Aptamer technology

Another nucleic acid technology that has demonstrated utility in proteomics involves the use of aptamers and photoaptamers (Zichi et al., 2002). Aptamers (a word derived from the Latin aptus, meaning to fit) are oligonucleotides that selectively bind proteins. Jayasena (1999) prepared a comprehensive review of aptamer technology focusing on diagnostic utility. 

C. P. (2006). First-in-human experience of an antidote-controUed anticoagulant using RNA aptamer technology a phase la pharmacodynamic evaluation of a drug-antidote pair for the controlled regulation of factor IXa activity. Circulation 114, 2490-2497. 

Another class of compounds making nse of ODN stmc-tures are aptamers ohgonncleotide seqnences that have been identified (via in vitro selection) to bind to target proteins and biomolecules through a defined three-dimensional structure. Several aptamers have been shown to be effective as PPI inhibitors, and some have advanced to clinical use. For an overview of aptamer technology, the reader is directed to a recent review in the field. ... 

Kleimnan et al. 2008). In addition, synthetic siRNAs are also subject to degradation in vivo by nuclease activity. Besides side effects and instability, the efficient and specific delivery of the RNAi indncers to the target cell still requires optimization. Here we snmmarize the cnrrent statns of nncleic acid-based antiviral therapentics. The focns will be on antiviral strategies nsing antisense and RNAi technology. Additionally, antiviral ribozymes and aptamers will be discussed briefly, with a focus on recent studies. Gene therapy approaches and delivery systems are the subject of Chapter 11 of this book. 

As we will soon discover, microarray-based technologies have found utility in a number of fields. While DNA arrays are the most technically mature and have the broadest application portfolio, we have witnessed the ever-increasing generation of new kinds of probe arrays antibody, antigen, enzyme, aptamer, carbohydrate, tissue, cell, and small molecule microarrays. The list undoubtedly will continue to expand. We can also describe microarrays in terms of prognostic, diagnostic, and predictive roles. A few examples that examine these applications are provided. 

However, recombinant antibodies may be less stable and have lower binding affinities than monoclonal antibodies (Valle and Jendoubi, 2003). Therefore, in order to fully implement the microarray format, a host of diverse capture agents could be required in addition to antibodies. These include peptides, small molecules, aptamers, ribozymes, or other molecular recognition probes yet to be discovered. However, it is also xmderstandable because of the diverse nature of proteins that additional technologies besides microarrays will be used in proteomics research (Hanash, 2003). 

Despite being relatively new technology, aptamers have a tremendous potential and can be envisioned to rival antibodies and other traditional recognition elements for molecular detection and recognition, due to their inherent affinity, selectivity, and ease of synthesis. In addition, the combination of aptasensors with electrochemical detection methods has the added advantage of further cost reduction and miniaturization of such systems. 

The main difficulty with this technology is the possible interaction of target and/or ap tamer with the chip surface. The nature of this difficulty may be high unspecific interaction or high repulsion. For this reason, the most suitable sensor chip surface and optimal binding conditions must be determined for every target/aptamer combination. 

In this part we will describe recent achievements in the development of biosensors based on DNA/RNA aptamers. These biosensors are usually prepared by immobilization of aptamer onto a solid support by various methods using chemisorption (aptamer is modified by thiol group) or by avidin-biotin technology (aptamer is modified by biotin) or by covalent attachment of amino group-labeled aptamer to a surface of self-assembly monolayer of 11-mercaptoundecanoic acid (11-MUA). Apart from the method of aptamer immobilization, the biosensors differ in the signal generation. To date, most extensively studied were the biosensors based on optical methods (fluorescence, SPR) and acoustic sensors based mostly on thickness shear mode (TSM) method. However, recently several investigators reported electrochemical sensors based on enzyme-labeled aptamers, electrochemical indicators and impedance spectroscopy methods of detection. 

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