Catalytic biosensors

PANI/PS composite nanolibers, prepared by electrospinning technique, were employed to detect by means of cyclic voltammetry [157], Composite nanofibers exhibited superior sensing properties for corresponding to composite thin films. The enhanced sensitivity of the composite nanofibers was attributed to their large surface area and good electrical properties. 

Lakard et al. have described HRP modified PANI nanoparticles-based biosensor for sensing [159]. This biosensor format exhibits improved enzyme deposition and improved signal-to-noise ratio. There is a strong relationship between nano-dimension and biosensing performance. 

GOX could also be incorporated into aligned CNT/PPy composite nanofibers with Fe nanoparticles on the tip of CNTs [161]. Inclusion of Fe nanoparticles was the key factor to reduce the potential of the redox reaction of H O. A near linear increase in the current up to 20 mM 

The sensitivity and response time of a nanojunction-based glucose sensor is reported to be 1 nA/mM and the response time is less than 1 s. The features are essential for an in vivo device for real-time monitoring of glucose levels. 

Normal human blood plasma contains 130-260 mg cholesterol per 100 ml, of which two-thirds is esterified with fatty acids and one-third is present as sterol [165]. Estimation of cholesterol has attracted much attention as the increased level of blood cholesterol is directly related to coronary heart diseases such as hypertension, atherosclerosis, and myocardial infarction. The CP nanocomposites have provided a suitable pathway for the operation of the biosensor by immobilization of the biomolecule on CP for detection of different analytes. A smart, quick, accurate determination of cholesterol in blood is an urgent need in clinical diagnosis. The following biochemical reaction occurs as a result of interaction of cholesterol oxidase (ChOx) with cholesterol  

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Catalytic biosensors, 3 796-799 Catalytic chain transfer polymerization (CCTP), 20 442, 444... 

A biosensor is a sensing device that is integrated within or intimately associated with a physical transducer. Such a system quantifies electronic signals arising from the interaction between a biosensor and an analyte of interest. Catalytic biosensors use enzymes, microorganisms, or whole cells to catalyze a reaction with the target analyte, while affinity biosensors utilize antibodies, receptors, or nucleic acids to bind with the target analyte. 

The development of conducting polymer (CP) nanocomposites has opened up novel fundamental and applied frontiers. The present chapter overviews recent works dealing with synthesis, characterization of CP nanocomposites, and then-applications related to biosensors. Various synthesis strategies, mechanism, and process parameters along with their characterization techniques are discussed. Some potential areas for biosensor-related applications of CP nanocomposites are highhghted, including catalytic biosensors and bioaffinity biosensors. 

A. Catalytic biosensors These are kinetic devices that measure steady-state concentration of a transducer-detectable species formed/lost due to a biocatalytic reaction. 

The most popular catalytic biosensor in clinical analysis is a glucose sensog used in monitoring the blood sugar of diabetes patients. The biological component often used GOD. 

ALP + bienzymatic biosensor (tyrosinase. CDH) Phenyl phosphate PhenoP Bienzyme catalytic biosensor with a Clark O2 electrode, 0.60 mV vs. Ag/AgCl E 3.2fM (320 zmole), T = 57 min 23... 

Signal generation binding biosensor (by binding of the analyte), catalytical biosensor (by conversion of an auxiliary substance), metabolic (enzymatic) biosensor (by conversion of the analyte to reaction product)... 

The action of catalytical biosensors is associated with substrate diffusion into biocatalytical membrane and its conversion to a product. The simulation of biosensor action includes solving the diffusion equations for substrate and product with a term containing a rate of biocatalytical transformation of substrate. The complications of modeling arise due to solving partially differential equations with nonlinear biocatalytical term and with complex boundary and initial conditions [6, 7]. 

VACNT electrodes have been successfully employed with different immobilised biological materials, such as enzymes (catalytic biosensors) and antibodies or DNA (affinity biosensors), for the development of electrochemical biosensors. The characteristics of these different electrochemical biosensors are discussed in the next sections. 

The preparation approaches described above are also convenient for the encapsulation of enzymes into the sol-gel nanocomposites to develop enzyme catalytic biosensors. For instance, Bharathi and Lev [27] mixed the glucose oxidase enzyme solution with gold nanoparticles in a methyl silicate sol and then coated the mixture suspension on a substrate for glucose sensing. In another example, silica matrices were impregnated with Au nanoparticles and horseradish peroxidase to obtain a glucose sensor [25]. 

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