TABLE 1.

Bending and shear moduli of collagen type I fibrils obtained from scanning bending measurements

Collagen type I fibril	Conditions	Number of samples	Range of diameters‡ (nm)	Bending moduli¶ (GPa)	Shear modulus§ (MPa)
Native	Dry	18	187–305	3.9–1.0	33 ± 2
Cross-linked*	Dry	11	205–303	3.1–1.7	74 ± 7
Native	PBS buffer†	12	280–426	0.17–0.07	2.9 ± 0.3
Cross-linked*	PBS buffer†	13	287–424	0.14–0.06	3.4 ± 0.2

^*Cross-linking was performed with EDC and NHS in MES buffer.

^†PBS: phosphate-buffered saline, pH = 7.4.

^‡Ranges of diameters of different fibrils used in the mechanical tests. The error in the diameter of individual fibrils is ∼3% (SE) calculated from multiple measurements on the same fibril.

^¶Ranges of bending moduli determined from fibrils with different diameters. A 23% relative error is estimated for the value of the bending modulus determined for individual fibrils.

^§The error in the shear modulus is the standard error of the weighted least-squares fit parameter.