Rheological properties and solvent structure of polysaccharide hydrogels studied by molecular dynamics simulations

One important class of hydrogels based on natural polymers is the Glycosaminoglycan (GAG)-based hydrogels. In hydrogels biomaterial science, the mathematical modeling and computer simulation plays a complementary interpretative role in deciphering the complex physical/chemical and biological properties of this class of substances. Aim: the molecular modeling studies presented here aimed the information gathering regarding the particular molecular interactions responsible for rheological properties of this class of biomaterials. Methods: the methods included molecular dynamics simulations in the NPT ensemble for polysaccharidic matrices, radial function analysis for the solvent and viscosity calculations using periodic strain non-equilibrium molecular dynamics. All this methods were applied to models of 100%, 66% and 33% of maximum hydration compared to pure solvent simulations as control. Results and conclusions: decreasing the water content of the polymer matrix drastically affects the conformational flexibility of the polymer chains, the solvent percolation and viscosity coefficient of the biomaterials studied. The obtained viscosity coefficients were: H2O = 0.982×10-3 kg/(ms); 100% = 1.520×10-3 kg/(ms); 66% = 1.862×10-3 kg/(ms); 33% = 2.602×10-3 kg/(ms). The findings are useful for polysaccharidic hydrogel materials science as the rheological and solvent structuralisation can dramatically influence the physical stability of eventual macromolecular bioactive agents (e.g. therapeutic proteins) when they are loaded into such matrices for controlled delivery, especially during the storage period when the material is kept in lyophilised conditions.