Experimental and Modeling Study of Collagen Scaffolds with the Effects of Crosslinking and Fiber Alignment

Abstract

Collagen type I scaffolds are commonly used due to its abundance, biocompatibility, and ubiquity. Most applications require the scaffolds to operate under mechanical stresses. Therefore understanding and being able to control the structural-functional integrity of collagen scaffolds becomes crucial. Using a combined experimental and modeling approach, we studied the structure and function of Type I collagen gel with the effects of spatial fiber alignment and crosslinking. Aligned collagen scaffolds were created through the flow of magnetic particles enmeshed in collagen fibrils to mimic the anisotropy seen in native tissue. Inter- and intra- molecular crosslinking was modified chemically with Genipin to further improve the stiffness of collagen scaffolds. The anisotropic mechanical properties of collagen scaffolds were characterized using a planar biaxial tensile tester and parallel plate rheometer. The tangent stiffness from biaxial tensile test is two to three orders of magnitude higher than the storage moduli from rheological measurements. The biphasic nature of collagen gel was discussed and used to explain the mechanical behavior of collagen scaffolds under different types of mechanical tests. An anisotropic hyperelastic constitutive model was used to capture the characteristics of the stress-strain behavior exhibited by collagen scaffolds.

3D Collagen Alignment Limits Protrusions to Enhance Breast Cancer Cell Persistence

“…Our results show that collagen prealigned by strain is stiffer than a random collagen matrix of the same density and that the stiffness is greatest along the axis of alignment. Xu et al (50) previously conducted biaxial tensile testing of collagen prealigned by flow of magnetic beads and showed that after fixation, gels aligned parallel to the direction of alignment were stiffer than gels aligned orthogonally. Here, we obtained similar findings utilizing uniaxial tensile testing and a simpler, more robust approach to induce prealignment by strain rather than flow of magnetic beads embedded in the matrix.…”

An Experimental and Modeling Study of the Viscoelastic Behavior of Collagen Gel

“…During gelation, the polyethylene bars were polymerized into the collagen gel. The collagen gel was then immersed in 0.25% GP solutions for another 6 hs in the incubator for crosslinking [11]. The collagen gel was then rinsed with distilled water to remove the residual GP solutions.…”

“…[14] for more detailed explanation of the model. This constitutive model was adopted in our earlier study and was able to capture both the isotropic and anisotropic hyperelastic behaviors of collagen gel [11].…”

“…Furthermore, material parameters in the viscous model are obtained through analysis of the relaxation time spectrum. We have previously studied the effects of crosslinking on the elastic properties of collagen gel [11]. Some of the experimental approaches were adopted in the present study.…”

Rho family GTPases: Making it to the third dimension

“…Aligned collagen is likely stiffer than randomly organized matrices ((Xu et al, 2011) and unpublished data), and therefore may promote elevated Rho at cell-matrix contacts that are further restricted by the organization of the matrix. Indeed, we find in vivo that active Rho is organized within elongated protrusions by the orientation of the underlying collagen matrix (Figure 2).…”