Electrochemical determination of metformin via a carbon paste electrode modified with an Ag NPs/Cu₂O/CuO-decorated...

Metformin (MET) is widely used in the treatment of diabetes either alone or in combination with other drugs, in drug discovery to evaluate the anti-diabetic potential of other drugs, and usually as a comparison compound in pharmacokinetics/pharmacodynamics studies. Measuring the concentration of this substance is very important both pre-clinically in different species and clinically in the medical monitoring of diabetic patients to prevent toxicity and ensure adherence to described drugs. Therefore, it is very important to develop a sensitive and selective method to measure MET. In this work, a new electrochemical biosensor based on a carbon paste electrode, modified with bacterial nanocellulose, copper oxide, and silver nanoparticles (Ag NPs/Cu₂O/CuO/BNC/CPE) was used for high-sensitivity MET determination. The morphology and structure of this bio-nanocomposite were characterized by ATR-IR, FE-SEM, EDS, mapping, XRD, and DRS techniques. Compared with the CPE electrode, the Ag NPs/Cu₂O/CuO/BNC/CPE modified electrode showed much higher electrocatalytic activities toward the oxidation of MET. The measurements were carried out by the cyclic voltammetry technique. Surface conductance was evaluated using the impedance technique. The results showed an increase in surface conductivity. The detection limit was obtained at 42.3 nM and two linear ranges 0.1-76 and 76-1000.0 μM were observed. The developed sensor had good features such as high sensitivity, reproducibility and repeatability, low detection limit, and fast response time. The obtained results from the real sample (MET tablets) were completely satisfactory.