Large changes in the hydration and mechanical properties of dendritic phytoglycogen nanoparticles with chemical modification

Phytoglycogen is a glucose-based polysaccharide nanoparticle with a highly branched, dendritic architecture. We used ellipsometry at different relative humidities (RH) to compare the equilibrium RH-driven swelling of ultrathin films of native and chemically modified phytoglycogen, as well as dextran and hyaluronic acid. Our analysis allowed us to compare the hydration force decay length λ and bulk modulus K of the films. We also used attenuated total reflection infrared spectroscopy to investigate the hydrogen bond structure of the hydration water in the polysaccharide films. By combining ellipsometry and infrared spectroscopy, we find that structuring of the hydration water hydrogen bond network correlates with both λ and K.These measurements provide insight into the relationship between the hydration water structure and mechanical properties of polysaccharides, suggesting that a more ordered water hydrogen bond network leads to a shorter λ and larger K. Significantly, we find that chemical modification of phytoglycogen dramatically alters its hydration and mechanical properties, highlighting opportunities to tailor its properties for different applications.