Chronopotentiometric detection

Co(phen) +/2+, Fe(phen)r/3+. Co(bpy) +/2+, Fe(bpy>r/3+ and Os(bpy)2+/3+ (where phen = 1,10-phenanthroline and bpy = 2,2 -bipyri-dyl). The binding was interpreted in terms of the interplay of electrostatic interactions of the metal coordination complexes with the charged sugar-phosphate backbone and the intercalative, hydrophobic, interactions within the DNA helix, i.e., the stacked base-pairs. Chronopotentiometric detection of the Co(bpy)3+ indicator was used [102] to monitor the hybridization onto a screen-printed carbon electrode of short DNA sequences from E. coli pathogen in environmental water samples. The couple Co(bpy) 5+/2+ was also used to evaluate the adsorption of DNA on gold electrodes [103-104]. 

There have been only very limited studies in literature on the exploitation of dendrimers in electrochemical DNA biosensors. The earliest report was by Wang et al on the chronopotentiometric detection of a 27-mer ss-DNA oligonucleotide of 2-layer and 4-layer dendrimers by adsorptive accumulation on carbon paste electrodes. The detection limits were found to be 3 and 12 pM for the 2- and 4- layers nucleic dendrimers respectively [159],... 

Voltammetric and chronopotentiometric detection modes are mostly used [20]. Together with them, electrochemical impedance spectroscopy (EIS) becomes to be popular at DNA-based biosensors [13]. According to electrochemi-cally active species which responses are evaluated at the detection of damage to DNA, the experimental techniques can be classified as follows [1] ... 

An electrochemical biosensor for the specific detection of short DNA sequences from the Escherichia coli E. coli) pathogen was suggested by Wang et al. The biosensor relied on the immobilization of the 25-mer oligonucleotide probe from the E. coli lacZ gene onto a screen-printed carbon electrode (SPCE). The hybridization event was monitored via chronopotentiometric detection of the Co(bpy)3 indicator. The biosensor detected 300 and 50 ng mL of E. coli DNA target with 20 and 30 min of hybridization time, respectively. Untreated environmental water samples were also used in order to present the applicability of the biosensor. 

FIGURE 6-14 DNA hybridization biosensors detection of DNA sequences from the E. coli pathogen. Chronopotentiometric response of the redox indicator upon increasing the target concentration in 1.0 pg/ml steps (a-c), in connection with a 2 min hybridization time. (Reproduced with permission from reference 46.)... 

J. Wang, X. Cai, G. Rivas, H. Shiraishi and N. Dontha, Nucleic-acid immobilization, recognition and detection at chronopotentiometric DNA chips, Biosens. Bioelectron., 12 (1997) 587-599. 

Palecek et al. [64] and Masarik et al. [65] detected a G-T mismatch at CPE and HMDE using chronopotentiometric stripping analysis (CSA) and squarewave voltammetry (SWV) in the presence of MutS. Cho et al. [66] found that the binding affinity of MutS for... 

Intercalator hybridization labels are complex molecules that have a planar aromatic group. Several methods for indicator-based electrochemical sequence specific to DNA detection have been reported. Wang et al. [41] described the hybridization detection of short DNA sequences related to HIV virus genome due to the chronopotentiometric transduction of Co(phen) as an hybridization label. Electrochemiluminescense assays have also been reported by Carter etal. [42] for specific DNA sequence detection. 

In PNA the entire sugar-phosphate is replaced by (Af-(2-amino-ethyl) glycine units. In contrast to DNA and RNA (with negatively charged backbones), PNA has an electrically neutral backbone. Electrochemical responses of PNA were similar to DNA and RNA (i.e. A, C and G were reduced on mercury electrodes G producing an anodic CV peak due to oxidation of the G reduction product and A and G were oxidized on carbon electrodes) [247]. Peak potentials of ssPNA at the HMDE were shifted to negative values as compared with ssDNA. Differences in backbones of PNA and DNA were manifested by the different adsorption behavior of these two compounds, as detected by a.c. impedance [108] on mercury (Fig. 3), and by chronopotentiometric measurements on carbon electrodes [129]. 

Large differences between the interfacial properties of ds and ssDNAs observed earlier by capacitance measurements [10, 37] suggested that a.c. impedance measurements could be used to detect DNA hybridization on electrodes [433, 434] (Sect. 12.8.). A three-component ODN system on a gold electrode (involving avidin-biotin interactions) was used to detect specific DNA sequences by means of faradaic impedance spectroscopy [435]. Impedance spectroscopy does not seem, however, to be the most convenient method for the DNA biosensor faster and simpler voltam-metric or chronopotentiometric methods will probably be more convenient. Gon-ductivity of the perfect DNA, contrasting with a loss of conductivity in duplexes with mismatched bases, may be of use in... 

Potentiometric stripping analysis (PSA) and chronopotentiometric stripping analysis (CPS) are an alternative techniques that may be used for the determination of metals such as Bi, Cd, Cu, Pb, Sn. Tl, and Zn in water samples [67]. With microprocessor controlled equipment, limits of detection are in the sub-pg/L range. The main advantage of PSA and CPS is that atmospheric oxygen dissolved in an aqueous sample does not have to be removed and that in many cases, in-... 

Xu, Y. and E. Bakker. 2008. Ion channel mimetic chronopotentiometric polymeric membrane ion sensor for surface-confined protein detection. Langmuir 25 568-573. 

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