Nucleic acid aptamers are oligonucleotide sequences screened by an in vitro methodology called Systematic Evolution of Ligands by Exponential Enrichment (SELEX). Known as “chemical antibodies”, aptamers can achieve specific recognition towards the targets through conformational changes with high affinity, and possess multiple attractive features including, but not limited to, easy and inexpensive to prepare by chemical synthesis, relatively stable and low batch-to-batch variability, easy modification and signal amplification, and low immunogenicity. Now, aptamers are attracting researchers' attentions from more than 25 disciplines, and have showed great potential for application and economic benefits in disease diagnosis, environmental detection, food security, drug delivery and discovery. Although some aptamers exist naturally as the ligand-binding elements of riboswitches, SELEX is a recognized method for aptamers screening. After thirty-two years of development, a series of SELEX methods have been investigated and developed, as well as have shown unique advantages to improve sequence performances or to explore screening mechanisms. This review would mainly focus on the novel or improved SELEX methods that are available in the past five years. Firstly, we present a clear overview of the aptamer's history, features, and SELEX development. Then, we highlight the specific examples to emphasize the recent progress of SELEX methods in terms of carrier materials, technical improvements, real sample-improved screening, post-SELEX and other methods, as well as their respects of screening strategies, implementation features, screening parameters. Finally, we discuss the remaining challenges that have the potential to hinder the success of SELEX and aptamers in practical applications, and provide the suggestions and future directions for developing more convenient, efficient, and stable SELEX methods in the future.

核酸适体是通过称为指数富集配体系统进化（SELEX）的体外方法筛选的寡核苷酸序列。适配体被称为“化学抗体”，可以通过高亲和力的构象变化实现对靶标的特异性识别，并具有多种吸引人的特点，包括但不限于化学合成制备简单、成本低廉、相对稳定、批次成本低等。 -批次可变性、易于修饰和信号放大、免疫原性低。现在，适配体正吸引超过25个学科的研究人员的关注，并在疾病诊断、环境检测、食品安全、药物输送和发现等方面显示出巨大的应用潜力和经济效益。尽管一些适体作为核糖开关的配体结合元件天然存在，但 SELEX 是公认的适体筛选方法。经过32年的发展，一系列SELEX方法被研究和发展，并在提高序列性能或探索筛选机制方面显示出独特的优势。本次审查将主要关注过去五年中可用的新颖或改进的 SELEX 方法。首先，我们对适体的历史、特征和SELEX的发展进行了清晰的概述。然后，我们通过具体实例强调SELEX方法在载体材料、技术改进、真实样品改进筛选、post-SELEX等方法方面的最新进展，以及它们的筛选策略、实现特点、筛选等方面。参数。最后，我们讨论了可能阻碍SELEX和核酸适体在实际应用中取得成功的剩余挑战，并为未来开发更方便、高效和稳定的SELEX方法提供建议和未来方向。