title: Determination of the magneto-optical relaxation of magnetic nanoparticles as a homogeneous immunoassay.
abstract: The interaction between human eotaxin (hEotaxin) and its polyclonal antibody anti-human eotaxin (anti-hEotaxin) was investigated by means of a novel liquid-phase immunoassay using the magneto-optical relaxation of ferrofluids. The binding quality as well as kinetic properties of the binding partners was determined using specifically binding magnetic probes. For this purpose, magnetic nanoparticles (MNP; DDM128N, Meito Sangyo, Japan) were initially functionalized with streptavidin. The biotin-nylated antibody was conjugated with streptavidin-MNP applying the streptavidin-biotin binding system. Binding reactions were detected by measuring the relaxation of the optical birefringence signal occurring when a pulsed magnetic field is applied to the ferrofluid. The addition of hEotaxin to anti-hEotaxin conjugated MNP in different amounts yielded an enlargement of the mean relaxation time due to the formation of MNP aggregates. In order to express the observed increase of the particles' effective diameter in terms of elementary kinetic processes between antigen and antibody, a kinetic model was introduced. Here, the binding reactions are described by a process of stepwise polymerization. The obtained results were compared with data received from surface plasmon resonance biosensor analysis, a standard tool for biomolecular interaction analysis.
authors.affiliation: Institute of Pharmacy, Department of Biopharmaceutics and Pharmaceutical Technology, University of Greifswald, Friedrich-Ludwig-Jahn-Strasse 17, 17487 Greifswald, Germany.
authors.forename: Konstanze
authors.initials: K
authors.lastname: Aurich
authors.forename: Stefan
authors.initials: S
authors.lastname: Nagel
authors.forename: Gunnar
authors.initials: G
authors.lastname: Glöckl
authors.forename: Werner
authors.initials: W
authors.lastname: Weitschies
mesh_terms: D000906:Antibodies / Q000276:immunology; D000937:Antigen-Antibody Reactions; D001710:Biotin / Q000737:chemistry; D054413:Chemokine CCL11; D019742:Chemokines, CC / Q000276:immunology; D006801:Humans; D007118:Immunoassay; D008280:Magnetics; D053758:Nanoparticles / Q000737:chemistry*; D055095:Optics and Photonics; D019809:Streptavidin / Q000737:chemistry
chemical_list: D000906:Antibodies; C515456:CCL11 protein, human; D054413:Chemokine CCL11; D019742:Chemokines, CC; D001710:Biotin; D019809:Streptavidin