title: Blu-ray optomagnetic measurement based competitive immunoassay for Salmonella detection.
abstract: A turn-on competitive immunoassay using a low-cost Blu-ray optomagnetic setup and two differently sized magnetic particles (micron-sized particles acting as capture particles and nano-sized particles acting as detection particles) is here presented. For Salmonella detection, a limit of detection of 8×10(4)CFU/mL is achieved within a total assay time of 3h. The combination of a competitive strategy and an optomagnetic setup not only enables a turn-on read-out format, but also results in a sensitivity limit about a factor of 20 times lower than of volumetric magnetic stray field detection device based immunoassays. The improvement of sensitivity is enabled by the formation of immuno-magnetic aggregates providing steric hindrance protecting the interior binding sites from interaction with the magnetic nanoparticle labels. The formation of immuno-magnetic aggregates is confirmed by fluorescence microscopy. The system exhibits no visible cross-reaction with other common pathogenic bacteria, even at concentrations as high as 10(7)CFU/mL. Furthermore, we present results when using the setup for a qualitative and homogeneous biplex immunoassay of Escherichia coli and Salmonella typhimurium.
authors.affiliation: Department of Engineering Sciences, Uppsala University, Box 534, SE-751 21 Uppsala, Sweden.
authors.forename: Bo
authors.initials: B
authors.lastname: Tian
authors.affiliation: Department of Engineering Sciences, Uppsala University, Box 534, SE-751 21 Uppsala, Sweden.
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Bejhed
authors.affiliation: Department of Engineering Sciences, Uppsala University, Box 534, SE-751 21 Uppsala, Sweden.
authors.forename: Peter
authors.initials: P
authors.lastname: Svedlindh
authors.affiliation: Department of Engineering Sciences, Uppsala University, Box 534, SE-751 21 Uppsala, Sweden. Electronic address: mattias.stromberg@angstrom.uu.se.
authors.forename: Mattias
authors.initials: M
authors.lastname: Strömberg
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D016251:CD-ROM; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007118:Immunoassay / Q000295:instrumentation*; D018189:Immunomagnetic Separation / Q000295:instrumentation*; D008280:Magnetics / Q000295:instrumentation; D055096:Optical Devices; D015203:Reproducibility of Results; D012475:Salmonella / Q000276:immunology* / Q000302:isolation & purification*; D012680:Sensitivity and Specificity
keywords: Biosensors; Immunoassays; Magnetic particles; Magneto-optics