Electrochemical analysis of oseltamivir drug active agent used in the treatment of Covid–19 with DNA biosensor

Various antiviral drugs are used for the treatment of COVID–19, and various drugs are under investigation. Promising clinical results have been obtained in the treatment of COVID–19 by using favipiravir (FAV), alpha–interferon, umifenovir, remdesivir (RMD), ribavirin, lopinavir (LPV)–ritonavir, oseltamivir (OST) etc. drug active agents. In this study, quantitative analysis of OST, the drug active ingredient used in the treatment of COVID–19, was carried out using electrochemical techniques. Thus, an electrochemical sensor has been developed that can be used in the quality control of the drug dose in drug production stages and can be used in drug design studies by monitoring the urinary excretion of the active substance. For this purpose, a modified glassy carbon electrode was used as a working electrode. The glassy carbon electrode alone can not detect the presence of OST. Therefore, guanine base, which was determined to interact with OST and found in the DNA structure, was used as an agent. The guanine base in the DNA structure was immobilized on the glassy carbon electrode by using glutardialdehyde, a crosslinker (GA2–Guanine/CKE electrode). The sensor, which enables the electrochemical analysis of OST, offered a fast, low–cost and high–accuracy analysis opportunity. Using the differential pulse voltammetry technique, a well–defined irreversible oxidation signal at approximately +0,45 V (vs. Ag/AgCl) in Britton‒Robinson buffer (BR; pH 11,0) was used for analysis. This developed electrode and method has been successfully applied to find the amount of OST present in pharmaceutical formulation and human urine samples. Two working ranges were determined for the BR buffer solution, tablet sample, and urine sample, with the lowest detection limits (LOD) calculated as 7,16×10−9 mol·L−1, 9,05×10−9 and 6,19×10−6 mol·L−1, respectively. The recovery rate for the proposed sensor ranges between 86,6% and 103,5%.