Quantitative Detection of Potassium Ions and Adenosine Triphosphate via a Nanochannel-Based Electrochemical Platform Coupled with G‑Quadruplex Aptamers

The development of synthetic nanopores and nanochannels that mimick ion channels in living organisms for biosensing applications has been, and still remains, a great challenge. Although the biological applications of nanopores and nanochannels have achieved considerable development as a result of nanotechnology advancements, there are few reports of a facile way to realize those applications. Herein, a nanochannel-based electrochemical platform was developed for the quantitative detection of biorelated small molecules such as potassium ions (K+) and adenosine triphosphate (ATP) in a facile way. For this purpose, K+ or ATP G-quadruplex aptamers were covalently assembled onto the inner wall of porous anodic alumina (PAA) nanochannels through a Schiff reaction between −CHO groups in the aptamer and amino groups on the inner wall of the PAA nanochannels under mild reaction conditions. Conformational switching of the aptamers confined in the nanochannels occurs in the presence of the target molecules, resulting in increased steric hindrance in the nanochannels. Changes in steric hindrance in the nanochannels were monitored by the anodic current of indicator molecules transported through the nanochannels. As a result, quantitative detection of K+ and ATP was realized with a concentration ranging from 0.005 to 1.0 mM for K+ and 0.05 to 10.0 mM for ATP. The proposed platform displayed significant selectivity, good reproducibility, and universality. Moreover, this platform showed its potential for use in the detection of other aptamer-based analytes, which could promote its development for use in biological detection and clinical diagnosis.