Antibody binding to antigenic peptide conjugated gold nanoparticles is strongly dependent on antigen density

A 13 nm gold nanoparticle (G13) coated with varying densities of His₆ peptide (as a model antigen) was used to study how antigen presentation affects antibody binding, assessed by dynamic light scattering and fluorescence-quenching assays. We found that antigen density and deflection angle strongly influence antibody binding to the G13-His₆ conjugates, yielding over a 120-fold increase in apparent affinity as the His₆ density increases from 2% to 10% (His 6 deflection angle reduces from 37 o to 16 o).