Dendrimers, aptamer immobilization

Figure 5.2 SPR sensor response as a fnnction of thrombin concentration for different types of aptamer immobilization and different types of aptamer APTA immobilized on a (1) streptavidin layer (2) avidin (3) dendrimers covered by avidin (4) SH-APTA. For comparison, nonspecific interaction of HSA with a sensor snrface created by APTA immobilized on a streptavidin layer is shown (cnrve 5). The composition of aptamers was as follows APTA 3 -biotin-GGG TTT TCA CTT TTG TGG GTT GGT GTG GTT GG-5, SH-APTA SH-(CH2)e-GGT TGG TGT GGT TGG-5. Results represent meaniS.D. obtained from three independent experiments. [Adapted from Ostatnd et al. (2008), with permission of Springer.]...

Fig. 33.2. Schematic picture of the methods of immobilization of the aptamers (A) chemisorption. Biotinylated aptamer is immobilized on a surface covered by (B) avidin, (C) neutravidin and (D) avidin on a surface of poly(amidoamine) dendrimers (PAMAM). (E) Aptamer is immobilized on carbon nanotubes activated by Tween 20 (it is partially adapted from Ref. [39] with permission of American Chemical Society).

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). 

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