This talk will present measurements of interactions between nanoparticles and confining surfaces with and without adsorbed polyelectrolytes and proteins. Specifically, results will be presented for evanescent wave scattering and video microscopy measurements of 50, 100, and 250nm 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 adsorbed polyelectrolyte multilayers and proteins at physiological ionic strengths. Polyelectrolyte layers were adsorbed in a layer-by-layer fashion on the particle and confining surfaces to control layer thicknesses and the range of macromolecular repulsion within several nanometers. In contrast, bovine serum albumin was adsorbed to give adsorbed monolayers with a uniform range of repulsion. Equilibrium analyses of single and ensemble particle height distributions normal to the confining walls produce electrostatic and macromolecular potentials in excellent agreement with theoretical predictions. These results demonstrate a consistent interpretation of nanoparticle interactions in confined geometries. Ongoing work is extending the methods presented here to measure specific interactions between biomacromolecules attached and oriented to nanoparticle and wall surfaces.