Hepatocyte culture on carbohydrate-modified star polyethylene oxide hydrogels

We describe the synthesis and in vitro biological characterization of a new class of carbohydrate-modified hydrogels based on radiation-cross-linked star polyethylene oxide (PEG). Hydrogels were synthesized from either of two types of PEO star molecules in order to vary the terminal hydroxyl content of the gels while keeping other gel properties such as molecular weight between cross-links and water content constant. The resulting gels were covalently modified with monosaccharide ligands and the behaviour of primary rat hepatocytes on the modified gels was evaluated under culture conditions. Hepatocytes exhibited a sugar-specific adhesion to the modified gels, adhering to gels bearing galactose but not glucose. Cell spreading was observed on both types of galactose-modified PEO star gels; moreover, the gels supported long-term (6 d) culture and differentiated function of primary hepatocytes. Further, on comparing the cell spreading behaviour observed on the PEO star gels with that reported previously for galactose-modified polyacrylamide, we find that our gels elicit spreading at ligand concentrations lower by an order of magnitude. A simple mechanistic analysis indicates that this enhanced ability of PEO star gels to support spreading of primary hepatocytes on low concentrations of immobilized galactose derives from freedom of the immobilized ligands to come within sufficiently close proximity to mimic a high-affinity branched oligosaccharide.