title: Colloidal Au-enhanced surface plasmon resonance immunosensing.
abstract: Surface plasmon resonance (SPR) biosensing using colloidal Au enhancement is reported. Immobilization of approximately 11-nm-diameter colloidal Au to an evaporated Au film results in a large shift in plasmon angle, a broadened plasmon resonance, and an increase in minimum reflectance. The incorporation of colloidal Au into SPR biosensing results in increased SPR sensitivity to protein-protein interactions when a Au film-immobilized antibody and an antigen-colloidal Au conjugate comprise the binding pair. A highly specific particle-enhanced analogue of a sandwich immunoassay is also demonstrated by complexing the Au particle to a secondary antibody. A tremendous signal amplification is observed, as addition of the antibody-Au colloid conjugate results in a 25-fold larger signal than that due to addition of a free antibody solution that is 6 orders of magnitude more concentrated. Picomolar detection of human immunoglobulin G has been realized using particle enhancement, with the theoretical limits for the technique being much lower. Finally, a quasi-linear relationship between particle coverage and plasmon angle shift is presented, thereby providing for a direct correlation between plasmon shift and solution antigen concentration. Together, these results represent significant advances in the generality and sensitivity of SPR as it is applied to biosensing.
authors.affiliation: Department of Chemistry, Pennsylvania State University, University Park 16802, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Lyon
authors.forename: M D
authors.initials: MD
authors.lastname: Musick
authors.forename: M J
authors.initials: MJ
authors.lastname: Natan
mesh_terms: D003102:Colloids; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007074:Immunoglobulin G / Q000032:analysis*; D020349:Surface Plasmon Resonance
chemical_list: D003102:Colloids; D007074:Immunoglobulin G