Highly Sensitive LIG-Derived Electrochemical Biosensor for Simultaneous Detection of Aβ42/Aβ40 Ratio in Alzheimer’s Early Diagnosis

Abstract

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder characterized by the accumulation of amyloid-beta (Aβ) plaques in the brain. Recent clinical studies indicate that the ratio of Aβ42 to Aβ40 in blood plasma is a more reliable biomarker for early AD screening than individual peptide concentrations, as it reflects the brain's Aβ sequestration. However, detecting these biomarkers in blood remains challenging due to their ultra-low abundance and the structural similarity between Aβ42 and Aβ40. In this work, we developed an electrochemical biosensor using laser-induced graphene (LIG) electrodes, fabricated via one-step CO 2 laser scribing on polyimide. To optimize the interface for antibody immobilization, a low-damage plasma treatment (LDPT) was strategically employed to introduce nitrogen-containing functional groups (e.g., amine groups) onto the LIG surface. This plasma-assisted modification creates highly reactive sites that facilitate the stable and high-density covalent bonding of specific Aβ42 and Aβ40 antibodies via their carboxyl groups, ensuring a robust bio-interface without compromising the structural integrity of the graphene lattice. The resulting LIG-based biosensors demonstrated exceptional sensitivity, achieving a limit of detection (LOD) at sub-picomolar concentrations. To validate the clinical diagnostic potential, we examined the sensor's specificity by preparing a series of samples with predefined Aβ42/Aβ40 concentration ratios. These samples were tested on Aβ42 and Aβ40-antibody-modified sensors, respectively. The results indicated that the detected concentration ratios were highly consistent with the known concentrations, confirming the platform's high fidelity and cross-reactivity resistance for the precise determination of the Aβ42 to Aβ40 ratio in complex analytical scenarios. By leveraging LDPT for surface functionalization, we have developed a robust and sensitive LIG-based electrochemical biosensing platform of electrochemical biosensors. This approach provides a scalable and cost-effective solution for the simultaneous detection of Aβ biomarkers, supporting the development of portable point-of-care devices for early Alzheimer’s intervention.