(755d) Diffusing Nanoparticle Measurements of Biomolecular Interactions

This talk will present measurements of interactions between nanoparticles and confining surfaces with and without adsorbed carbohydrates and proteins. Results will be presented for evanescent wave scattering and video microscopy measurements of gold nanoparticles confined in submicron gaps between parallel walls. Initially, measurements were performed for bare nanoparticles stabilized via long range electrostatic repulsion in low ionic strength media. After establishing the behavior of bare particles at low ionic strengths, measurements were performed for particles stabilized by proteins and carbohydrates at physiological ionic strengths. Proteins and carbohydrates were adsorbed on the particle and confining surfaces to give adsorbed monolayers with a uniform range of repulsion and non-specific protein interactions. Further research involving weak specific interactions utilizing adsorbed proteins interacting with various carbohydrates will be presented. These results demonstrate the sensitivity of this technique to potential energy profiles relating to a range of protein dissociation constants. Experiments were also performed with various sizes of nanoparticles to control the number of protein-carbohydrate interactions. The research presented shows a consistent interpretation of nanoparticle and biomolecular interactions in confined geometries. Ongoing work is extending the methods presented here to measure stronger specific interactions and interactions with biomolecules attached and oriented to nanoparticle and wall surfaces.