ssDNA aptamers that recognize diclofenac and 2-anilinophenylacetic acid

A series of 56 ssDNA aptamer variants that bind to diclofenac (DCF) were selected from an initial pool of 2.4 × 10¹⁴ ssDNA molecules by Flu-Mag SELEX process. Sequence analysis of these aptamer variants showed three major groups based on sequence similarity in their random N40 sequences. Out of these, four aptamers designated as D10/DA24, D22, D16, and D3 showed high affinity to DCF with K_d values 100.64, 166.34, 148.73, and 42.7 nM, respectively. Secondary structures of these aptamers showed highly distinct features with typical stem and loop structures. Specificity tests with these four aptamer variants showed that D3 aptamer had higher specificity to DCF followed by 2-anilinophenylacetic acid (2APA), a structural analog of DCF. Whereas aptamers D16 and D22 showed higher specificity to 2APA compared to DCF as target used during selection process. Further, the D10/DA24 aptamer showed high affinity but no specificity to DCF. The DCF aptamers selected can be potential candidates for drug-delivery systems, specific detection of DCF and its derivatives in pharmaceutical preparations and contaminants.