Aptamer Molecular Evolution for Liquid Biopsy

Liquid biopsy can provide comprehensive and real-time physiological and pathological information in a noninvasive and longitudinal monitoring manner, facilitating precision medicine practice and clinical investigations. However, the rarity of circulating targets in extremely complex body liquid matrixes poses daunting challenges for liquid biopsy. Aptamers are single-stranded oligonucleotides with unique tertiary structures to selectively bind to their targets with excellent affinity and selectivity. The structural and functional merits of aptamers, including facile evolution, convenient functionalization and assembly, and adjustable affinity, render them ideal recognition ligands for liquid biopsy. This chapter focuses on the molecular evolution of aptamers for liquid biopsy. First, recent progress in molecular evolution strategies of aptamers is summarized including each step during the whole SELEX (systematic evolution of ligands by exponential enrichment) procedures. Then, state-of-the-art approaches of aptamer-based liquid biopsy with the emphasis on isolation and detection of circulating tumor cells and extracellular vesicles are introduced. Finally, the challenges and future perspectives in this field are discussed.