title: A new approach for bioassays based on frequency- and time-domain measurements of magnetic nanoparticles.
abstract: We demonstrate a one-step wash-free bioassay measurement system capable of tracking biochemical binding events. Our approach combines the high resolution of frequency- and high speed of time-domain measurements in a single device in combination with a fast one-step bioassay. The one-step nature of our magnetic nanoparticle (MNP) based assay reduces the time between sample extraction and quantitative results while mitigating the risks of contamination related to washing steps. Our method also enables tracking of binding events, providing the possibility of, for example, investigation of how chemical/biological environments affect the rate of a binding process or study of the action of certain drugs. We detect specific biological binding events occurring on the surfaces of fluid-suspended MNPs that modify their magnetic relaxation behavior. Herein, we extrapolate a modest sensitivity to analyte of 100 ng/ml with the present setup using our rapid one-step bioassay. More importantly, we determine the size-distributions of the MNP systems with theoretical fits to our data obtained from the two complementary measurement modalities and demonstrate quantitative agreement between them.
authors.affiliation: Department of Microtechnology and Nanoscience-MC2, Chalmers University of Technology, Göteborg, Sweden. fredrik.oisjoen@chalmers.se
authors.forename: Fredrik
authors.initials: F
authors.lastname: Oisjöen
authors.forename: Justin F
authors.initials: JF
authors.lastname: Schneiderman
authors.forename: Andrea Prieto
authors.initials: AP
authors.lastname: Astalan
authors.forename: Alexey
authors.initials: A
authors.lastname: Kalabukhov
authors.forename: Christer
authors.initials: C
authors.lastname: Johansson
authors.forename: Dag
authors.initials: D
authors.lastname: Winkler
mesh_terms: D001681:Biological Assay / Q000295:instrumentation*; D015374:Biosensing Techniques / Q000295:instrumentation; D004867:Equipment Design; D019544:Equipment Failure Analysis; D018189:Immunomagnetic Separation / Q000295:instrumentation*; D008280:Magnetics / Q000295:instrumentation*; D053758:Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity