Detection electrochemical biosensor

Recent attempts have concentrated on electrochemical biosensors for the determination of 02 due to their direct, real-time measurements and capability for in vivo detection. Electrochemical biosensors for the determination of 02 based on its reduction by cyt c as a biological recognition element were reported using the reoxidation of cyt c on an electrode surface (Prieto-Simon et al., 2008 Wang et al., 2014 Shipovskov et al., 2004 Fujita et al., 2009). However, cyt c is not a specific enzyme for the reduction of 0 i. Indeed, the tissue/cell extract contains cyt c oxidases, peroxidases, and oxidants including H2O2 and ONOO that can also reoxidize the reduced cyt c. Consequently, the cyt c-based methods are not suitable for assessment of 02 levels in biological systems. 

MWNTs favored the detection of insecticide from 1.5 to 80 nM with a detection limit of InM at an inhibition of 10% (Fig. 2.7). Bucur et al. [58] employed two kinds of AChE, wild type Drosophila melanogaster and a mutant E69W, for the pesticide detection using flow injection analysis. Mutant AChE showed lower detection limit (1 X 10-7 M) than the wild type (1 X 10 6 M) for omethoate. An amperometric FIA biosensor was reported by immobilizing OPH on aminopropyl control pore glass beads [27], The amperometric response of the biosensor was linear up to 120 and 140 pM for paraoxon and methyl-parathion, respectively, with a detection limit of 20 nM (for both the pesticides). Neufeld et al. [59] reported a sensitive, rapid, small, and inexpensive amperometric microflow injection electrochemical biosensor for the identification and quantification of dimethyl 2,2 -dichlorovinyl phosphate (DDVP) on the spot. The electrochemical cell was made up of a screen-printed electrode covered with an enzymatic membrane and combined with a flow cell and computer-controlled potentiostat. Potassium hexacyanoferrate (III) was used as mediator to generate very sharp, rapid, and reproducible electric signals. Other reports on pesticide biosensors could be found in review [17],... 

M. Ozsoz, A. Erdem, P. Kara, K. Kerman, and D. Ozkan, Electrochemical biosensor for the detection of interaction between arsenic trioxide and DNA based on guanine signal. Electroanal. 15, 613-619... 

Electrochemical biosensors based on detection of hydrogen peroxide at platinized electrodes were found to be more versatile allowing a decrease in detection limit down to 1 i,mol L 1 [109]. However, all biological liquids contain a variety of electrochemically easily oxidizable reductants, e.g. ascorbate, urate, bilirubin, catecholamines, etc., which are oxidized at similar potentials and dramatically affect biosensor selectivity producing parasitic anodic current [110]. 

CNTs offer an exciting possibility for developing ultrasensitive electrochemical biosensors because of their unique electrical properties and biocompatible nanostructures. Luong et al. have fabricated a glucose biosensor based on the immobilization of GOx on CNTs solubilized in 3-aminopropyltriethoxysilane (APTES). The as-prepared CNT-based biosensor using a carbon fiber has achieved a picoamperometric response current with the response time of less than 5 s and a detection limit of 5-10 pM [109], When Nation is used to solubilize CNTs and combine with platinum nanoparticles, it displays strong interactions with Pt nanoparticles to form a network that connects Pt nanoparticles to the electrode surface. The Pt-CNT nanohybrid-based glucose biosensor... 

J.H.T. Luong, S. Hrapovic, and D. Wang, Multiwall carbon nanotube (MWCNT) based electrochemical biosensors for mediatorless detection of putresdne. Electroanalysis 17, 47—53 (2005). 

Electrochemical biosensors are analytical devices in which an electrochemical device serves as a transduction element. They are of particular interest because of practical advantages, such as operation simplicity, low expense of fabrication, and suitability for real-time detection. Since the first proposal of the concept of an enzyme-based biosensor by Clark, Jr [1], significant progress in this field has been achieved with the inherited sensitivity and selectivity of enzymes for analytical purposes. 

Ivnitski, D., Abdel-Hamid, I., Atanasov, P., Wilkins, E., and Strieker, S. (2000). Application of electrochemical biosensors for detection of food pathogenic bacteria. Electroanalysis 12, 317-325. 

Ruan, C., Wang, H., and Li, Y. (2002a). A bienzyme electrochemical biosensor coupled with immunomagnetic separation for rapid detection of Escherichia coli 0157 H7 in food samples. Trans. ASAE 45,249-255. 

G. Palleschi, Extraction of enzyme inhibitors using a mixture of organic solvent and aqueous solution and their detection with electrochemical biosensors. The Eighth World Congress on Biosensors. P 3.7.64, Abstract Book. Granada, Spain, 2004. 

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. 

Results obtained with the electrochemical biosensor were compared to those obtained from the colorimetric PPI assay with the enzyme in solution and by HPLC (see Table 21.1 of Procedure 21 in CD accompanying this book). All real samples contained microcystin at levels detectable by the amperometric biosensor and the colorimetric PPI... 

Next, some typical examples will be presented of how a DNA-electrochemical biosensor is appropriate to investigate the DNA damage caused by different types of substances, such as the antioxidant agent quercetin (Scheme 20.1), an anticancer drug adriamycin (Scheme 20.2) and nitric oxide. In all cases, the dsDNA damage is detected by changes in the electrochemical behaviour of the immobilized dsDNA, specifically through modifications of the purinic base oxidation peak current [3,5,40]. 

S.R. Mikkelsen, Electrochemical biosensors for DNA sequence detection, Electroanalysis, 8 (1996) 15-19. 

G. Marrazza, G. Chiti, M. Mascini and M. Anichini, Detection of human apolipoprotein E genotypes by DNA electrochemical biosensor coupled with PCR, Clin. Chem., 46 (2000) 31-37. 

J. Wang, G. Rivas, C. Parrado, X. Cai and M.N. Flair, Electrochemical biosensor for detecting DNA sequences from the pathogenic protozoan Cryptosporidium parvum, Talanta, 44 (1997) 2003-2010. 

F. Azek, C. Grossiord, M. Joannes, B. Limoges and P. Brossier, Hybridization assay at a disposable electrochemical biosensor for the attomole detection of amplified human cytomegalovirus DNA, Anal. Biochem., 284 (2000) 107-113. 

Both the determinations reported here rely on the inhibition activity of OPs pesticides toward AChE combined with the detection of the AChE enzyme product choline at the surface of a mediator-modified screen-printed choline oxidase electrochemical biosensor. 

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