A novel electrochemical imprinted sensor for ultrasensitive detection of the new psychoactive substance "Mephedrone"

Identification and quantitation of mephedrone as one of the popular new psychoactive substances (NPSs) in biological fluids is important. In this study, a novel electrochemical imprinted sensor was designed for ultrasensitive and selective measurement of mephedrone, based on sol-gel molecular imprinted polymer, polytyramine and functionalized multi-walled carbon nanotube@ gold nanoparticles (f-MWCNT@AuNPs) nanocomposite. The developed electrochemical sensor inherits characteristics of the gold and MWCNTs such as high electrical conductivity, large specific surface area and good biocompatibility. Also, tyramine as an additional monomer was used for fabrication of a strongly adhering film on the surface of the electrode. In the proposed method, the concentration of mephedrone was determined indirectly. The change in the current response of [Fe(CN)₆]^3-/4- redox probe in the presence and absence of mephedrone molecules was used for indirect measurement of mephedrone molecule in solution. Density functional theory (DFT) was applied to better understanding the interactions between the mephedrone, sol-gel polymer and tyramine from molecular viewpoint. Under the optimized experimental conditions, the calibration curve of the designed sensor was plotted and two dynamic linear ranges from 1 to 10 nM and 10-100 nM with a limit of detection (LOD) as low as 0.8 nM (142 pg ml^-1) were obtained. Finally, the fabricated sensor was successfully used to detect the mephedrone in biological samples.