Immunomagnetic nanoparticles based on a hydrophilic polymer coating for sensitive detection of Salmonella in raw milk by polymerase chain reaction

In this study, hydrophilic polymer dextran and superhydrophilic polymer PMPC coated iron oxide immunomagnetic nanoparticles were prepared for rapid capture and detection of Salmonella. It was found that the colloidal stability of magnetic iron oxide nanoparticles in aqueous solution imposed a significant influence on the Salmonella capture efficiency. The superhydrophilic poly(2-methacryloyloxyethyl phosphorylcholine (PMPC) coating could increase the capture performance of immunomagnetic nanoparticles effectively. At the Salmonella concentration of 10(1)-10(4) cfu mL(-1), the dextran coated iron oxide nanoparticles obtained by a coprecipitation method showed moderate capture efficiency of about 43-48%. An iron oxide cluster obtained by a solvothermal route obviously impeded the capture behavior, causing a lower Salmonella capture efficiency of about 25% and relatively higher false-positive result. Superior capture efficiency was achieved by PHEMA/PMPC coated immunomagnetic particles. The PHEMA/PMPC coated immunomagnetic particles yielded higher capture efficiency than that of the commercial Dynal immunomagnetic particles in the experimentally contaminated milk. After 5 hours culture in peptone water, the PCR detection limit of PHEMA/PMPC coated immunomagnetic nanoparticles was 10(1) cfu mL(-1), one order higher than that of the commercial Dynal IMB under the same conditions. The superhydrophilic PMPC coated iron oxide nanoparticles show great promise in highly sensitive detection of pathogenic bacteria.