Carbon quantum dots co-catalyzed with multiwalled carbon nanotubes and silver nanoparticles modified nanosensor for the electrochemical assay of anti-HIV drug Rilpivirine

In this study, a novel and sensitive voltammetric nanosensor has been developed for the first time, for the detection of Rilpivirine based on amine-functionalized multiwalled carbon nanotubes (NH2-fMWCNT) with Ag nanoparticles onto carbon quantum dots modified glassy carbon electrode. Scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were employed for characterization of the modified electrode. The Rilpivirine showed two irreversible oxidation peaks at 1.20 V and 1.42 V, at all the investigated pH values. The cyclic voltammetry results demonstrated excellent electrocatalytic activity of the modified electrode toward the oxidation of Rilpivirine as endorsed by the enhanced current responses compared to bare electrode. The electrochemical catalytic activity was further utilized as a sensitive detection method for the investigation of the redox mechanism of Rilpivirine using differential pulse voltammetry (DPV). For experimental conditions optimization the influence of supporting electrolyte and pH was examined and 0.5M H2SO4 was selected as the best electrolyte for getting intense current signals of the target analyte. The relationship of anodic peaks potentials for peak 1 and peak 2 (EP1 and EP2) with pH values and scan rate was also studied. Scan rate results showed that the oxidation of Rilpivirine at the nanosensor surface occurs under adsorption controlled manner. Therefore, differential pulse adsorptive stripping voltammetric technique was employed for the determination of Rilpivirine. Optimum accumulation potential and time were found as 0 V and 60 s, respectively. Under these optimum conditions, response of Rilpivirine demonstrated a linear behavior in the concentration range from 1.00 x 10(-9) to 7.00 x 10(-9) M, with a limit of detection value of 3.00 x 10(-11) M and 6.40 x 10(-11) M for peak 1 and peak 2 in aqueous medium containing 0.5M H2SO4 as supporting electrolyte, respectively. Interferences studies were achieved in the presence of 500 fold higher concentration of interfering agents to check the selectivity of the developed method. The designed method was successfully applied for the determination of Rilpivirine in biological fluids, urine and synthetic human serum as a real sample. The value of limit of detection were found to be 1.79x10(-10) M, 4.47 x 10(-10) M in serum samples, 5.26 x 10(-10) M and 8.27 x 10(-10) M in urine samples for peak 1 and peak 2, respectively. Recovery experiments were carried out to check the accuracy and precision of the designed method. Moreover, the repeatability, reproducibility and stability of the modified electrode in supporting electrolyte, serum and urine samples were investigated.