A label-free electrochemical biosensor based on a DNA aptamer against codeine

•A novel DNA aptamers against codeine were generated by SELEX in this article.•A novel electrochemical label-free codeine aptamer biosensor was developed.•A very low detection limit was achieved.•The optimal conditions for aptamer binding were studied by us.•We studied the secondary structure of aptamer.

In order to develop a sensor for opium alkaloid codeine detection, DNA aptamers against codeine were generated by SELEX (systematic evolution of ligands by exponential enrichment) technique. An aptamer HL7-14, which is a 37-mer sequence with Kd values of 0.91 μM, was optimized by the truncation-mutation assay. The specificity investigation shows that HL7-14 exhibits high specificity to codeine over morphine, and almost cannot bind to other small molecule. With this new selected aptamer, a novel electrochemical label-free codeine aptamer biosensor based on Au-mesoporous silica nanoparticles (Au-MSN) as immobilized substrate has been proposed using [Fe(CN)6]3−/4− as electroactive redox probe. The linear range covered from 10 pM to 100 nM with correlation coefficient of 0.9979 and the detection limit was 3 pM. Our study demonstrates that the biosensor has good specificity, stability and well regeneration. It can be used to detect codeine.

Graphical abstractThe stepwise procedure of electrochemical aptamer sensor.Figure optionsDownload full-size imageDownload as PowerPoint slide