Nanostructured composites based on graphene and nanoparticles of cobalt in the composition of monoamine oxidase biosensors for determination of antidepressants

Amperometric monoamine oxidase biosensors based on screen-printed graphite electrodes modified with nanostructured reduced graphene oxide (RGO) composites and cobalt nanoparticles (CoNPs) were developed to determine antidepressant drug substances: tianeptine, thioridazine, and fluoxetine. Combinations of carbon nanomaterials with metal nanoparticles (nanocomposites) along with retaining the properties of individual components, also provide a new quality of the developed devices due to their joint contribution. The nanomaterial-modifier was applied to the surface of screen-printed graphite electrodes using dropwise evaporation. Fixing of RGO on the surface of the screen-printed graphite electrodes occurs due to electrostatic interaction between RGO carboxyl groups and amine groups of the amine derivative on the platform of polyester polyol (H20–NH2). The CoNPs were obtained electrochemically by the method of chronoamperometry at a potentialE= – 1.0 V and different time of their accumulation (about 50 – 60 sec) on the electrode surface. According to the data of atomic force microscopy, the predominant size of CoNPs is (40 ± 2) and (78 ± 8) nm, depending on the time of electrochemical deposition of NPs. Data of electrochemical impedance spectroscopy show that nanocomposites RGO-chitosan/CoNPs and RGO-amine derivative on the polyester polyol (H20–NH2)/CoNPs platform are characterized by the lowest values of the charge transfer resistance. The use of those nanocomposites modifying the electrode surface significantly improved the analytical characteristics of the developed biosensors providing a wider range of operating concentrations from 1 × 10–4to 5 × 10–9mol/liter, greater sensitivity coefficient, better correlation coefficient, and lower limit of the detectable concentrations. A possibility of using biosensors to control the quality of antidepressants upon determination of the main active substance in medicinal drugs and biological fluids is shown. The lower limit of detectable concentrations (7 – 9) × 10–10mol/liter is attained when using tyramine as a substrate for determination of fluoxetine, thioridazine and tianeptine, respectively.