Cost-Effective Fabrication of Laser-Induced Graphene Electrochemical Cell for NADH Detection

The unique properties and versatile applications of laser-induced graphene (LIG) have garnered significant interest for electrochemical sensing technologies. In this study, we report the fabrication and application of an in-house produced LIG/polyimide (PI) composite, generated via 450 nm laser irradiation, for the amperometric detection of Nicotinamide Adenine Dinucleotide (NADH), a critical biomarker associated with several neurodegenerative human diseases. The LIG structure was confirmed by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and sheet resistance measurements, with an average sheet resistance (R _s) of 24.38 ± 2.19 Ω/□, indicating excellent electrical conductivity. XPS analysis revealed the presence of CO bonds (288.9 eV), formed under oxidizing conditions during LIG fabrication, which may contribute to enhanced electrocatalytic activity by facilitating NADH oxidation through redox mediation. Using a printed Ag/AgCl pseudoreference electrode and an applied potential of only 50 mV vs Ag/AgCl, NADH was detected within a concentration range of 5 μmol L^-1 to 10 mmol L^-1. The sensor exhibited a limit of detection (LOD) of 2.72 μmol L^-1 and a limit of quantification (LOQ) of 9.07 μmol L^-1, with a linear response up to 1 mmol L^-1. The repeatability of the electrochemical oxidation of NADH resulted in a relative standard deviation (RSD) of 2.76%, while the reproducibility, evaluated as intra- and interbatch variability, yielded RSD values of 5.78 and 8.22%, respectively. Furthermore, the total material cost for each electrochemical cell was estimated at only U$ 0.10, highlighting the method's potential for low-cost and environmentally friendly biosensor development. The fabricated LIG platform offers a promising route for sensitive, scalable, and sustainable detection of NADH and potentially other clinically relevant analytes.