Disposable Printed Electrode Made with Chinese Shellac and Carbon Black for Melatonin Detection

Screen-printed electrodes (SPEs) are an innovative technology in electrochemical sensors, offering advantages such as easy fabrication, large-scale production, low cost, and potential for miniaturization. These electrodes can be disposable and customized for various applications. Due to these advantages, SPEs are gaining attention in fields such as medicine and pharmacy. In this study, an electrochemical sensor was developed through screen-printing, using new conductive ink, compounded with carbon black, Chinese shellac, and acetone. The device was characterized by different approaches to analyze its characteristics, including scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetry, and contact angle. Also, the electrochemical characterizations were performed by using cyclic voltammetry and impedance spectroscopy. The sensor was employed to detect melatonin, a sleep-regulating hormone, and, under optimized parameters, the analytical curve by differential pulse voltammetry exhibited a linear range from 1.0 to 100 μmol L^–1, with a limit of detection of 0.1 μmol L^–1. The device was applied to synthetic urine samples using the addition and recovery method, yielding recovery values from 86.7 to 110%. The results indicate that the conductive ink is suitable for manufacturing printed electrodes, and the device proved promising for melatonin detection.