The increasing prevalence of liver diseases worldwide, particularly in regions like India, underscores the urgent need for affordable, portable, and efficient diagnostic tools. Traditional liver disease detection methods, such as enzyme-linked immunosorbent assays (ELISAs) and spectrophotometric tests, often require expensive instrumentation and specialized personnel, making them unsuitable for point-of-care (POC) applications. In this context, the laser direct writing (LDW) technique, specifically Laser-Scribed Graphene (LSG) electrodes, offers a promising alternative due to its ability to rapidly and precisely pattern electrochemical sensors without the need for masks or chemicals. LSG electrodes, derived from polyimide (PI) films, exhibit high porosity, electrical conductivity, and electrocatalytic activity, making them ideal for sensitive biosensing applications. However, challenges such as the distribution of electrolytes and the complexity of passivation processes in electrochemical sensor fabrication can compromise their performance. To address these limitations, interfacing LSG electrodes with paper substrates has emerged as a novel solution. Paper's capillary action improves electrolyte distribution, reduces fabrication steps, and enhances electrode reuse, while also enabling the incorporation of enzyme-free and mediatorless detection strategies. This interface concept is particularly beneficial for detecting liver biomarkers such as bilirubin, a critical indicator of liver dysfunction, which can help diagnose conditions like jaundice and hyperbilirubinemia. By combining the advantages of LSG electrodes and paper interfacing, this approach presents a low-cost, efficient, and scalable solution for the early detection of liver diseases, particularly in resource-limited settings.
The fabrication of LSG electrodes using optimized laser power at 35% with a 30 W CO₂ laser resulted in electrodes with superior structural and electrochemical properties, including enhanced crystallinity, balanced porosity, and improved mechanical stability. Characterization through XRD, Raman spectroscopy, SEM, and BET analysis revealed a high specific surface area of 20.8 m²/g and excellent diffusion coefficients of 37 × 10⁻⁶ cm²/s, indicating superior electrochemical kinetics. Cyclic voltammetry further confirmed the enhanced performance across scan rates from 20 to 100 mV/s. These optimized electrodes were successfully utilized for the noninvasive detection of bilirubin, demonstrating exceptional selectivity and specificity with a broad linear detection range of 1 µM to 750 µM. This study highlights the critical role of laser power in tailoring LSG electrode properties for advanced biosensing applications.
In conclusion, the LSG-based electrochemical biosensor developed in this study presents a highly effective platform for the noninvasive detection of bilirubin from urine. This sensor offers significant advantages, including portability, miniaturized design, and the elimination of complex modifications such as enzyme or nanomaterial functionalization on the electrode surface. With high selectivity and specificity toward bilirubin, the biosensor ensures accurate detection while requiring minimal sample volume and reduced analysis time, making it highly practical for point-of-care diagnostics. These features, combined with the ease of fabrication and cost-effectiveness of LSG electrodes, underscore the potential of this biosensor for rapid and reliable bilirubin monitoring in clinical and resource-limited settings.
