Binding of Proteins to Surface Plasmon Resonance Biochips Functionalized with Native and Size-Reduced Phytoglycogen Nanoparticles

Phytoglycogen is a highly branched, compact, natural polymer of glucose produced by sweet corn. Its softness, porosity and mechanical integrity, as well as nontoxicity and biodegradability, make it ideal for applications involving the human body. Many of these applications rely on binding of bioactive molecules to phytoglycogen nanoparticles. We probe intermolecular binding affinities and kinetics using Surface Plasmon Resonance (SPR) imaging. We have successfully produced SPR biochips functionalized with both native and size-reduced phytoglycogen using a self-assembled monolayer of 4-mercaptophenylboronic acid as an intermediate linker between the gold substrate and phytoglycogen. This has allowed us to determine the association constant between concanavalin A (conA) and both native and size-reduced phytoglycogen by fitting the SPR data to the Langmuir adsorption model. We used infrared spectroscopy to monitor the amide bands of the bound conA molecules, confirming that conA maintained a significant portion of its native beta-sheet content and suggesting that binding of conA to phytoglycogen does not significantly reduce its bioactivity.