Byoung Yun Kim

Binding Evaluation of Targeted Microbubbles with Biotin?Avidin Interaction by Surface Plasmon Resonance Biosensor

Targeted microbubbles for ultrasound imaging were examined with an avidin-modified gold surface of a surface plasmon resonance (SPR) biosensor. Contrast media of ultrasound (US) imaging were fabricated with dispersions of biotinylated gases (microbubbles) in an aqueous medium and the binding interaction of a targeted microbubble contrast agent was characterized by the refractive index change of the adsorbed layers in the SPR biosensor. The shells of the microbubbles were consisted of a gas-filled layer of lipids and polypeptides. Avidin–biotin interaction as a typical protein–ligand model was investigated on biotinylated polypeptide lipid microbubbles that were functionalized with biotin by directly grafting them to poly(succinimide) (PSI). The targeted microbubbles were below 7 µm (95%) and their mean diameter was 2.5 µm. The affinity constant (KA) of the biotinylated polypeptide lipid-microbubbles from the SPR data (KA=9.46 g-1 L) was about 10 times greater than that of polypeptide lipid microbubbles (KA=1.00 g-1 L). The SPR biosensor may help in the prediction of the in vivo behavior of targeted microbubbles (ultrasound contrast agent) in a flow system and in the design of successful target preparation.

SURFACE FABRICATION OF BIOTINYLATED POLYPEPTIDE MULTI-LAYER DESIGNED FOR SURFACE PLASMON RESONANCE SENSING

The novel modification of gold surfaces with a biotinylated polypeptide multilayer formed by nonspecific electrostatic adsorption was designed for the SPR sensing platform. The multilayer of polypeptides (poly-L-lysine and poly(aspartic acid)) was prepared onto a negatively charged self-assembled monolayer of 11-mercaptoundecanoic acid (MUA) on gold film. The polypeptide multilayer was functionalized with biotin by directly grafting to poly(succinimide) (PSI). The specific binding of avidin to the biotinylated polypeptide multilayer (DS 2.7%) resulted in a shift in the refractive index of 0.003±9×10-4 with a surface density of 2.9 ng/mm2. This multilayer surface was found to provide a simple and effective method for the SPR sensing.