Laser-induced graphene electrode modified by platinum nanoparticle/zein/ gelatin/glucose oxidase for non-invasive glucose sensor in multiple biofluids

Background: A non-invasive glucose biosensor for multiple biofluids based on platinum nanoparticle (Pt-NP)- modified laser-induced graphene (LIG) electrodes coated with a zein/gelatin/glucose oxidase (GOx) for amperometric detection of glucose is created. The biosensor fabrication is cost-effective and scalable, as it combines simple LIG electrode fabrication with direct Pt-NP electrodeposition and a sequence of drop-and-dry steps for zein and gelatin layer then GOx enzyme. The Pt-NP modification on the LIG electrode functions as an electrocatalyst to enhance the anodic H2O2 signal, which is directly proportional to glucose concentration. The zein layer acts as a diffusion barrier to mitigate potential interferences, while the gelatin film provides amine groups for the glutaraldehyde-mediated immobilization of the GOx enzyme. Results: The key parameters of LIG were optimized, such as power laser, number of Pt-NP cycles, and zein concentration. In addition, LIG was characterized by Raman spectroscopy, SEM, and cyclic voltammetry (CV) to ensure graphitization and electron transfer performance. The as prepared LIG/Pt-NP/Zein/Gel-GOx glucose biosensor was in anodic H2O2 detection mode and tested for glucose measurements in multiple biofluids including sweat, saliva, and urine. At H2O2 detection potential of +0.4 V, a linear detection range from 0 up to 2 mM glucose was obtained with a limit of detection (LOD) of 0.01 mM, making it feasible for glucose determination in various clinically relevant biofluids. By comparing with the commercial SPE, this LIG-based sensor offered much higher detection sensitivity towards both H2O2 and glucose, making it a superior choice for electrochemical analysis. Significance: This LIG/Pt-NPs/Zein/Gel-GOx offers a practical and high sensitivity approach to glucose measurement with a wide linearity for multiple biofluids. Given the straightforward and easily scalable process, this high-performance, LIG-based glucose biosensor presents a compelling alternative over commercial screen-printed electrode. Highlighted the novelty using zein as a protective layer to reduce interferences. Owing to the simplicity of fabrication with high potential for up-scaling, this high analytical performance biosensor might be an alternative tool for multiplex glucose biosensors in point-of-care applications.