Aptamers - future tools for diagnostics and therapy

The high target specificity and affinity make aptamers attractive tools for analytical, diagnostic or therapeutic purposes. aptamers are also used as research tools to study protein functions and interactions as well as molecular mechanisms of diseases. Nucleic acid aptamers are selected from an oligonucleotide library (10(15) sequences) by a selection scheme based on in vitro evolution principles (SELEX). Since the introduction of the aptamer technology in 1990, the great interest in aptamers is reflected by the growing number of publications and patent applications. Aptamers have been selected to various targets and more than 1100 aptamer sequences, mostly RNA, are found in data bases. One of the few disadvantages of aptamers is the instability of the RNA molecule. Several approaches to solve the problem have been presented. For instance, by introducing modified bases the in vivo half-life was increased from minutes to hours. other means of stabilization is the addition of sugars and by microencapsulation. The majority of the patents and publications on aptamers concern diagnostic approaches. There are also many publications, which describe the isolation and medical effects of aptamers directed to critical targets in diseases. A few of these aptamers are evaluated in clinical trials.