Aptamers, switches based

Wang, J. L., Wang, F. A., Dong, S. J. (2008). Methylene blue as an indicator for sensitive electrochemical detection of adenosine based on aptamer switch. J. Electronal. Chem. in press. 

Figure 19-17 also indicates that flat, aromatic molecules can be inserted between the flat, hydrogen-bonded nucleotide base pairs of DNA. We say that the flat molecule is intercalated between the base pairs. One of many analytical applications of aptamers utilizes a molecular light switch intercalated in the aptamer. 

Rodriguez, M. C., Kawde, A-N., Wang, J. (2005). Aptamer biosensor for label-free impedance spectroscopy detection of proteins based on recognition-induced switching of the surface charge. Chem Commun 34, 4267-4269. 

Wu, Z-S., Guo, M-M., Zhang, S-B., Chen, C-R., Jiang, J-H., Shen, G-L., Yu, R. Q. (2007). Reusable electrochemical sensing platform for highly sensitive detection of small molecules based on structure-switching signaling aptamers. Anal Chem 79,... 

Q. (2007). Reusable electrochemical sensing platform for highly sensitive detection of small molecules based on structure-switching signaling aptamers. Anal Chem 79, 2933-2939. 

The exciting properties of nucleic acids have opened new scenarios in the field of nanotechnology and sensor development. In particular, the dynamic properties of nucleic acids and the thermally indnced sequence-dependent separation of double-stranded DNA allow the utilization of nucleic acids with machinelike functions that can perform different motions or act as switches and motors (Beissenhirtz and Willner, 2006). The same principles have been applied for the development of aptamer-based machines, which can amplify the recognition event between the aptamer and the substrate through operation of the machine (Shlyahovsky et al., 2007). A scheme for the assay developed for cocaine is reported in Figure 8.10. 

Li, B. L., Wei, H., Dong, S. J. (2007a). Sensitive detection of protein by an aptamer-based label-free fluorescing molecular switch. Client Commun 13-15. 

Wang, J., Jiang, Y. X., Zhou, C. S., Fang, X. H. (2005). Aptamer-based ATP assay using a luminescent light switching complex. Anal Chem 77, 3542-3546. 

Aptamers have an even more diverse role in diagnostics. - Highly specific aptamers have been used as affinity probes in CE and proteomic microarrays. " - Aptamers have been incorporated into fluorescent switches and beacons. - They have been incorporated into chromatography and capillary electrochromatography " stationary phases. They have even been used as the sensing element of cantilever-based detectors." Clearly, the combination of high affinity and selectivity provided by aptamers can be applied to a wide range of analytical techniques. 

Recently, Xu s group reported the detection of ATP using the solution-based ECL with an ECL molecular switch [Ru(bpy)2dppz]. Different from the Ru(phen)3 +, the addition of DNA decreased the ECL intensity compared with that in the absence of DNA. ECL of [Ru(bpy)2dppz] + was negligible in aqueous solution, and increased ca. 1000 times when it intercalated into the nucleic acid structure. The presence of ATP can dramatically affect ECL of [Ru(bpy)2dppz] /ATP aptamer complex. As a result, a label-free, sensitive, and selective [Ru(bpy)2dppz] + ECL method for ATP detection was developed. 

Table 2.2. Aptamer-based biosensors based on the "switch-off" approach...

Figure 2.8. (a) The microfluidic electrochemical aptamer-based sensor chip, (b] The syringe pumps connected to a four-input, single-output multiplexed valve, (c) The detection mechanism of the switch on sensor. 

S. Zhang, J. Xia, and X. Li, Electrochemical biosensor for detection of adenosine based on structure-switching aptamer and amplification with reporter probe DNA modified Au nanoparticles. Anal Chem., 80, 8382-8388 [2008]. 

Cao s group in 2011 designed an ECL biosensor based on the construction of triplex DNA for the detection of adenosine which employs an aptamer as a molecular recognition element and quenches ECL of Ru(bpy)3 by ferrocene monocarboxylic acid (FcA) G ig. 6.5). In the presence of adenosine, the aptamer sequence (Ru-DNA-1) more likely forms the aptamer—adenosine complex with hairpin configuration and the switch of the DNA-1 occurs in conjunction with the... 

Another construction procedure of Fc-labeled structure-switching signaling aptamer as a sohd-state ECL sensing platform for detection of adenosine provided a promising method for aptamer-based small-molecule detection due to its simplicity, rapidity, low cost, and excellent response characteristics [155]. 

Zhu, Z. et al., Multiplexed detection of small analytes by structure-switching aptamer-based capillary electrophoresis. Analytical Chemistry, 2010 82(11) 4613-4620. 

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