Biosensors development

Oxidation of P-nicotinamide adenine dinucleotide (NADH) to NAD+ has attracted much interest from the viewpoint of its role in biosensors reactions. It has been reported that several quinone derivatives and polymerized redox dyes, such as phenoxazine and phenothiazine derivatives, possess catalytic activities for the oxidation of NADH and have been used for dehydrogenase biosensors development [1, 2]. Flavins (contain in chemical structure isoalloxazine ring) are the prosthetic groups responsible for NAD+/NADH conversion in the active sites of some dehydrogenase enzymes. Upon the electropolymerization of flavin derivatives, the effective catalysts of NAD+/NADH regeneration, which mimic the NADH-dehydrogenase activity, would be synthesized [3]. 

Sojka, B., Piunno, P. A. E., Wust, C. C., and Krull, U. J., Evaluating the quality of oligonucleotides that are immobilized on glass supports for biosensor development, Anal. Chim. Acta, 395, 273, 1999. 

The Array Biosensor developed at the Naval Research Laboratory (NRL) is an automated, portable detection device for simultaneous analysis of up to six samples for multiple analytes with the size of a shoebox (Figure 10) 42-43. 

The applications of nanoparticles in biosensors can be classified into two categories according to their functions (1) nanoparticle-modified transducers for bioanalytical applications and (2) biomolecule-nanoparticle conjugates as labels for biosensing and bioassays. We intend to review some of the major advances and milestones in biosensor development based upon nanoparticle labels and their roles in biosensors and bioassays for nucleic acids and proteins. Moreover, we focus on some of the key fundamental properties of certain nanoparticles that make them ideal for different biosensing applications. 

Some new developments are also proposed such as a system based on the use of electrochemically active bacteria in combination with a microbial fuel cell [34], giving good responses over 60 days, or a biosensor developed for fast... 

Fig. 18b.1. Electrochemical cells and representative cell configurations, (a) Schematic diagram of a cell-potentiostat system, (b) Typical laboratory cell with Hg-drop electrode and drop knocker, (c) Voltammetric cell as detector at the end of a high-performance liquid chromatographic column, (d) A two-electrode (graphite) chip cell for biosensor development, (e) Three-electrode chip cells on a ceramic substrate for bioanalytical work.

Topics discussed above are some basic principles and techniques in voltammetry. Voltammetry in the frequency domain where i-E response is obtained at different frequencies from a single experiment known as AC voltammetry or impedance spectroscopy is well established. The use of ultramicroelectrodes in scanning electrochemical microscopy to scan surface redox sites is becoming useful in nanoresearch. There have been extensive efforts made to modify electrodes with enzymes for biosensor development. Wherever an analyte undergoes a redox reaction, voltammetry can be used as the primary sensing technique. Microsensor design and development has recently received... 

Figure 1.26 Scheme of immuno-biosensor developed by Liu and Gooding, exploiting the size of proteins and the space that a protein takes up to block ion access to the redox probe. (Reproduced by permission of The Royal Society of Chemistry from [142].)... 

Biosensors based on microbial immobilization have also been used for food applications, e.g., the inexpensive and rapid high-throughput bacterial biosensor developed by Virolainen et al. for rapid detection of tetracyclines and their 4-epimer derivatives in poultry meat [188, 189]. 

The experimental data presented show that sNPS can be used as transducers, which are stable for a long time after the construction of an immune biosensor. The specific immune complex formed on the sNPS surface may be registered by measuring its photoluminescence or photoconductivity. Such immune biosensors can be applied for control of T2 mycotoxin. The biosensors developed are sensitive and simple and allows for rapid analysis and analysis in field conditions. This approach may be applied for detection of any biochemical substances which can form an immune complex. Further investigations should be directed towards studying the mechanism of the biochemical signal detection by the sNPS and characterization of all the steps of analysis. 

