Single-electrode electrochemiluminescence immunosensor for multiplex detection of Aquaporin-4 antibody using metal-organic gels as coreactant

Reliable detection of Aquaporin-4 (AQP4) antibodies is crucial for diagnosing Neuromyelitis Optica spectrum disorder (NMOSD). However, cell-based assays, the most reliable approach, are limited by inadequate instruments. This study reports the use of silver metal-organic gels (Ag-MOGs) as coreactants in a single-electrode electrochemical system (SEES)-based electrochemiluminescence (ECL) immunosensor for multiplex detection of AQP4 antibodies. The immunosensor was constructed by modifying the carbon nanotube single-electrode with Ag-MOGs, incubating it with AQP4 peptides, and ultimately enabling the immobilization of AQP4 antibodies. Voltage-induced potential gradients at the electrode triggered the Ru(bpy)₃²⁺ ECL reaction, and reduced emissions caused by AQP4 antibodies were recorded using a smartphone. Under optimal conditions, the immunosensor exhibited a strong linearity (10–1000 ng/mL) with a detection limit of 2.8 ng/mL. Validation of its accuracy, precision, dilutability, and selectivity confirmed robust performance across the diverse parameters. Furthermore, it successfully detected AQP4 antibodies in serum samples from seropositive NMOSD patients. The platform's single electrode design and multiplex capability make it simple, fast and cost-effective. Enhanced accessibility and user-friendliness could position this system as a transformative tool for improving disease diagnosis and treatment, particularly in resource-limited regions.