methods reduce the cost of each analysis. Finally, the automadon of FIA is possible using a microcomputer for data collection and management of the various steps of biosensor calibration and measurement. 

Inhibitors reduce the signal of a biosensor by reducing the activity of the immobilized enzyme on the transducer. This modifies a biosensor calibration curve that is plotted as a function of substrate concentration. As previously described (see 4.2.4.b), the curve is displaced according to the inhibition mode. The inhibitor is determined by fixing the substrate concentration and varying the inhibitor concentration. A new calibration curve is then plotted as a function of inhibitor... 

PSS-SG composite film was tested for sorption of heme proteins hemoglobin (Hb) and myoglobin (Mb). The peroxidaze activity of adsorbed proteins were studied and evaluated by optical and voltammetric methods. Mb-PSS-SG film on PG electrode was shown to be perspective for detection of dissolved oxygen and hydrogen peroxide by voltammetry with linear calibration in the range 2-30 p.M, and detection limit -1.5 p.M. Obtained composite films can be modified by different types of biological active compounds which is important for the development of sensitive elements of biosensors. 

A fiberoptic biosensor has been used for the determination of xanthine and hypoxanthine by immobilization of xanthine oxidase and peroxidase on different preactivated membranes, which were mounted onto the tip of the fiberoptic bundle [47], The hydrogen peroxide generated was measured using the luminol reaction. A linear calibration curve of the sensors occurred in the range of 1-316 nM hypoxanthine and of 3.1-316 nM xanthine, respectively, with a detection limit of 0.55 nM. 

For all these reasons, a microbial BOD-sensor needs to be calibrated before it can be used as a biochemical activity test. Only after a foregoing calibration procedure does a BOD-sensor finally reveal results which are both reliable and comparable to the conventional BOD5 method. Some consideration concerning the calibration of biosensors are given in Sect. 3.2.1.6. 

Here is an example from my research group s work on biosensors. The sensor has an electrode modified with a peptide that binds a target metal ion, which is then electrochemically reduced, the current being proportional to the concentration of metal. The electrode is calibrated with solutions of known concentration. Two experimental designs were used. The first was a two-level factorial design to find the effects of temperature, pH, added salt, and accumulation time. Spreadsheet 3.1 shows the design. 

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