Role of Storage on Changes in the Mechanical Properties of Tendon and Self-Assembled Collagen Fibers

Abstract

Fibrous collagen networks are the major elements that provide mechanical integrity to tissues; they are composed of fiber forming collagens in combination with proteoglycans (PGs). Using uniaxial tensile tests we have studied the viscoelastic mechanical properties of rat tail tendon (RTT) fibers and self-assembled collagen fibers that were stored at 22 degrees C and 1 atm of pressure. Our results indicate that storage of RTT and self-assembled type I collagen fibers results in increased elastic and viscous components of the stress-strain behavior consistent with the hypothesis that storage causes the introduction of crosslinks. Analysis of the elastic and viscous mechanical data suggests that the elastic constant of the collagen molecule in RTT is about 7.7 GPa. Measurement of the viscous component of the stress-strain curves for RTTs and self-assembled collagen fibers suggests that PGs may increase the viscous component and effectively increase the collagen fibril length.

Collagen network strengthening following cyclic tensile loading

“…For consistency, DDCS specimens were tested within 6 h after rsfs.royalsocietypublishing.org Interface Focus 6: 20150088 sterilization. Long-term storage of in vitro assembled collagen at room temperature and pressure has been shown to significantly increase the ultimate tensile strength [44]. The collagen concentration was estimated from the dimensions of the dialysis cassette and the dehydrated thickness (see method section on Transmission electron microscopy) to be 293 + 89 mg ml 21 .…”

The past, present and future in scaffold-based tendon treatments

“…This macroscopic crimp has been characterised as the shock absorber of tendons that permits non-damaging longitudinal elongation of fibrils within the tissue [261,282]. At strains beyond 2% strain, the low modulus of the toe region gives rise to the nonlinear heel region, during which reorientation and un-crimping of the collagen fibrils and stretching of the triple helix, the non-helical ends and the cross-links takes place [269,271,283]. When collagen is stretched beyond the heel region, no further extension is possible [259,270,284,285], the wavy pattern is now straightened and cross-links and fibrils start breaking [261].…”

Correlating Mechanical Properties with Aggregation Processes in Electrochemically Fabricated Collagen Membranes

“…Tendons, for example, are aligned collagen-based connective tissue whose elastic properties have been widely studied at macroscopic length scales. [1][2][3] However, mechanical property investigations at smaller length scales, relevant to the local environment experienced by a cell, require smaller probes. Force-displacement curves obtained with atomic force microscopy (AFM) cantilevers, whose tips have radii of curvature on the order of tens of nanometers, can be used in conjunction with appropriate mathematical models to describe the tipsample contact mechanics and to estimate the Young's modulus and other structural parameters in a range of materials.…”