Microperoxidase-11 modified mesoporous SnO2 film electrodes for the detection of antimalarial drug artemisinin

This work presents a simple and efficient preparation method for microperoxidase-11 (MP11) modified mesoporous SnO2 films on ITO glass substrates (MP11/DDAB/SnO2/ITO) for the development of a sensitive electrochemical drug sensor for the determination of antimalarial endoperoxide artemisinin (ART). Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier Transform-Infrared Spectroscopy (FT-IR) and UV-vis absorption spectroscopy were used to characterize the resultant modified electrodes. The properties of the electrode enable a high MP11 loading to be achieved in a stable and functional way allowing the direct reduction and oxidation of the immobilized undeca-peptide. The MP11 modified electrodes exhibited significant catalytic activity for the electrochemical reduction of ART around -0.43 V vs. Ag/AgCl in NaH2PO4 pH 7 buffer by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results showed a sensitive response; the cathodic catalytic current was linearly proportional to the concentration of ART in the range 0-150 mu M (R = 0.9895) when using DPV with a limit of detection of 17 mu M. This type of sensor has demonstrated good repeatability, reproducibility and stability and was found to be applicable for use in determining ART concentrations in extracts from the plant Artemisia annua purchased from local pharmaceutical stores. Finally due to the optical transparency of the SnO2 film electrodes, the reaction of immobilized MP11 with ART was also monitored using UV-vis spectroscopy indicating the formation of MP11/ART adducts on the surface of the film electrode.