A turn-on unlabeled colorimetric biosensor based on aptamer-AuNPs conjugates for amyloid- β oligomer detection

Amyloid- beta oligomers (A beta O) have been identified as core biomarkers for early diagnosis of Alzheimer's disease (AD). For the first time, a turn-on unlabeled colorimetric aptasensor based on aptamer-polythymine (polyT)polyadenine (polyA)-gold nanoparticles (pA-pT-apt@AuNPs) was developed for highly sensitive and specific detection of amyloid- beta(1-40) oligomers (A beta 40-O). In this system, polyA sequence could preferentially anchor onto AuNPs surface as well as reduce the non-specific adsorption, and the aptamer could form upright conformation for the specific recognition of A beta 40-O. The aggregation of pA-pT-apt@AuNPs was induced by MgCl2. However, the addition of A beta 40-O enabled the aptamer fold adaptively upon recognition and aptamer-A beta 40-O complex formed surrounding AuNPs, effectively stabilizing pA-pT-apt@AuNPs against salt-induced aggregation, therefore the color of pA-pT-apt@AuNPs solution still retained red. Based on this principle, the proposed aptasensor exhibited high sensitivity with the limit of detection of 3.03 nM and a linear detectable range from 10.00 nM to 100.0 nM. The superb sensitivity was achieved via the optimization of the length of polyA and polyT spacer. This pA-pT-apt@AuNPs based colorimetric aptasensor provides a rapid, cost-effective, highly sensitive detection method for A beta 40-O, which is valuable for the early diagnosis of AD.

Automated summary

A turn-on unlabeled colorimetric aptasensor based on aptamer-polythymine (polyT)polyadenine (polyA)-gold nanoparticles (pA-pT-apt@AuNPs) was developed for highly sensitive and specific detection of amyloid- beta(1-40) oligomers (A beta 40-O), which is valuable for the early diagnosis of Alzheimer's disease (AD).