Enzyme-base amplification, electrochemical

He, Y, Zeng, K., Zhang, X. et al. (2010) Electrochemistry communications ultrasensitive electrochemical detection of nucleic acid based on the isothermal strand-displacement polymerase reaction and enzyme dual amplification. Electrochem. Commuru, 12 (7), 985-988. 

Electrochemical biosensors have been divided into two basic types enzyme-based sensor and electrochemical probe-based sensor. Alkaline phosphatase (ALP) and horse radish peroxidase (HRP) have been often employed for enzyme-based biosensors using p-nitrophenyl phosphate (PNP), a-naphtyl phosphate, 3-3, 5,5 -tetramethylbenzidine (TMB) and 2,2 -azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) as substrates of electrochemically active species, and ferrocene (Fc) and methylene blue as the electrochemical mediators. In general, enzymatic amplification of electrochemical signals enables highly sensitive detection of analytes. On the other hand, a direct detection of analytes by using electrochemical probes allows a more rapid time-response onto the detector surface and needs no enzymatic reaction. Based on the reason, a direct detection of analytes by using electrochemical probes has been... 

Enzyme DNA hybridization assays with electrochemical detection can offer enhanced sensitivity and reduced instrumentation costs in comparison with their optical counterparts. Efforts to prevent non-specific binding of the codissolved enzyme and to avoid fouling problems by selecting conditions suitable to amplify the electrode response have been reported by Heller and co-workers [107]. A disposable electrochemical sensor based on an ion-exchange film-coated screen-printed electrode was described by Limoges and co-workers for an enzyme nucleic acid hybridization assay using alkaline phosphatase [108] or horseradish peroxidase [109]. In another methodology to improve sensitivity, a carbon paste electrode with an immobilized nucleotide on the electrode surface and methylene blue as hybridization indicator was coupled, by Mascini and co-workers [110], with PGR amplification of DNA extracted from human blood for the electrochemical detection of virus. 

Numerous electrochemical platforms have been developed for DNA detection, including direct electrochemistry of the DNA bases [5], electrochemistry of different polymer-modified screen-printed chips [6], electrochemistry of DNA-specific redox indicator molecules or enzymes [7,8], electrochemistry of signal amplification with nanoparticles (NPs) such as gold, silver or magnetic particles [9,10], and dsDNA r-stacked mediated charge transport chemistry [4, 7,11,12]. 

Wang, C., Lin, M Liu, Y. and Lei, H. (2011) Electrochim. Acta, 56,1988-1994. Lin, M., Liu, Y, Sun, Z. et al. (2012) Electrochemical immunoassay of benzo[a]pyrene based on dual amplification strategy of electron-accelerated Fe304/polyaniline platform and multi-enzyme-fimctionalized carbon sphere label. Anal. Chim. Acta, 722, 100-106. 

These devices are based on the measurement of either electrochemical potential or faradaic current associated with redox reactions at an electrode. They are particularly suitable for enzyme-substrate receptor systems by virtue of the ionic products often produced in such reactions. The sensing membranes of the ion-selective electrodes previously described have been combined with semiconductor devices for miniaturization, low-impedance output, signal amplification, and capability of on-chip processing. The ion-sensitive field effect transistor (ISFET) is based on replacement of the conventional transistor gate with the ion-... 

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