Development of Lab-made Flexible Screen-printed Electrode based on S-Graphene Enriched with AuNPs and CuO for Electrochemical Detection of Tyrosine

Abstract Tyrosine (Tyr) is an amino acid that serves as a precursor for the synthesis of numerous neurotransmitters in the human body. This study aimed to design paper-based lab-made screen-printing electrodes (SPE) for tyrosine determination using a flexible electrochemical sensor. To achieve this, conductive inks with this composition were developed for the first time in the literature by incorporating sulfur (S)-doped graphene, synthesized using Yucel's method, as well as gold nanoparticles and copper oxide (CuO) as conductive fillers, which were then integrated into flexible paper substrates. The optimized electrodes (CuO/S-G/AuNPs/SPE) were used to investigate the best oxidation response to tyrosine. Characterization of CuO/S-G/AuNPs/SPE was performed using electrochemical impedance spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and field emission scanning electron microscopy. The sensor had a limit of detection of 0.024 µM and a limit of quantitation of 0.08 µM. In addition, the sensor's affordability and ease of use make it advantageous for practical applications. The results demonstrate the sensor's stability and reproducibility in measuring tyrosine. It is anticipated that the proposed sensor can effectively detect tyrosine in sweat samples and serve as a non-invasive, wearable, flexible sensor in the future.