A label-free electrochemical biosensor for rapid quantification of antimicrobial peptides in teleost fish mucus

We used a thiol-faradaic electrochemical differential pulse voltammetry and impedance spectroscopy on a gold-modified screen-printed carbon electrode to quantify Chrysophsins antimicrobial peptides in the fish mucus without prior extraction. We have developed a specific anti-Chrysophsins polyclonal antibody and used ferrocene as a transducing system. The platform has a sensitivity of 30.5 nA.mL.ng^-1 (11.28 nA.nM^-1) in a linear range of 0.1-1 µg.mL^-1 and a limit of detection of 0.227 ng.mL^-1 (84.15 pM). Selectivity, accuracy, repeatability and stability were validated to meet the guidelines of ligand binding assays. Mean Chrysophsins levels in mucus pools from healthy and thermally unstressed Argyrosomus regius, Dicentrarchus labrax and Sparus aurata fish were 8.763 µM (± 0.007), 7.296 µM (± 0.023) and 8.296 (± 0.044) respectively, within the range of mass spectrometry gill values and below the minimum inhibitory concentration (MIC) of Chrysophsins for fish pathogens. The multi-infected D. labrax pool shows a significant decrease in concentration compared to the healthy and thermally stressed pools (p < 0.0262) with 2.8 µM (± 0.024). The thermally stressed A. regius pool is not significantly different from the other pools with 8.763 µM (± 0.007). This electrochemical platform is a flexible tool for real-time targeting of peptide biomarkers in the real matrix and is suitable for mucosal fluids for early fish welfare monitoring.