Abstract
Aptamers and SELEX (systematic evolution of ligands by exponential enrichment) technology have gained increasing attention over the past 25 years. Despite their functional similarity to protein antibodies, oligonucleotide aptamers have many unique properties that are suitable for clinical applications and industrialization. Aptamers may be superior to antibodies in fields such as biomarker discovery, in vitro and in vivo diagnosis, precisely controlled drug release, and targeted therapy. However, aptamer commercialization has not occurred as quickly as expected, and few aptamer-based products have yet successfully entered clinical and industrial use. Thus, it is important to critically review some technical barriers of aptamer and SELEX technology per se that may impede aptamer development and application. To date, how to rapidly obtain aptamers with superior bioavailability over antibodies remains the key issue. In this review, we discuss different chemical and structural modification strategies aimed to enhance aptamer bioavailability. We also discuss improvements to SELEX process steps to shorten the selection period and improve the SELEX process success rate. Applications in which aptamers are particularly suited and perform differently or superior to antibodies are briefly introduced.
Highlights
In the past 25 years, aptamers and SELEX technology have gained great attention [1,2]
This review focuses instead on the applications in which aptamers perform differently or better than monoclonal antibodies
Aptamer and SELEX technology have brought a revolution to biomedical fields since their introduction in 1990
Summary
In the past 25 years, aptamers and SELEX (systematic evolution of ligands by exponential enrichment) technology have gained great attention [1,2]. The conventional SELEX technique and dozens of variations have been used successfully to develop aptamers against hundreds of targets, including synthetic peptides or purified proteins [18,19,20], aptamers developed through these types of SELEX techniques are not always effective for in vivo applications [21] This is because target molecule conformations during in vitro selection are usually different from their native conformations under in vivo physiological conditions, and conformational recognition is the most important parameter for aptamer binding to their cognate targets. The first impediment is that nucleic acid aptamers generated in vitro have different bioavailability and binding characteristics for in vivo applications, and the second hindrance is that the SELEX process is usually time-consuming and suffers from low success rates. Aptamer applications, especially in models different from or superior to those of monoclonal antibodies, are briefly introduced
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