Design and analysis of braid-twist collagen scaffolds

Collagen type I fiber-based scaffolds for anterior cruciate ligament (ACL) replacement were evaluated for their mechanical properties and their ability to promote cellular proliferation. Prior to scaffold formation, two crosslinking methods were investigated on individual reconstituted collagen type I fibers, ultraviolet radiation, and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). Crosslinking with EDC for 4 hr yielded mechanical properties similar to the human ACL; therefore, scaffold crosslinking was done with EDC for 4 hr. A braid-twist scaffold design was used, and scaffolds were left uncrosslinked, crosslinked after the addition of gelatin, or crosslinked without gelatin. The ultimate tensile strength, Young's modulus, and viscoelastic properties of the scaffolds were then evaluated. In order to assess cellular response on the scaffolds, primary rat ligament fibroblast cells were seeded upon the scaffolds. Cell activity was evaluated at days 7, 14, and 21 using a Cell Titer 96(®) AQueous One Solution Cell Proliferation Assay (MTS Assay). The mechanical testing results showed that among the three scaffold groups, the crosslinked scaffolds without gelatin displayed an ultimate tensile strength, Young's modulus, and viscoelastic properties that were closest to the human ACL. Improvements are still desired to enhance the mechanical compliance and ductility of these scaffolds. Cell activity was observed on all cell-seeded scaffolds by day 7, but by day 21 only the crosslinked scaffolds without gelatin displayed increased cellular activity compared with the negative controls. Although improvement is still needed, the results suggest that these scaffolds have the potential to contribute toward an ACL replacement strategy.