A Highlight of Recent Advances in Aptamer Technology and Its Application

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.

Keywords: SELEX; application; aptamer; improvement; modification; optimization.

Figure 1

Schematic diagram of aptamer conformational recognition of targets to form an aptamer-target complex.

Figure 2

Important advantages of aptamers over antibodies in clinical applicability and industrialization.

Figure 3

Schematic diagram of the SELEX process steps.

Figure 4

Some representative models of modified aptamers for disease diagnosis and therapy. (a) An aptamer labeled with a fluorochrome is used as a sensitive bioimaging probe; (b) Tumor cell-activated aptamer-reporter with paired fluorochrome-quencher molecules are used in rapid, one-step, high-throughput assays for circulating tumor cells within drops of blood; (c) Switchable aptamer-based fluorochrome-quencher reporter are used as precisely controlled, target-triggered, bioimaging probes; (d) The simple, but effective, aptamer-doxorubicin conjugates; (e) Aptamer-gene drug chimera used for targeted delivery of gene-silencing tools.