Mineralization generates megapascal contractile stresses in collagen fibrils

Area of Science:

• Biomaterials science
• Biomineralization
• Materials science

Background:

• Bone is a hybrid material composed of collagen fibrils mineralized with carbonated hydroxyapatite.
• Collagen's ability to nucleate minerals in vitro is known.
• Understanding intrafibrillar mineralization is key to biomimetic material design.

Purpose of the Study:

• To investigate the chemomechanical effects of mineral precipitation within collagen fibrils.
• To quantify the stress generated during intrafibrillar mineralization.
• To analyze the kinetics of mineral deposition and its impact on collagen structure.

Main Methods:

• Precipitation of strontium- and calcium-based minerals within collagen fibrils.
• In-operando synchrotron X-ray scattering to analyze mineral deposition kinetics.
• Measurement of mechanical stress generated by mineral-collagen composites.

Main Results:

• Mineral precipitation within collagen fibrils induces significant fibril contraction, generating stresses up to several megapascals.
• The magnitude of contraction stress depends on the type and quantity of mineral formed.
• Intrafibrillar mineralization, but not extrafibrillar deposition, causes fibril contraction.
• This process occurs even when collagen is fully immersed in water.

Conclusions:

• Intrafibrillar mineralization is a potent mechanism for generating mechanical stress within collagenous tissues.
• This process creates a reinforced composite material with tensile fibers, analogous to reinforced concrete.
• The findings offer insights into bone formation and the development of novel biomimetic materials.