A novel portable label-free electrochemical immunosensor for ultrasensitive detection of Aeromonas salmonicida in aquaculture seawater

Infectious diseases caused by Aeromonas salmonicida (A. salmonicida) have a huge impact and produce significant losses in aquaculture and fish farming. Fish pathogen early detection is a critical step for the rapid identification and prevention of these problems. This work presents a novel portable label-free ultrasensitive electrochemical immunosensor for A. salmonicida detection in seawater. It consists of a fluidic integrated electrochemical-cell-chip (ECC) with independent chambers enclosing three electrochemical cells (ECs). Anti-A. salmonicida (AbSalm) antibodies were covalently attached to the gold surface of the microfabricated electrodes and were used for the sensitive detection of A. salmonicida. The antibody-antigen immunoreaction was studied by enzyme-linked immunosorbent assay (ELISA), and the surface functionalization was characterized by using quartz crystal microbalance (QCM), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The performance of the developed immunosensor, in terms of sensitivity, repeatability, and specificity, was also studied. The linear working range varied between 1 and 107 CFU mL-1, with a limit of detection (LOD) as low as 1 CFU mL-1. The suitability of the immunosensor for real sample detection was successfully demonstrated via recovery studies performed in spiked seawater samples. The proposed technology supports the use of low-cost and portable instrumentation that concedes the ultrasensitive, simple, and fast quantification of the A. salmonicida. To the best of our knowledge, this is the first portable sensing system for the detection of A. salmonicida in seawater samples, which provides a promising online monitoring platform for the detection of this bacterium in aquaculture facilities.