Biosensors electrochemical immunosensors

Electrochemical sensors can be based on potentiometric, amperometric, or impedimetric transduction principles. Inherent benefits of electrochemical sensors include selectivity, ease of use, low Hmits of detection, and scope for miniaturization. Similar to biosensors, electrochemical immunosensors are also classified into potentiometric, amperometric, impedimetric, and conductometric based on the measured signal such as potential, current, impedance, and conductance, respectively. 

The material is presented in 17 chapters, covering topics such as trends in ion selective electrodes, advances in electrochemical immunosensors, modem glucose biosensors for diabetes management, biosensors based on nanomaterials (e.g. nanotubes or nanocrystals), biosensors for nitric oxide and superoxide, or biosensors for pesticides. 

In conclusion, electrochemical immunosensors are a useful class of biosensors that have taken advantage of some major developments during the past decades. 

To the best of our knowledge, the ideal reagent-free electrochemical immunosen-sor for on-the-spot analysis has yet to be developed. Systems reported in the literature as electrochemical immunosensors, some of which are listed and denoted by I under assay type in Table 2, are based primarily on one factor the immobilization of the sensing Ab or Ag directly on the electrode [124, 125]. The schematic of an electrochemical immunosensor, thus defined, is shown in Fig. 6. It should be noted that electrochemical immunosensors are often categorized as electrochemical biosensors, which covers any type of electrochemical sensor consisting of a biorecognition element placed directly over or in close proximity to the electrode [126]. 

Amperometric or voltammetric biosensors typically rely on an enzyme system that catalyt-ically converts electrochemically non-active analytes into products that can be oxidized or reduced at a working electrode. Although these devices are the most commonly reported class of biosensors, they tend to have a small dynamic range due to saturation kinetics of the enzyme, and a large overpotential is required for oxidation of the analyte this may lead to oxidation of interfering compounds as well (e.g., ascorbate in the detection of hydrogen peroxide). In addition to the use in enzyme-based biosensors, amperometric transducers have also been used to measure enzyme-labelled tracers for affinity-based biosensor (mainly immunosensors and genosensors). Enzymes which are commonly used for this purpose include horseradish peroxidase (HRP) [17] and alkaline phosphatase (AP) [18,19,21]. 

Monoamine oxidase amperometric biosensor based on SPE were also modified with MWCNT by using the drop casting technique for the determination of antidepressants in model solutions and dosage forms. The authors used BSA protein which provided a matrix for the immobilization of the enzyme and protection of the enzyme activity when glutaraldehyde is used as a linker. Serafin et aZ. developed a label free dual immunosensor for the determination of human growth and prolactin hormones. The electrochemical immunosensor was based on CNT modify carbon SPE platform with the presence of poly(ethylene-dioxythiophene) (PEDOT) and gold nanoparticles. Again, the hybrid nano-material composite facilitated a proper immobilization of the antibody on the electrode matrix. 

B. Piro, S. Reisberg, G. Anquetin, H.-T. Sue, M.-C. Pham,.Quinone-based polymers for label free reagentless electrochemical immunosensors applications to proteins, antibodies and pesticide detection. Biosensors, 3, 58-76 (2013). 

Figure 10.7 Schematic representation of the immunosensor proposed by Sanchez and co-workers, (a) Top view of the MWCNT/PSf screen printed device, (b) structure of MWCNT/PSf/IgG composite, (c) Cross section of the biosensor after incubation with anti-IgG-HRP antibody. (A) polycarbonate substrate, (B) insulator layer, (C) MWCNT/PSf. Reprinted with permission from Sanchez S, Pumera M, Fibregas E. Carbon nanotube/ polysulfone screen-printed electrochemical immunosensor. Biosensors and Bioelectronics 2007 23 332--40, 2007 Elsevier, BV.

Wan Y, et al. Carbon nanotube-based ultrasensitive multiplexing electrochemical immunosensor for cancer biomarkers. Biosensors Bioelectronics 2011 30 93-9. http //dx.doi.org/10.1016/j. bios.2011.08.033. 

Li H, et al. Electrochemical immunosensors for cancer biomarker with signal amplification based on ferrocene functionalized iron oxide nanoparticles. Biosensors Bioelectronics 2011 26 3590-5. http //dx.doi.Org/10.1016/j.bios.2011.02.006. 

The formation of PPy on an electrode surface provides a nanoporous matrix that is highly used for the immobilization of biomolecules to design various biosensors (electrochemical biosensor, immunosensor, and DNA sensor). It also acts as a mediator to transfer the analytical signal generated by some redox enzymes to the transducer even if the redox center is deeply buried in the protein globule. In addition, it is an efficient protector of electrodes against interfacing materials (proteins present in real samples such as blood and urine). 

Chapter 4 presents the recent advances in antibodies research and their applications for immunosensor development. Electrochemical immunosensors for metaUoproteins, nonmetaUoproteins, and cancer cells using their specific antibodies are emphasized. In Chapter 5, the essential components for the development ofbiosensors instrumentation are discussed. Virtual electrochemical instrumentation development using labVIEW is presented. Also, hand held microcontroUer-based electrochemical biosensors are assembled and applied for the measurement of various biomarkers including cytochrome c and nitric oxide metabohtes. These chapters provide the essential background knowledge and up-to-date advances in this field. The book should thus serve as an introductory text for those who intend to specialize in either the theoretical or practical apphcations. It is hoped that this textbook will be a fruitful launch pad for many careers in biosensors and bioelectronics. 

Electrochemical immunosensors combine high sensitivity of electrochemical methods and simple and miniature construction of the required instrumentation with excellent specificity of antibodies as recognition elements. The current status of this approach applied for environmental analysis will be discussed. The various types of biosensors were generally found very suitable for environmental analysis/ and the subgroup of immunosensors provided numerous attractive applications in this field, too. However, as a relatively novel technology, the biosensors and bioanalytical techniques generally compete with the established methods of classic instmmental analysis." ... 

Particularly attractive for numerous bioanalytical applications are colloidal metal (e.g., gold) and semiconductor quantum dot nanoparticles. The conductivity and catalytic properties of such systems have been employed for developing electrochemical gas sensors, electrochemical sensors based on molecular- or polymer-functionalized nanoparticle sensing interfaces, and for the construction of different biosensors including enzyme-based electrodes, immunosensors, and DNA sensors. Advances in the application of molecular and biomolecular functionalized metal, semiconductor, and magnetic particles for electroanalytical and bio-electroanalytical applications have been reviewed by Katz et al. [142]. 

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