Biosensors aptasensors

New Frontiers in Nucieic Acid-Based Piezoeiectric Biosensors Aptasensors... 

We now have a new class of biosensors, aptasensors, which use aptamers as highly selective recognition elements. As receptor molecules, aptamers allow widespread applicability to a diverse array of target analytes due to their analyte-impartial synthetic generation process. Aptasensors realized on micro- and nanoscale platforms afford many potential advantages, such as miniaturized construction rapid, sensitive, and specific detection high throughput reduced... 

Keywords Clinical diagnostics Biowarfare agent detection Pharmaceutical analysis Environmental analysis Immunoassays DNA biosensor Aptasensor... 

Genosensors [deoxyribonucleic acid (DNA)-based biosensors], immunosensors, cytosensors, and aptamer-based biosensors (aptasensors) are types of affinity-based biosensors. 

Several electrical aptamer biosensors implemented the biocatalytic hydrolytic activities of thrombin, or the fact that proteins (e.g., thrombin) often include several binding sites for the formation of supramolecular complexes with different aptamers. The bioelectrocatalytic detection of thrombin by an electrical aptasensor was demonstrated by formation of an aptamer-thrombin complex on the electrode, followed by a thrombin-mediated hydrolysis of the nitroaniline-functionalized peptide, (22), yielding the redox-active product nitroaniline, (23), which was analyzed electrochemically76 (Fig. 12.20b). A further bioelectrocatalytic aptasensors configuration is depicted in Fig. 12.20c, where the multidentate formation of aptamer-protein supramolecular complexes was used to analyze thrombin.76 Thrombin includes two different binding sites for aptamers.77 One of the thrombin aptamers... 

Comparison of the developed aptasensor with other Tat detection methods is very difficult since most of the published papers on this subject deal with Tat-derived peptides and not with the full length protein. Anyway, the results demonstrated that the use of a biosensor with a specific aptamer as biorecognition element could be an interesting approach in the detection of proteins, which has been examined here considering a model system. 

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). 

In this review we described the most commonly used label-free aptasensor strategies. Although aptamers are one of the most promising systems for applications in biosensors, their potential applications using complex matrices as real samples remain the major challenges for point-of-care applications therefore, complementary strategies involving nanomaterials are a subject of intense study. 

We are presently in the early days of the emerging technology of using aptamers and nanomaterials to modify biosensors. So far, thrombin-binding aptamer has been the topic of numerous reports, but although many improvements are required in reproducibility and sensitivity, there is no doubt that a growing number of aptamers and, it is to be hoped, nanomaterial-based label-free aptasensors will soon be used for the diagnosis and therapeutic follow-up of diseases. 

The potential use of aptamers as receptors in biosensors and bioassays has been extensively reviewed [1-7] and also several books have appeared in the last years [8,9]. In this chapter, the current status of research in electrochemical aptasensors is considered. Attention is focused on label-free and labeled aptasensors, and the anal3Aical capabilities of these devices are discussed. 

Electrochemical biosensors based on DNA aptamers (aptasensors) are of growing interest due to their high sensitivity and selectivity. This is particularly due to unique properties of... 

Aptamer-based biosensors, also called aptasensor have gain a wide interest in the last years due to the advantages of aptamers compared to antibodies. Similar to antibodies, a variety of immobilization methods is available to bind aptamers to the sensor element. Aptasensors can be coupled to an electrochemical, optical or mass-sensitive transducer [13]. One of the successful examples for aptasensor was the detection of thrombin which was widely investigated [14]. Xiao et al. [15] have made an interesting development a redox compound (methylene blue) was inserted into the thrombin aptamer. When the target bound to the aptamer, the induced conformation change inhibited the electron transfer from the methylene blue to the electrode. This change could be detected amperometrically. 

Biosensors that employ aptamers as a recognition element are called aptasensors. Aptasensors will be more stable and well adapted to the conditions of real samples because of the specific properties of aptamers. Aptamers are single-stranded RNA or DNA molecules that bind to their target molecules with high specificity and affinity. Aptamers have been developed for different appHcations. Their use as biological recognition elements... 

Affinity biosensors, namely genosensors, immunosensors and aptasensors, can be suitably developed to quantify the amount of many biohazard agents in environment. The list of the species possibly detectable by one of these sensor systems is quite wide. It ranges from simple chemical species, e.g. heavy metal ions, to more complex pathogenic microorganisms. ... 

Hernandez EJ, Ozalp VC (2012) Graphene and other nanomaterial-based electrochemical aptasensors. Biosensors 2 1-14... 

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