Polymorphism of stable collagen fibrils

Area of Science:

• Biophysics
• Materials Science
• Biomolecular Engineering

Background:

• Collagen fibrils are essential for tissue mechanical integrity.
• Fibril radius varies significantly based on experimental and anatomical context.
• Understanding collagen fibril self-assembly is key to tissue engineering and regenerative medicine.

Purpose of the Study:

• To explore thermodynamically stable collagen fibril configurations.
• To identify key parameters governing fibril radius and surface twist.
• To model the relationship between material properties and fibril morphology.

Main Methods:

• Utilized a liquid crystal model with a double-twist director field.
• Employed a numerical relaxation method for simulations.
• Analyzed the influence of elastic constants (k24/K22) and reduced surface tension ([small gamma, Greek, tilde]).

Main Results:

• Two dimensionless parameters dictate scaled fibril radius and surface twist.
• Collagen fibrils are stable over cholesteric phases when reduced surface tension is low ([small gamma, Greek, tilde] ⪅ 0.2).
• A maximal equilibrium surface twist of 0.33 rad (19°) was identified.

Conclusions:

• The model explains the narrow radius distribution of corneal collagen fibrils via large surface twist.
• Small surface twist is necessary for tendon fibril stability despite radius variations.
• Thermodynamic stability and morphology of collagen fibrils are predictable through material properties.