Aptasensors protein-aptamer interactions

In its simplest, QCM, format, protein-aptamer interactions were analyzed by Liss et al. (2002). They compared the interaction of IgE with DNA aptamer as well as with anti-IgE antibodies. Although the detection limit was similar in the two cases, the advantage of the aptasensor was its possibility of surface regeneration, which was impossible for an antigen-based biosensor. However, recently it has been shown that immobilization of anti-IgE on the dendrimer surface also allows us to regenerate an immunosensor (Svobodova et al., 2006). The QCM method was recently compared with the electrochemical biosensor assay of thrombin detection (Hianik et al., 2005, 2007). It has been shown that the sensitivity of thrombin detection was similar for the two methods. Mascini and co-workers showed that similar results in sensitivity and selectivity in the detection of Tat peptide with RNA aptamer can be obtained by the QCM and SPR methods (Tombelli et al., 2005b). 

These aptasensors are based on the use of a redox probe such as methylene blue (MB) that undergoes an oxidation and reduction due to the electron transfer from an electrode surface to a probe. These redox probes are noncovalently bound to aptamers and intercalate or interact with aptamers mainly by electrostatic interactions. For example, MB, positively charged, interacts with negatively charged proteins or other negatively charged analytes. When... 

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