Immunosensors electrochemical

For a DC measurement, what type of interface would that have to be, ideally polarized or nonpolarized Would the same restriction apply in the case of an AC measurement  

It has been said that interfaces separate charges. Explain the charge separation and draw the equivalent circuit diagram of the following materials interfacing with an electrolyte containing only NaCl and water. 

In the round insert of Fig. 5.1, we see that at least two equilibrium potentials exist in the aqueous solution of any redox couple. Yet there can be only one potential at any given electrode. How do you explain this apparent discrepancy  

Teresa Ferndndez-Abedul, M. Begom Gonzdlez-Garcia andAgusUn Costa-Garda Departamento de Qufmica Ftsica y AnaUtica, Facultad de Qufmica, Universidad de Oviedo, 33006, Oviedo, Julidn Claverla, 8, Spain 

Various definitions have been given to the word biosensor. The journal Biosensors and Bioelectronics defines a biosensor as an analytical device incorporating a biological material, a biologically derived material, or a biomimic, intimately associated with or integrated 

Edited by Alberto Escarpa, Marfa Cristina Gonzalez and Miguel Angel L6pez. 2015 John Wiley Sons, Ltd. Published 2015 by John Wiley Sons, Ltd. 

Special peaks (such as this in 2008), a rate of 151 and 67 publications per year is observed for Scopus and Google Scholar, respectively. 

As it can be seen, the number of publications is enormous. The aim of this chapter, rather than attempting a systematic review of the field, is to show in a didactic manner the possibilities of electrochemical immunosensing for food analysis. There are some parts that could be found in other chapters of this book, such as, for example, the use of miniaturized electrodes, nanomaterials, or electrochemical techniques. However, a focus on the knowledge required for understanding their application to food analysis is always made, leaving a deeper treatment for those chapters. On the other hand, the reader can find many important references to the field in recent reviews, from the most general to the particular ones. Thus, recent trends in antibody-based sensors [2] (immunosensors) or smart electrochemical biosensors (from advanced materials to ultrasensitive devices) 

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Explain clearly how the use of enzymes can enhance the power of electrochemical immunosensors. 

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. 

M.A. Lopez, F. Ortega, E. Dominguez, and I. Katakis, Electrochemical immunosensor for the detection... 

R.W. Keay and C.J. McNeil, Separation-free electrochemical immunosensor for rapid determination of... 

Competitive immunoassays may also be used to determine small chemical substances [10, 11]. An electrochemical immunosensor based on a competitive immunoassay for the small molecule estradiol has recently been reported [11]. A schematic diagram of this immunoassay is depicted in Fig. 5.3. In this system, anti-mouse IgG was physisorbed onto the surface of an SPCE. This was used to bind monoclonal mouse anti-estradiol antibody. The antibody coated SPCE was then exposed to a standard solution of estradiol (E2), followed by a solution of AP-labeled estradiol (AP-E2). The E2 and AP-E2 competed for a limited number of antigen binding sites of the immobilized anti-estradiol antibody. Quantitative analysis was based on differential pulse voltammetry of 1-naphthol, which is produced from the enzymatic hydrolysis of the enzyme substrate 1-naphthyl phosphate by AP-E2. The analytical range of this sensor was between 25 and 500pg ml. 1 of E2. 

The development of electrochemical immunosensors generally involves the immobilization of an immunocomplex on a single electrode, followed by detection via the... 

O.A. Sadik and J.M. van Emon, Applications of electrochemical immunosensors to environmental monitoring. Biosens. Bioelectron. 11, i-xi (1996). 

R.M. Pemberton, T.T. Mottram, and J.P. Hart, Development of a screen-printed carbon electrochemical immunosensor for picomolar concentrations of estradiol in human serum extracts. J. Biochem. Biophys. Methods 63, 201-212 (2005). 

S. Viswanathan, L.-C. Wu, M.-R. Huang, and J.-A.A. Ho, Electrochemical immunosensor for cholera toxin using liposomes and poly(3,4-ethylenedioxythiophene)-coated carbon nanotubes. Anal. Chem. 78, 1115-1121 (2006). 

M. Akram, M.C. Stuart, and D.K.Y. Wong, Signal generation at an electrochemical immunosensor via the direct oxidation of an electroactive label. Electroanalysis 18, 237-246 (2006). 

S.M. Wilson, Electrochemical immunosensors for the simultaneous detection of two tumor markers. Anal. Chem. 77, 1496-1502 (2005). 

Y.V. Plekhanova, A.N. Reshetilov, E.V. Yazynina, A.V. Zherdev, and B.B. Dzantiev, A new assay format for electrochemical immunosensors polyelectrolyte-based separation on membrane carriers combined with detection of peroxidase activity by pH-sensitive field-effect transistor. Biosens. Bioelectron. 19, 109-114(2003). 

M. Dijksma, B. Kamp, J.C. Hoogvliet, and W.P. van Bennekom, Development of an electrochemical immunosensor for direct detection of interferon- at the attomolar level. Anal. Chem. 73, 901-907 (2001). 

A.F. Chetcuti, D.K.Y. Wong, and M.C. Stuart, An indirect perfluorosulfonated ionomer-coated electrochemical immunosensor for the detection of the protein human chorionic gonadotrophin. Anal. Chem. 71, 4088-4094 (1999). 

J. Wang, B. Tian, and K.R. Rogers, Thick-film electrochemical immunosensor based on stripping poten-tiometric detection of a metal ion label. Anal. Chem. 70, 1682-1685 (1998). 

Liu et al. [140] have also used this interface for an electrochemical immunosensor for small molecules (Figure 1.26). In this sensor, one end of the molecular wire is attached to ferrocene dimethylamine with a covalent link formed between one of the amine group son the ferrocene and the carboxyl group on the wire. To the other amine is attached the antibody-binding epitope for the antibody, in this proof-of-concept study the epitope is biotin. Electron transfer can be readily achieved to the ferrocene molecule but upon antibody binding to this interface, the electrochemical signal is dramatically reduced. 

Electrochemical immunosensors are a powerful tool for the analysis of antibacterials in food and different configurations have been presented during recent years. For example, an amperometric immunosensor was reported by Wu et al. [182], for penicillin quantification in milk, with a linear range from 0.25 to 3 ng/ml and a limit of detection of 0.3 pg/L [182]. Other types of transduction have been also explored, like a label-free impedimetric flow injection immunosensor for the detection of penicillin G. 

Electrochemical immunosensors are the most numerous of immunosensors. Their suitability for use in flow systems is limited by the two factors commented on above in dealing with fibre optic-based sensors, viz. the need for an incubation period and exceedingly long response times. 

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