Biosensors function

FIGURE 7.3 Simplified equivalent circuit of an original (unmodified) EIS structure (a) and EIS biosensor functionalized with charged macromolecules (b). Cj, Cx and CML are capacitances of the gate insulator, the space-charge region in the semiconductor, and the molecular layer, respectively / u is the resistance of... 

Many different types of techniques for protein immobilization have been developed using, in most cases, enzyme sensors. Early studies of enzyme biosensors often employed thick polymer membranes (thickness 0.01-1 mm) in which enzymes are physically entrapped or chemically anchored. The electrode surface was covered with the enzyme-immobilized polymer membranes to prepare electrochemical enzyme sensors. Although these biosensors functioned appropriately to... 

The Effect of the Foreign Body Reaction on Chronic Biosensor Function... 

Figure 3.2 The effect of prolonged subcutaneous implantation on biosensor function. Blood glucose values shown in solid circles and glucose sensor values in the continuous lines. The early study (top panel), but not the late study (bottom), shows excellent sensor accuracy and minimal lag between blood glucose and sensed glucose values. MARD (mean absolute relative difference) refers to a sensor accuracy metric. EGA refers to the Clarke error grid analysis accuracy metric.

Biosensors, functional concept using bloactlve substances, 464,465f... 

Salomon, S., Leichle, T., Dezest, D., Seichepine, R, Guillon, S., Thibault, C., Vieu, C., Nicu, L., 2012. Arrays of nanoelectromechanical biosensors functionalized by microcontact printing. Nanotechnology 23 (49), 495501. 

Functionalized conducting monomers can be deposited on electrode surfaces aiming for covalent attachment or entrapment of sensor components. Electrically conductive polymers (qv), eg, polypyrrole, polyaniline [25233-30-17, and polythiophene/23 2JJ-J4-j5y, can be formed at the anode by electrochemical polymerization. For integration of bioselective compounds or redox polymers into conductive polymers, functionalization of conductive polymer films, whether before or after polymerization, is essential. In Figure 7, a schematic representation of an amperomethc biosensor where the enzyme is covalendy bound to a functionalized conductive polymer, eg, P-amino (polypyrrole) or poly[A/-(4-aminophenyl)-2,2 -dithienyl]pyrrole, is shown. Entrapment of ferrocene-modified GOD within polypyrrole is shown in Figure 7. 

In Vivo Biosensing. In vivo biosensing involves the use of a sensitive probe to make chemical and physical measurements in living, functioning systems (60—62). Thus it is no longer necessary to decapitate an animal in order to study its brain. Rather, an electrochemical biosensor is employed to monitor interceUular or intraceUular events. These probes must be small, fast, sensitive, selective, stable, mgged, and have a linear response. 

In this biosensor a quartz radio crystal is functionalized with the enzyme glucose-6-phosphate dehydrogenase. As shown in Figure 3, a thin film of Pmssian blue [14038-43-8] C gN gFe, is then coated onto the crystal. 

Electrical conductivity measurements revealed that ionic conductivity of Ag-starch nanocomposites increased as a function of temperature (Fig.l7) which is an indication of a thermally activated conduction mechanism [40]. This behavior is attributed to increase of charge carrier (Ag+ ions) energy with rise in temperature. It is also foimd to increase with increasing concentration of Ag ion precursor (inset of Fig.l7). This potentiality can lead to development of novel biosensors for biotechnological applications such as DNA detection. 

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