MOLECULAR DYNAMICS SIMULATIONS OF THE AFFINITY OF CHITIN AND CHITOSAN FOR COLLAGEN: THE EFFECT OF pH AND THE PRESENCE OF SODIUM AND CALCIUM CATIONS

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.

Effect of Nanohydroxyapatite on Silk Fibroin–Chitosan Interactions—Molecular Dynamics Study

“…These properties can be manifested in complex molecular systems. Nevertheless, similar calculations performed in previous studies [63] have shown that even oligomeric chitosan chains exhibit polyelectrolytic features. Since polyelectrolytes contain many ionic and polar groups, they are capable of forming various intermolecular contacts.…”

“…Despite these disparities, both values are remarkably high. Notably, the binding energies, calculated through similar procedures for chitosancollagen complexes as reported in our previous studies [61,63], did not exceed 850 kJ/mol. This suggests a significantly lower mutual affinity between chitosan and collagen compared to chitosan-fibroin systems.…”

“…While both biomolecules become positively charged through protonation, the formation of stable complexes is possible due to the presence of oppositely charged ions that neutralize the positive charge. Our previous studies [63] have demonstrated similar behavior in the case of collagen-chitosan systems. Importantly, both chitosan and proteins, such as collagen and fibroin, exhibit polyelectrolytic properties [105][106][107], leading to charge migration within the polymer chain and fluctuations in charge density within the biomolecule.…”

“…All molecular dynamics computations were carried out using an YASARA software [78,79], a comprehensive and versatile tool for modeling biopolymer complexes, including polysaccharide/peptide systems [61][62][63][64][80][81][82]. The structure of the chitosan was taken from PubChem (PubChem CID: 129662530) and modified to obtain polymer of total mass of 200 kDa (1250 monomer units).…”

“…Importantly, the direct evidence of the relationships between the strength and mechanical properties of intermolecular interactions was demonstrated by studies that explored experimental analysis with molecular dynamics computations [59,60]. Our previous research employed molecular dynamics simulations to explore complexes of chitosan/chitin with collagen [61][62][63] and hyaluronan [64]. Understanding these interactions is crucial for developing strategies for cartilage regeneration [65].…”