title: Modeling and development of a biosensor based on optical relaxation measurements of hybrid nanoparticles.
abstract: We present a new approach for homogeneous real-time immunodiagnostics (denoted as "PlasMag") that can be directly carried out in sample solutions such as serum, thus promising to circumvent the need of sample preparation. It relies on highly sensitive plasmon-optical detection of the relaxation dynamics of magnetic nanoparticles immersed in the sample solution, which changes when target molecules bind to the surfaces of the nanoparticles due to the increase in their hydrodynamic radii. This method requires hybrid nanoparticles that combine both magnetic and optical anisotropic properties. Our model calculations show that core-shell nanorods with a cobalt core diameter of 6 nm, a cobalt core length of 80 nm, and a gold shell thickness of 5 nm are ideally suited as nanoprobes. On the one hand, the spectral position of the longitudinal plasmon resonance of such nanoprobes lies in the near-infrared, where the optical absorption in serum is minimal. On the other hand, the expected change in their relaxation properties on analyte binding is maximal for rotating magnetic fields as excitation in the lower kHz regime. In order to achieve high alignment ratios of the nanoprobes, the strength of the magnetic field should be around 5 mT. While realistic distributions of the nanoprobe properties result in a decrease of their mean optical extinction, the actual relaxation signal change on analyte binding is largely unaffected. These model calculations are supported by measurements on plain cobalt nanorod dispersions, which are the base component of the aspired core-shell nanoprobes currently under development.
authors.affiliation: Molecular Diagnostics, AIT Austrian Institute of Technology, Vienna, Austria. stefan.schrittwieser.fl@ait.ac.at
authors.forename: Stefan
authors.initials: S
authors.lastname: Schrittwieser
authors.forename: Frank
authors.initials: F
authors.lastname: Ludwig
authors.forename: Jan
authors.initials: J
authors.lastname: Dieckhoff
authors.forename: Katerina
authors.initials: K
authors.lastname: Soulantica
authors.forename: Guillaume
authors.initials: G
authors.lastname: Viau
authors.forename: Lise-Marie
authors.initials: LM
authors.lastname: Lacroix
authors.forename: Sergio Mozo
authors.initials: SM
authors.lastname: Lentijo
authors.forename: Rym
authors.initials: R
authors.lastname: Boubekri
authors.forename: Jérôme
authors.initials: J
authors.lastname: Maynadié
authors.forename: Andreas
authors.initials: A
authors.lastname: Huetten
authors.forename: Hubert
authors.initials: H
authors.lastname: Brueckl
authors.forename: Joerg
authors.initials: J
authors.lastname: Schotter
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007118:Immunoassay / Q000295:instrumentation*; D018189:Immunomagnetic Separation / Q000295:instrumentation*; D058185:Magnetite Nanoparticles / Q000737:chemistry*
chemical_list: D058185:Magnetite Nanoparticles