Truncated affinity-improved aptamers for 17β-estradiol determination by AuNPs-based colorimetric aptasensor

•76-mer aptamer was intercepted at multiloop, hairpin or interior loop for first time.•Binding domain was ascertained by affinity comparison of 19 truncated aptamers.•15-mer truncated aptamer obtained with improved affinity and specificity.•This work provided proof-of-concept study for other long aptamers truncation. 17β-estradiol (E2) residues could enrich in organisms via food chain and lead to harmful biological effects for human body. To ascertain the binding domain of original E2 aptamer (E00) with long-sequence (76-mer), we developed novel truncated aptamers from E00, through rationally designed truncation by intercepting a single ring or a combination of rings (containing hairpin loop, interior loop or multiloop) at different sites and retaining appropriate double helix regions. Through comparison, 15-mer E09 presented improved affinity and higher specificity, indicating the hairpin loop near to 3′ end of E00 served on the binding domain to E2. E09 was used for gold nanoparticles (AuNPs)-based colorimetric determination of E2, achieved the detection limit of 0.02 μg/mL. The truncated aptamer (only 15-mer) first proposed in this study has great application potential in E2 determination, and this work provides proof-of-concept study for truncation of other long-sequence aptamers.