title: Quantitative interpretation of gold nanoparticle-based bioassays designed for detection of immunocomplex formation.
abstract: The authors present in this paper how the extended Mie theory can be used to translate not only end-point data but also temporal variations of extinction peak-position changes, Deltalambda(peak)(t), into absolute mass uptake, Gamma(t), upon biomacromolecule binding to localized surface plasmon resonance (SPR) active nanoparticles (NPs). The theoretical analysis is applied on a novel sensor template composed of a three-layer surface architecture based on (i) a self-assembled monolayer of HS(CH(2))(15)COOH, (ii) a 1:1 mixture of biotinylated and pure poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG), and (iii) NeutrAvidin. Assisted by independent estimations of the thickness of the three-layer architecture using quartz crystal microbalance with dissipation (QCM-D) monitoring, excellent agreement with parallel mass-uptake estimations using planar SPR is obtained. Furthermore, unspecific binding of serum to PLL-g-PEG was shown to be below the detection limit, making the surface architecture ideally suited for label-free detection of immunoreactions. To ensure that the immunocomplex formation occurred within the limited sensing depth (approximately 10 nm) of the NPs, a compact model system composed of a biotinylated human recombinant single-chain antibody fragment (slashed circle approximately 2 nm) directed against cholera toxin was selected. By tracking changes in the centroid (center of mass) of the extinction peak, rather than the actual peak position, signal-to-noise levels and long-term stability upon cholera toxin detection are demonstrated to be competitive with results obtained using conventional SPR and state-of-the-art QCM-D data.
authors.affiliation: Division of Solid State Physics, Lund University, SE-22100 Lund, Sweden.
authors.forename: Ye
authors.initials: Y
authors.lastname: Zhou
authors.forename: Hongxing
authors.initials: H
authors.lastname: Xu
authors.forename: Andreas B
authors.initials: AB
authors.lastname: Dahlin
authors.forename: Jacob
authors.initials: J
authors.lastname: Vallkil
authors.forename: Carl A K
authors.initials: CA
authors.lastname: Borrebaeck
authors.forename: Christer
authors.initials: C
authors.lastname: Wingren
authors.forename: Bo
authors.initials: B
authors.lastname: Liedberg
authors.forename: Fredrik
authors.initials: F
authors.lastname: Höök