Molecular dynamics simulations of the affinity of chitin and chitosan for collagen: the effect of pH and the presence of sodium and calcium cations

TL;DR

This study uses molecular dynamics simulations to explore how pH and cations affect the stability of collagen complexes with chitin and chitosan, revealing pH-dependent affinity variations and negligible cation effects.

Contribution

It provides new insights into the thermodynamic stability of collagen-biopolymer complexes under different pH and ionic conditions using molecular dynamics simulations.

Findings

All complexes are thermodynamically stable across pH range.

Chitosan affinity with collagen is pH-dependent.

Cations have negligible effect on complex stability.

Abstract

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.