Micromechanical bending of single collagen fibrils using atomic force microscopy

Area of Science:

• Biomaterials Science
• Mechanical Engineering
• Biophysics

Background:

• Collagen fibrils are fundamental structural components of connective tissues.
• Understanding their mechanical properties is crucial for tissue engineering and understanding disease.
• Existing methods often lack the precision to analyze individual fibrils.

Purpose of the Study:

• To develop and validate a novel micromechanical technique for assessing single collagen fibril mechanical properties.
• To determine the Young's modulus of native and cross-linked collagen fibrils.
• To investigate the impact of glutaraldehyde cross-linking on fibril stiffness.

Main Methods:

• Isolation of single collagen fibrils from various collagenous materials.
• Utilized atomic force microscopy (AFM) with a tip-less cantilever for force-indentation measurements.
• Employed bending tests on fibrils suspended across micro-channels on a poly(dimethyl siloxane) (PDMS) substrate.
• Applied linear elastic theory for isotropic materials to calculate Young's modulus.

Main Results:

• Determined Young's modulus for native collagen fibrils to be 5.4 ± 1.2 GPa (freely supported) or 1.4 ± 0.3 GPa (fixed ends).
• Glutaraldehyde cross-linking significantly increased the Young's modulus to 14.7 ± 2.7 GPa (freely supported) or 3.8 ± 0.8 GPa (fixed ends).
• Established the range of Young's moduli for native and cross-linked fibrils.

Conclusions:

• The developed AFM-based micromechanical technique provides a precise method for evaluating single collagen fibril mechanics.
• Glutaraldehyde cross-linking substantially enhances the stiffness of individual collagen fibrils.
• These findings offer valuable insights into collagenous material biomechanics and potential applications in biomaterial design.