Combining Colloidal Probe Atomic Force and Reflection Interference Contrast Microscopy to Study the Compressive Mechanics of Hyaluronan Brushes

摘要

We describe a method that combines colloidal probe atomicnforce microscopy (AFM) and reflection interference contrast microscopyn(RICM) to characterize the mechanical properties of thin and solvatednpolymer films. When analyzing polymer films, a fundamental problem inncolloidal probe AFM experiments is to determine the distance at closestnapproach between the probe and the substrate on which the film isndeposited. By combining AFM and RICM in situ, forces and absolute distancesncan be measured simultaneously. Using the combined setup, wenquantify the compressive mechanics of films of the polysaccharide hyaluronan that is end-grafted to a supported lipid bilayer. Thenexperimental data, and comparison with polymer theory, show that hyaluronan films are well-described as elastic, very soft and highlynsolvated polymer brushes. The data on these well-defined films should be a useful reference for the investigation of the more complexnhyaluronan-rich coats that surround many living cells.