ABSTRACT
This chapter describes Systematic evolution of ligands by exponential enrichment (SELEX) strategies with methodological improvements, well established since the first application in aptamer development. It presents a brief description of post-SELEX improvements of aptamers that enable the development of aptamers with desired binding properties and functions. Post-SELEX strategies to improve and fine-tune aptamer functions have also been established. In vitro recombination and reselection from partially randomized aptamers have been shown to achieve improvement of binding properties for specific targets. In vitro selection and improvement have been extensively explored for aptamer development. While cell-SELEX can target only membrane-associated proteins, aptamers against any unpurified proteins in a crude sample or tissue samples can be obtained by SELEX combined with polyacrylamide gel electrophoresis and electroblotting. In aptamers, multimerization of single or multiple aptamers often offers dramatically higher affinity and specificity than monovalent binding.
