Plant heteropolysaccharides and their bioadhesion to animal glycocalyx visualized at the nanoscale

The plant-derived biopolymer pectin has been explored as sealant in lung surgery. Interpenetration of pectin's heteropolysaccharide chains with sugar-chains on components of the mesothelial glycocalyx is thought to mediate adhesion. To visualize a potential adhesion complex, we first establish a method to preserve pectin ultrastructure by limiting hydration during sample preparation for electron microscopy. Depending on actual hydration states and pectic domains selected we find distinct morphologies: Citrus pectic polysaccharides, combining both, smooth homogalacturonan and hairy rhamnogalacturonan domains, form a loose network of thin filaments. Rhamnogalacturonan and xylogalacturonan domains from soy show a denser mesh, while pectic galactan from potato or pectic arabinan from sugar beet display more globular aspects. As proof of concept, we finally apply the filamentous lemon pectin to the surface of murine lung in a surgical setting. Ultrastructural visualization of the sealant-tissue assembly shows tight association between the carbohydrate fibers, possibly driven by polymer-typical chain interactions.