  Chitosan and chitin are promising biopolymers used in many areas including
biomedical applications, such as tissue engineering and viscosupplementation.
Chitosan shares similar properties with hyaluronan, a natural component of
synovial fluid, making it a good candidate for joint disease treatment. The
structural and energetic consequences of intermolecular interactions are
crucial for understanding the biolubrication phenomenon and other important
biomedical features. However, the properties of biopolymers, including their
complexation abilities, are influenced by the nature of the aqueous medium with
which they interact. In this study, we employed molecular dynamics simulations
to describe the effect of pH and the presence of sodium and calcium cations on
the stability of molecular complexes formed by collagen type II with chitin and
chitosan oligosaccharides. Based on Gibbs free energy of binding, all
considered complexes are thermodynamically stable over the entire pH range. The
affinity between chitosan oligosaccharide and collagen is highly influenced by
pH, while oligomeric chitin shows no pH-dependent effect on the stability of
molecular assemblies with collagen. On the other hand, the presence of sodium
and calcium cations has a negligible effect on the affinity of chitin and
chitosan for collagen.
