Hybrid Biosensors

Monitoring of specific proteins eluted from chromatographic columns was demonstrated using the ET as a direct online monitor for purification of proteins/enzymes. As an example, LDH was recovered from a solution by affinity binding of N6-(6-aminohexyl)-AMP-Sepharose gel, and the signal from the ET was used to regulate the addition of the AMP-Sepharose suspension to the LDH solution [26,27]. 

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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.)... 

F. Amarita, C. Rodriguez Fernandez and F. Alkorta, Hybrid biosensors to estimate lactose in milk, Anal. Chim. Acta, 349(1-3) (1997) 153-158. 

Figure 6.16 Steps involved in the detection of a specific DNA sequence using an electrochemical DNA hybridization biosensor. (Reproduced with permission from Ref. 71.)...

Electrochemical devices have proven very useful for sequence-specific biosensing of DNA. Electrochemical detection of DNA hybridization usually involves monitoring a current response under controlled potential conditions. The hybridization event is commonly detected via the increased current signal of a redox indicator (that recognizes the DNA duplex) or from other hybridization-induced changes in electrochemical parameters (e.g., conductivity or capacitance). Modern electrical DNA hybridization biosensors and bioassays offer remarkable sensitivity, compatibility with modern microfabrication technologies, inherent miniaturization, low cost (disposability), minimal power requirements, and independence of sample turbidity or optical pathway. Such devices are thus extremely attractive for obtaining the sequence-specific information in a simpler, faster, and cheaper manner, compared to traditional hybridization assays. 

Electrochemical DNA biosensors are based on the use of nucleic acids or analogues as biorecognition element and electrochemical techniques for the transduction of the physical chemical signal. Two aspects are essential in the development of hybridization biosensors, sensitivity and selectivity. Traditional methods for detecting the hybridization event are too slow and require special preparation. Therefore, there is an enormous interest in developing new hybridization biosensors, and the electrochemical represent a very good alternative [108]. 

An electrochemical DNA hybridization biosensor basically consists of an electrode modified with a single stranded DNA called probe [109]. Usually the probes are short oligonucleotides (or analogues such as peptide nucleic acids). The first and most critical step in the preparation of an electrochemical DNA biosensor is the immobilization of the probe sequence on the electrode. The second step is the hybrid formation under selected conditions of pH, ionic strength and temperature. The next step involves the detection of the double helix... 

Fig. 12 a Construction of the hybrid biosensor and fluorescence sensing for the doubly phosphorylated peptide, b Structure of the chemosensor imit on the hybrid biosensor, c Amino acid sequences of the WW domain and its mutant... 

J, J, Gooding, Electrochemical DNA hybridization biosensors. Electroanalysis 14[17], 1149-1156 C2002). 

J. Wang, G. Rivas, and X. Cai, Screen printed electrochemical hybridization biosensor for the detection of DNA sequences from Escherichia coli pathogen. Electroanalysis 9(5], 395-398 (1997]. 

M. Diaz-Gonzalez, A. de la Escosura-Muniz, M. B. Gonzalez-Garcia, and A. Costa-Garcia, DNA hybridization biosensors using polylysine modified SPCEs, Biosens. Bioelectron. 23(9), 1340-1346 (2008). 

J. H. Chen, J. Zhang, L. Y. Huang, X. H. Lin, and G. N. Chen, Hybridization biosensor using 2-nitroacridone as electrochemical indicator for detection of short DNA species of Chronic Myelogenous Leukemia, Biosens. Bioeiect. 24(3), 349-355 (2008). 

The nucleic acid recognition part selectively detects a specific gene sequence of DNA. A DNA hybridization biosensor uses a DNA strand of known sequence as a probe of a target DNA sample. 

Label-based electrochemical nucleic acid hybridization biosensors work on the principle of the following groups ... 

L. S. Elicia Wong, F. J. Mearns, and J.). Gooding, Further development of an electrochemical DNA hybridization biosensor based on long-range electron transfer. Sens. Actuators. B Chem. 111-112,515-521 (2005). 

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