Heat is the most common product of biological reaction. Heat measurement can avoid the color and turbidity interferences that are the concerns in photometry. Measurements by a calorimeter are cumbersome, but thermistors are simple to use. However, selectivity and drift need to be overcome in biosensor development. Changes in the density and surface properties of the molecules during biological reactions can be detected by the surface acoustic wave propagation or piezoelectric crystal distortion. Both techniques operate over a wide temperature range. Piezoelectric technique provides fast response and stable output. However, mass loading in liquid is a limitation of this method. 

The possibilities of these approaches, considering the large numbers of potentially useful biochemical reactions, are enormous. It is expected that significant advances will occur in the field of biosensor development in the near future, especially when newer biotechnological processes and chemical modification approaches are adapted to sensor development. 

E. Akyilmaz and E. Dingkaya, An amperometric microbial biosensor development based on Candida tropicalis yeast cells for sensitive determination of ethanol, Biosens. Bioelectron., 20(7) (2005) 1263-1269. 

Table 23.7 presents an overview of SPCE-based sensors and biosensors developed before 2003 for the determination of pharmaceutical compounds. 

However, it should be mentioned that there is a flexible hand-held electrochemical instrument on the market, which can be programmed to be used in a variety of voltammetric/amperometric modes in the field [209]. Although the majority of biosensor applications described in this review were for single analyte detection, it is very likely that future directions will involve development of biosensor arrays for multi-analyte determinations. One example of this approach has been described in an earlier section, where five OPs could be monitored with an array of biosensors based on mutant forms of AChE from D. melanogaster [187]. This array has considerable potential for monitoring the quality of food, such as wheat and fruit. Developments and applications of biosensors in the area of food analysis are expected to grow as consumer demand for improved quality and safety increases. Another area where biosensor developments are likely to increase significantly is in the field of environmental analysis, particularly with respect to the defence of public... 

Such mediator-linked assays, even at the simplest original one enzyme level can seem an elegant solution for a biosensor. Nevertheless, optimisation of the reagents alone is not the complete solution. As discussed earlier, the reagents must be immobilised to interact with both analyte and transducer as a self contained system, before the biosensor label is attached. This prerequisite is far from trivial and is a major preoccupation in all branches of biosensor development. 

The immobilization of peroxidases can be classified in agreement with the support used for immobilization. In this way, three main types can be mentioned on organic, inorganic, and hybrid supports. Each of them displays their own characteristics that make them catalytically attractive and potentially applicable. Next, some examples and strategies are described. Additionally, peroxidases have been immobilized for their use in biosensors development with applications in diagnosis or electronics. These interesting and novel applications are covered in Chap. 6. 

Karymov, M. A., Kruchinin, A. A., Tarantov, Y. A., Balova, I. A., Remisova, L. A. and Vlasov, Y. G. (1995). Fixation of DNA Directly on Optical Wave-Guide Surfaces for Molecular Probe Biosensor Development. Sens. Actuators, B Chemical 29 324-327. 

Thus, bioprocess-related biosensor development today has to deal with new challenges in biochemical engineering. 

There are hundreds if not thousands of miniaturized biosensors published in literature today. Thus, a selection of only a few of them for a brief description is a difficult task. While the biosensors described here are exceptional examples of miniaturized systems, there are many others that would have deserved a description as well, if the space had been available. A selection has been made to give an overview of interesting biosensors such as DNA microarrays, biosensors coupled with capillary electrophoresis (CE), cantilever-based biosensors, electrochemical systems, optical biosensors, and visions of a p.TAS. The examples are described only briefly, for a complete understanding of the work published, the reader is advised to refer to the original publication. Hopefully, this overview gives a grasp of the interesting biosensors developed in the new miniature world. 

The basic requirement in biosensor development is ascribed to the successful attachment of the recognition material, a process governed by various interactions between the biological component and the sensor interface. Advanced immobilization technologies capable of depositing biologically active material onto or in close proximity of the transducer surface have been reported. In this context, the choice of a biocompatible electrode material is essential. The material surfaces (support) include almost all material tjrpes metals, ceramics, polymers, composites and carbon materials [8]. In most cases, when a native material does not meet all the requirements for... 

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