Electrochemical bioassay based on l-lysine-modified magnetic nanoparticles for Escherichia coli detection: Descriptive results and comparison with other commercial magnetic beads

This paper describes the synthesis and biofunctionalization of magnetic nanoparticles (MNPs) of about 10 nm obtained by the coprecipitation method under alkaline conditions. These homemade nanoparticles were conveniently modified with l-lysine and glutaraldehyde and used as solid support for the immunochemical determination of Escherichia coli. Biofunctionalized MNPs were characterized by X-ray diffraction (XRD), Fourier-Transform Infrared spectroscopy (FTIR), Atomic Force Microscopy (AFM), and thermogravimetric analysis. Electrochemical detection was based on a sandwich Enzyme-Linked Immuno Magnetic Electrochemical (ELIME) method using a primary antibody (capture antibody, Ab1) and an HRP-labeled antibody (secondary, Ab-HRP). The enzymatic by-product was measured by constant potential amperometry.