A sensitive and label-free impedimetric biosensor based on an adjunct probe

•A label-free impedimetric sensor is constructed for DNA sequences detection.•The key point is adjunct probes immobilized nearby capture probes.•The biosensor achieves simple and highly selective detection for DNA sequence.•The sensor is readily extended for other biomolecules, proteins and mRNAs detection.

A highly sensitive and label-free impedimetric biosensor is achieved based on an adjunct probe attached nearby the capture probe. In this work, the adjunct probe was co-assembled on the surface of gold electrode with the capture probe hybridized with the reporter probe, and then 6-mercapto-1-hexanol was employed to block the nonspecific binding sites. When target DNA was added, the adjunct probe functioned as a fixer to immobilize the element of reporter probe displaced by the target DNA sequences and made the reporter probe approach the electrode surface, leading to effective inhibition of charge transfer. The increase in charge transfer resistance is related to the quantity of the target DNA in a wide range. The linear range for target DNA with specific sequences was from 0.1 nM to 0.5 μM with a good linearity (R = 0.9988) and a low detection limit of 6.3 pM. This impedimetric biosensor has the advantages of simplicity, sensitivity, good selectivity, and large dynamic range.

Graphical abstractUsing an adjunct probe for highly sensitive and label-free detection of DNA sequence based on electrochemical impedance spectroscopy was achieved.Figure optionsDownload full-size imageDownload as PowerPoint slide