Electrochemical Genosensing Based on Graphite-Epoxy Composite

4 Electrochemical Genosensing Based on Graphite-Epoxy Composite 

Adsorption is an easy way to attach nucleic acids to solid surfaces, since no reagents or modified-DNA are required, as shown in Fig. 3.3. These features have promoted extensive use of adsorption as immobilization methodology in genetic analysis. The mainly claimed disadvantages of adsorption with respect to covalent immobilization are (i) nucleic acids may be readily desorbed from the substrate and (ii) base moieties may be unavailable for hybridization if they are bonded to the substrate in multiple sites [76]. However, the electrochemical detection strategy based on the intrinsic oxidation of DNA requires the DNA to be adsorbed in close contact with the electrochemical substrate by multisite attachment, as schematically shown in Fig. 3.4. This multisite attachment of DNA can be thus detrimental for its hybridization but is crucial for the detection based on its oxidation signals. The common method for the multisite physical adsorption of DNA on carbonaceous-based materials can be classified into dry or wet adsorptions. 

Dry adsorption relies on leaving DNA to dry on the carbonaceous surface. It can be assisted by light treatment (except UV that is able 

The irreversible behavior of the dry adsorbed DNA layer has been previously reported on glassy carbon electrodes [77]. DNA can be tightly and irreversibly immobilized on GEC by both dry and wet adsorption procedures under static conditions [78]. The dual nature 

Moreover, by easily controlling the concentration of the DNA solution being dried on GEC platform, a thick or a thin layer of DNA can be formed on the GEC surface by dry adsorption [36]. Depending on the application of the DNA-modified substrate, a thick or thin DNA layer would be necessary. If a stringency control of non-specific 

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Electrochemical genosensing of food pathogens based on graphite-epoxy composite... 

M.I. Pividori and S Alegret, Electrochemical genosensing of food pathogens based on graphite epoxy-composite. In S. Alegret and A. Merkogi (Eds.), Comprehensive Analytical Chemistry, Vol. 49, Elsevier, 2007, pp. 437-464. 

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