One novel composite nano-particles membrane modified amperometric immunosensor for Escherichia coli in polluted waters

A novel amperometric immunoassay for identification of Escherichia coli (E.coli) in a matrix containing zirconium dioxide nanoparticles (ZrO₂) was described. Firstly, the antibody of E.coli (anti E.coli) was immobilized on a glassy carbon electrode (GCE) modified with carbon nanotubes (CNTs) using ZrO₂ nanoparticles, colloidal gold (Au) and poly-Lysine (pLL) composite membrane (ZrO₂-Au-pLL-anti-E.coli) aiming to maintain the antibody´s bioactivity. Then one novel sebacato-bridged Co(□) complex Co(suc)(bpy)(H₂O)₂ (referred to as CoL, suc=succinic acid; bpy=2,2´-bipyridine) was adsorbed onto the surface of ZrO₂-Au-pLL-anti-E.coli composite membrane, thus the immunosensor (GCE|CNTs|ZrO₂-Au-pLL-anti-E.coli|CoL) for determination of E.coli was constructed based on one step immunoreaction using cyclic voltammetry (CV) method. CoL can be employed as an electron transfer mediator for catalytic activity detection of H₂O₂. After the immunosensor was incubated with E.coli solution at room temperature for 20 min, the electron transfer access of CoL to H₂O₂ was partly inhibited, which leads to a linear decrease of the catalytic efficiency to H₂O₂. The immunosensor was employed to determine E.coli in samples and the results were consistent to the tradition enzyme-linked immunosorbent assays (ELISA) method. The proposed ampero metric immunosensor was sensitive, quick and disposable, which was suitable for determination of E.coli in polluted waters for public health and environmental protection.