Preparation of SiO₂/Polymethyl Methacrylate/Fe₃O₄ Nanoparticles and Its Application in Detecting E. coli O157:H7 Using Chemiluminescent Immunological Method

This paper described that Fe₃O₄ nanoparticles were encapsulated with methyl methacrylate (MMA) using linolenic acid (LA) as a crosslinking agent, after which the resulting polymethyl methacrylate (PMMA) embed Fe₃O₄ nanoparticles (PMMA/Fe₃O₄) were coated with silica, forming SiO₂/(PMMA/Fe₃O₄) core–shell structure particles. Then these magnetic nanoparticles (MNPs) were applied in the developed system of chemiluminescent magnetic enzyme-linked immunoassay. E. coli O157:H7 was sandwiched between rabbits anti-E. coli O157:H7 polyclonal antibody-coated magnetite nanoparticles (immunomagnetic nanoparticles or IMNPs) and mouse anti-E. coli O157:H7 monoclonal antibody (E. coli O157-McAb). Commercial alkaline phosphatase conjugated horse anti-mouse immunoglobulin (ALP-Ab) was used to bond with the monoclonal antibody, finally the chemiluminescent signals were detected by adding 3-(2′-spiroadamantane)-4-methoxy-4-(3″-phosphoryloxy)phenyl-1,2-dioxetane (AMPPD) which was the substrate reagent of ALP. The specificity and sensitivity of this system for detecting E. coli O157:H7 were researched. The results indicated that this method was of good specificity when using E. coli Top 10F′ and Vibrio cholera as negative controls. The detection limit was 10³ cells mL⁻¹ when the antigen solution was 1 mL, and the procedure duration was about 3 h.