Current developments of SELEX technologies and prospects in the aptamer selection with clinical applications

Abstract

Aptamers are single-stranded oligonucleotide sequences capable of binding to specific ligands with high affinity. In this manner, they are like antibodies but have advantages such as lower manufacturing costs, lower immunogenicity, fewer batch-to-batch differences, a longer shelf life, high tolerance to different molecular milieus, and a greater number of potential targets. Due to their special features, they have been used in drug delivery, biosensor technology, therapy, and diagnostics. The methodology that allowed its production was the "Systematic Evolution of Ligands by Exponential enrichment" (SELEX). Unfortunately, the traditional protocol is time-consuming and laborious. Therefore, numerous variants with considerable optimization steps have been developed, nonetheless, there are still challenges to achieving real applications in the clinical field. Among them, are control of in vivo activities, fast renal filtration, degradation by nucleases and toxicity testing. This review focuses on current technologies based on SELEX, the critical factors for successful aptamer selection, and its upcoming biomedical and biotechnological applications.

Keywords: Aptamer; Biosensing techniques; Biotechnology; Nucleic acids; SELEX.

Fig. 1

Schematic representation of DNA aptamers and RNA aptamers selection through conventional SELEX methodology. A synthetic library of ssDNA or ssRNA molecules with random sequences is created (A). These molecules are mixed with the target to form aptamer-target complexes (B). Non-specific sequences are removed, and specific aptamers are isolated (C). The selected aptamers are amplified through PCR to enrich the library (D). This process is repeated in several cycles to enhance specificity (D). Finally, the aptamers are sequenced and characterized (E).

Fig. 2

Biomedical applications of aptamers in virus inhibition and detection. A. Inhibition of SARS-CoV-2 through the binding of an aptamer to the RBD (receptor binding domain) protein, blocking its interaction with the ACE2 receptor on human cells and preventing viral infection. B. Detection of the Zika virus using an aptamer-based biosensor that specifically binds to the virus, enabling rapid and accurate detection.