Model System for Investigating Glycocalyx-Relevant Hydration Phenomena

An interface-sensitive spectroscopic hydration metrology has been established to resolve and stabilize interface associated water states on thin films. This technique has been tested using a specially adapted artificial glycocalyx-inspired polyelectrolyte multilayer (PEM) platform assembled by the layer-by-layer technique from chitosan and glycosaminoglycans with systematically varied sulfation. For this purpose, polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) was combined with a newly developed temperature- and humidity-controlled measurement chamber, ensuring the reproducible characterization of hydration states in thin films. For the first time, different water structures associated with the interface─nonfreezing, intermediate, and free water─were detected and quantified with such a high degree of precision and under such controlled conditions on glycocalyx-like surfaces. In consideration of these findings, it was proposed that protein adsorption to the model depends on the exclusion of free water and sulfation depending on electrostatic interactions, thereby explaining the increased adsorption on highly sulfated and stable hydrated PEMs. The glycocalyx-inspired system establishes a fundamental platform for investigating hydration-mediated protein-surface interactions in complex biological media. The demonstrated technique can be transferred not only to other PEMs but also to thin films in general including polymer brushes and zwitterionic materials. This transfer is applicable in the fields of antifouling, blood-contacting materials, and drug delivery systems.