Electrochemical biosensors techniques

Electrochemical biosensors combine die analytical power of electrochemical techniques with the specificity of biological recognition processes. The aim is to... 

Electrochemical biosensors are the most common especially when the biological component is an enzyme. Many enzyme reactions involve electroactive species being either consumed or generated and can be monitored by ampero-metric, potentiometric or conductimetric techniques, although the latter are the least developed and will not be discussed further. 

Our research group is working on the development of electrochemical biosensors for the detection of microcystin and anatoxin-a(s), based on the inhibition of protein phosphatase and acetylcholinesterase, respectively. These enzyme biosensors represent useful bioanalytical tools, suitable to be used as screening techniques for the preliminary yes/no detection of the toxicity of a sample. Additionally, due to the versatility of the electrochemical approach, the strategy can be applied to the detection of other cyanobacterial toxins. 

Magnetic AC atomic force microscopy (MAC Mode AFM) has proved to be a powerful surface analysis technique to investigate the interfacial and conformational properties of biological samples softly bound to the electrode surface and can be used as an important tool to characterize DNA-electrochemical biosensor surfaces [25,27],... 

Zhang S, Wright G, Yang Y. Materials and techniques for electrochemical biosensor design and construction. Biosensors Bioelectronics 2000, 15, 273-282. 

The use of DNA-electrochemical biosensors for the understanding of DNA interactions with molecules or ions exploits the use of voltammetric techniques for in situ generation of reactive intermediates and is a complementary tool for the study of biomolecular interaction mechanisms. 

In another study also, electrochemical impedance technique has been shown to be a useful method for a DNA biosensor using a multinuclear nickel(II) salicylaldimine metallodendrimer platform [164], Both the preparation of the dendrimer-modified GCE surface and the immobilization of DNA have been effectively done by simple drop-coating procedures. The metallodendrimer is electroactive exhibiting two redox couples in phosphate buffer solution. The impedance study demonstrated that the DNA biosensor responded well to 5 nM of target DNA by displaying a decrease in charge transfer resistance in phosphate buffer solution and increase in charge transfer resistance in the presence of the [Fe(CN)6]3/4" redox probe. 

Electrochemical biosensors have some advantages over other analytical transducing systems, such as the possibility to operate in turbid media, comparable instrumental sensitivity, and possibility of miniaturization. As a consequence of miniaturization, small sample volume can be required. Modern electroanalytical techniques (i.e., square wave voltammetry, chronopotentiometry, chronoamperometry, differential pulse voltammetry) have very low detection limit (1(T7-10 9 M). In-situ or on-line measurements are both allowed. Furthermore, the equipments required for electrochemical analysis are simple and cheap when compared with most other analytical techniques (2). Basically electrochemical biosensor can be based on amperometric and potentiometric transducers, even if some examples of conductimetric as well as impedimetric biosensor are reported in literature (3-5). 

Electrochemical detection has been regarded as particularly appropriate strategy for microfluidic chip systems. Electrochemical biosensors in microfluidic chips enable high sensitivity, low detection limits, reusability, and long-term stability. And the detection mechanism and instmmentation for realization are simple and cost-effective. These valuable features have made electrochemical devices receive considerable attention [20,94,95]. The electrochemical detectors are commercially available for a variety of analyses [96]. The review written by Wang summarized the principles of electrochemical biosensors, important issues, and the state-of-the-art [97]. Lad et al. described recent developments in detecting creatinine by using electrochemical techniques [98]. 

Chemistry (lUPAC) titled "Classification and Nomenclature of Elec-troanal)d icar Techniques" [1], "Recommended Terms, Symbols, and Definitions for Electroanal Aical Chemistry" [2], and "Recommended Terms, Symbols, and Definitions for Electroanal d ical Chemistry (Recommendations 1985)" [3] and in Compendium of Analytical Nomenclature The Orange Book [4]. Some special articles characterize electrochemical sensors [5]. A special lUPAC technical report, "Electrochemical Biosensors Recommended Definitions and Classification" [6], deals with techniques and terms of electrochemical biosensors. 

Electrochemical DNA biosensor techniques for the detection of microbiological and inherited diseases devoted to clinical analysis are presented dealing with past and novel developments in this chapter. For this purpose particular emphasis will be given to the most important approaches for electrochemical genosensing. 

---