Nano RNA aptamer wire for analysis of vitamin B₁₂.

A simple and stable RNA aptamer-based colorimetric sensor for the detection of vitamin B₁₂ using gold nanoparticles (AuNPs) has been proposed. Vitamin B₁₂ belongs to the B vitamin group and prevents pernicious anemia, which is caused by vitamin B₁₂ deficiency. A highly stable RNA aptamer that binds to vitamin B₁₂ was employed by structural modification of 2'-hydroxyl group of ribose to 2'-flouro in all pyrimidines indicated in lowercase in 35-mer aptamer (5' GGA Acc GGu GcG cAu AAc cAc cuc AGu GcG AGc AA 3'). Aggregation of AuNPs was specifically induced by desorption of the vitamin B₁₂ binding RNA aptamer from the surface of AuNPs as a result of the aptamer-target interaction, leading to the color change from red to purple. The level of detection of vitamin B₁₂ was 0.1 μg/ml by successful optimization of the amount of the aptamer, AuNPs, salts, and stability of the aptamer. Analysis of vitamin B₁₂ was carried out, and the observed recovery was 92 to 95.3% with a relative standard deviation in the range of 2.08 to 8.27%. The results obtained were compared with those of the ultraviolet-visible (UV-vis) spectrometry method. This colorimetric aptasensor is advantageous for on-site detection with the naked eye.