DNA modified glassy carbon electrode

The ssDNA was prepared by treating a sample of calf thymus DNA of approximately 4 mg of dsDNA with 0.5 mL of 60% pure perchloric acid after dissolution, 0.5 mL of 9 M NaOH were immediately added to neutralize the solution followed by 9 mL of pH 4.5 acetate buffer. The DNA-modified glassy carbon electrode was prepared by covering a glassy carbon electrode with 3 mg of dsDNA dissolved in 80 jjlL of pH 4.5 acetate buffer and leaving the electrode to dry. The DNA layer was 0.5 mm thick and... 

Fig. 3.8. Differential pulse voltammograms of I mM guanosine 5 -monophosphate in 0.2 M acetate buffer (a) Bare glassy carbon electrode 1 - s.e. 2, 3, 4 - first, second and third scans in the guanosine solution 5-IOth scan 6-20th scan (b) DNA-modified glassy carbon electrode I - s.e. 2. 3. 4 - first, second and third scans in the guanosine solution. Pulse amplitude 50 mV. pulse width 70 ms. scan rate 5 mV s. s.e.=supporting electrolyte.

In the case of adenosine 5 -monophosphate, oxidation at a bare glassy carbon electrode leads to the rapid formation of products that adsorb irreversibly on the electrode surface and consequently the peaks diminish on successive scans (see Fig. 3.9, curves 2, 3, 4). On the contrary, the current obtained when using the DNA-modified glassy carbon electrode (Fig. 3.9, curve 6), is five times higher and there are no signs of electrode blocking by adsorption. 

The results obtained enable us to conclude that in the DNA-modified glassy carbon electrode, although the groups that undergo electrochemical... 

The possibility of reversible electron transfer within the modified DNA film was tested by carrying out an electrochemical study [85] of the redox couple Fe(lll)/Fe(Il) which has reasonably fast electrode kinetics, and which are dependent on electrode material. The oxidation of Fe(CN)g in 0.4 M K2S04 aqueous solution contacting the DNA-modified glassy carbon electrode showed virtually the same reaction rate as when using the bare glassy carbon electrode, Fig. 3.10, and the results were comparable to... 

Oliveira-Brett, A.M., Serrano, S.H.P., Macedo, T.A., Raimundo, D., Marques, M.H., LaScalea, M.A. Electrochemical determination of carboplatin in serum using a DNA-modified glassy carbon electrode. Electroanalysis 8, 992-995 (1996)... 

Fig. 2 Working procedure diagram for the automatization of measurement using the DNA-modified glassy carbon electrode (GCE)...

Blaskova M, Hajkova A, Vyskocil V (2015) Voltammetric determination of anthracene using a DNA-modified glassy carbon electrode. Chem Listy 109(3) 235-240... 

Figure 3.24 Schematic representation of the analytical protocol (A) Capture of the ALP-loaded CNT tags to streptavidin-modified magnetic beads by a sandwich DNA hybridization (a) or Ab-Ag-Ab interaction (b). (B) Enzymatic reaction. (C) Electrochemical detection of the product of the enzymatic reaction at the CNT-modified glassy carbon electrode MB, Magnetic beads P, DNA probe 1 T, DNA target P2, DNA probe 2 Abl, first antibody Ag, antigen Ab2, secondary...

Immobilization of the DNA onto polymer modified surface can be realized by electrodeposition, which is a well-known method [25]. Application of positive potential in this process can enhance the DNA immobilization as well as the stability of immobilized DNA. Diaz-Gonzalez etal. [26] studied the DNA immobilization onto a polylysine-modified electrode at different potentials. The best results were obtained using a potential of-1-0.5 V for 120 seconds. DNA was also electrodeposited onto a poly(p-aminobenzensulfonic acid)-modified glassy carbon electrode (GCE) at -fl.5 V for 30 minutes [27] or onto overoxidized Ppy-modified electrode at -1-1.8 V for 30 minutes [28]. 

Gutierrez, F.A., Rubianes, M.D., and Rivas, G.A. (2013) Adsorption and electrooxidation of DNA at glassy carbon electrodes modified with multiwall carbon nanotubes dispersed in glucose oxidase. Electroanalysis, 25, 1135—1142. 

Wang, J., Kawde, A.-N. and Musameh, M. (2003) Carbon-nanotube-modified glassy carbon electrodes for amplified label-free electrochemical detection of DNA... 

Zhang, C., Xu, S., Zhang, X., Huang, D., Li, R., Zhao, S., Wang, B., 2014a. Electrochemical detection of specific DNA sequences related to bladder cancer on CdTe quantum dots modified glassy carbon electrode. Journal of Electroanalytical Chemistry 735,115—122. 

Another interesting example on the detection of HBV was given by Niu et al.. [79]. They developed a novel and sensitive eleetrochemical DNA biosensor for the detection of DNA hybridization. Copper(II) complex of Luteolin CsoHigCuOn (CUL2) was used as an electroaetive indieator and the biosensor was fabricated with silver nanoparticles and multi-walled earbon nanotubes (Ag/MWCNTs) modified glassy carbon electrode (GCE). The... 

Another important electroanalytieal application of modified electrodes is DNA detection [34-40]. Zhang et al. [39] produced an electrochemical DNA sensor based on silver nanoparticles/poly(trans-3-(3-pyridyl) aciylic acid) (PPAA)/multiwalled carbon nanotubes with carboxyl groups (MWCNTs-COOH) modified glassy carbon electrode (GCE). The polymer film was electropolymerized onto MWCNTs-COOH modified electrode by cyclic voltammetry, and then silver nanoparticles were electrodeposited on the surface of PPAA/MWCNTs-COOH composite film. The novel electrochemical detection method of DNA hybridization-based modified electrode has been developed with high sensitivity and selectivity. Furthermore the results of the experiment indicated that the DNA sensor is of excellent reusability. 

G. Cheng, J. Zhao, Y. Tu, P. He, and Y. Fang, A sensitive DNA electrochemical biosensor based on magnetite with a glassy carbon electrode modified by multi-walled carbon nanotubes in polypyrrole. Anal. Chim. Acta 533, 11-16 (2005). 

Some similar features were observed concerning the adsorption and electrochemical oxidation of DNA on glassy carbon and tin oxide electrodes [68]. Differential pulse voltammograms were recorded in buffer solution without DNA after adsorption of DNA onto the electrode surface during a predetermined time at a fixed potential suggesting the possibility of using adsorption to preconcentrate DNA on solid electrode surfaces and use this DNA-modified electrode for analytical purposes. 

If we consider Figs. 3.8 and 3.9, where the results for the oxidation of guanosine and adenosine 5 -monophosphates at a bare glassy carbon electrode and at a DNA-modified electrode are presented, several facts are worth mentioning when comparing voltammograms at both electrodes. 

Due to their simplicity of construction, ease of modification, electrical methods of detection, fast response time and the fact that they are the principal structural component of all biomembranes, conventional bilayer lipid membrane (BLM) arises as an ideal system for biosensor technology [88] and they have been studied regarding the possibility of developing DNA biosensors consisting of a glassy carbon electrode-modified by a BLM with incorporated ssDNA [89]. 

DNA adsorbed on a glassy carbon electrode was also used as an effective electron promoter enabling electron transfer via hopping conduction through electrode/base pair/cytochrome c by Ikeda et al. [128]. Gold electrodes modified with short oligonucleotides inunohilized via thiol chemisorption were described hy Lisdat et al. [129] to study the promotion of electron transfer to cytochrome c. 

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