A Universal Electrochemical Biosensor Using Nick-HCR Nanostructure as Molecular Gate of Nanochannel for Detecting Chromium(III) Ions and MicroRNA

Solid-state nanochannels demonstrating excellent mechanical properties and chemical stability combined with programmable DNA provide an opportunity to control on-demand ion transport. However, poor functionalization of the nanochannels limits the types of detected targets, as well as its universality in the sensing field. To solve these issues, a universal nanochannel sensing platform was developed by employing a nick hybridization chain reaction (nHCR) nanostructure as a molecular gate, which could generally respond to the universal sequence Y. Metal ion-dependent DNAzyme cleavage was used to transfer the chromium­(III) (Cr³⁺) ions into nucleic acid X, which was further amplified and converted into universal sequence Y. Upon adding sequence Y into the nHCR nanostructure-functionalized nanochannel, the disassembly of the nHCR molecular gate turned on the ionic current signal inside the nanochannel. The ON–OFF ratio displayed a linear relationship with the Cr³⁺ concentration in the range from 200 fM to 20 nM. In less than 66 min, the nanochannel-based biosensing platform successfully detected Cr³⁺ ions as low as 200 fM. In addition, the detection of microRNA with a concentration as low as 1 pM was achieved by only regulating the sequence of template X′–Y′.