Aptamers compared with antibodies

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). 

DNA or RNA aptamers - the single stranded nucleic acids with high affinity to proteins or to other low and macromolecular compounds, which is comparable with that of antibodies. These special characteristics open new routes in biosensor assembling for further practical applications, such as detection of toxicants in food or environment. 

Aptamers—short functional oligonucleotides (or proteins in some cases) that recognize target antigen protein—can be used in an immunoassay platform. Compared with traditional antibodies, aptamers have many specific advantages... 

Stadtherr et al., 2005) detection of IgE in simple solution that provided detectability down to 100 pM IgE [corresponding to 5 fmol using a 50-tiL aliquot in the case of one immobilized aptamer sensor (Xu et al., 2005)], and use of fluorescent-labeled IgE aptamer in the run buffer in affinity CE that gave a detection limit of 46 pM IgE in simple solution but yielded detectable signals only for serum that was spiked with 5 nM IgE and not for native IgE in the serum (German et al., 1998). In the present work we achieved capture and detection of native IgE in human serum and found that dilution of the serum by at least 10 -fold allowed detection of native IgE with little interference from other serum proteins. This is comparable to detectability of a commercial antibody-based ELISA kit that offers 75 pM detection (Stadtherr et al., 2005). 

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