Research advances of aptamers selection for protein targets

Aptamers are selected through systematic evolution of ligands by exponential enrichment (SELEX), and are artificially synthesized single-stranded DNA or RNA with high affinity and specificity against a wide variety of target molecules. Since some functional proteins play the key role in life process, aptamers against proteins have attracted great attention in the last decade, and are used in basic research and wide applications. The performance of aptamers depends on their affinity, specificity and stability. In recent years, many SELEX methods have been developed to enhance the properties of aptamers, improve selection efficiency and reduce cost. The main procedure of SELEX includes the isolation of target-aptamer compound, optimization the random ssDNA library, enrichment of ssDNA and the analysis and characterization of selected aptamers. In this review, we summarize the developments of aptamer selection methods for protein targets since 2005, discuss their shortcomings and limitations, and introduce the optimization of ssDNA library, aptamer sequence character and analytical methods for their affinity analysis.