Protein−Ligand Interactions at Poly(amidoamine) Dendrimer Monolayers on Gold

Abstract

Avidin−biotin interactions as a typical protein−ligand model were investigated on the monolayers of a fourth-generation poly(amidoamine) dendrimer that were constructed on the self-assembled monolayers (SAMs) of 11-mercaptoundecanoic acid (MUA) on gold. Surface plasmon resonance (SPR) spectroscopic analysis revealed a resonance angle shift of 0.34° ± 0.03° for the formation of dendrimer monolayers on reactive SAMs, which indicates that about 89% of the gold surface is covered with dendrimer molecules. The dendrimer monolayers were functionalized with biotin, and the efficacy of dendrimer monolayers as a biomolecular interface was evaluated in terms of the surface density of biotin ligands and the avidin binding level. For comparisons, the mixed SAMs and polymeric layers of poly-l-lysine (PLL) on MUA SAMs were prepared and examined by a similar procedure. The specific binding of avidin to the biotinylated dendrimer monolayers approached a surface density of 5.0 ± 0.2 ng·mm-2, which corresponds to about 88%...