Combinatorial selection of a single stranded DNA thioaptamer targeting TGF-β1 protein

A phosphorothioate single-stranded DNA aptamer (thioaptamer) targeting transforming growth factor-β1 (TGF-β1) was isolated by in-vitro combinatorial selection. The aptamer selection procedure was designed to modify the backbone of single-stranded DNA aptamers, where 5′ of both A and C are phosphorothioates, since this provides enhanced nuclease resistance as well as higher affinity than that of a phosphate counterpart. The thioaptamer selected from a combinatorial library (5 × 1014 sequences) binds to TGF-β1 protein with an affinity of 90 nM. In this report, sequence, predicted secondary structure, and binding affinity of the selected thioaptamer (T18_1_3) are presented.