Strategies for Improving Aptamer Screening Efficiency: Library Design, Awareness Innovation, and Instrument Assistance.

Aptamers, as short single-stranded nucleic acids, can bind to targets in a similar way to antibodies. Relying on the advantages of low cost, high stability, and flexibility, they are widely applied in biosensors, disease therapy, and synthetic biology. As an aptamer screening method, the Systematic Evolution of Ligands by Exponential Enrichment (SELEX) offers almost unlimited possibilities for functional aptamer generation. However, at present, the SELEX procedure has not reached a satisfactory level, and it still faces some challenges in practical application, such as the relatively blind initial library, laborious and time-consuming selection process, typically requires 9-20 rounds for screening, and the entire process generally extends over 2-3 months, and sub-optimal performance of aptamers obtained. In the past few years, researchers have made great efforts to address these obstacles. Hence, in this review, we first summarize the aptamer screening mechanism and the existing limitations of SELEX. Then analyze the principle and technical key points of the SELEX optimization screening strategy. By incorporating rational library design, novel screening awareness, and advanced screening equipment, the number of aptamer screening cycles is significantly reduced to <8 rounds, with some methods achieving single-round screenings. This has led to a considerable decrease in the overall screening time to <3 weeks, while simultaneously enhancing the performance of the aptamers. Finally, critically discuss the present challenges and future directions of aptamer screening. This review aims to provide a practical reference for designing suitable aptamer screening methods.