Functional evaluation of collagen fiber scaffolds for ACL reconstruction: cyclic loading in proteolytic enzyme solutions.
The mechanical properties of anterior cruciate ligament (ACL) reconstruction scaffolds were evaluated after exposure to functional challenges in vitro: cyclic loading combined with various proteolytic enzymes. Scaffolds were prepared from collagen fibers that were uncrosslinked (UNXL), crosslinked with ultraviolet irradiation (UV), or 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC; 10 or 25 mM). Structural properties of scaffolds were determined following 1-h exposure to saline, trypsin, or bacterial collagenase, with and without simultaneous cyclic tensile loading (0 to 50 g; 0.5 Hz) in vitro. The breaking load and stiffness of UNXL and UV crosslinked scaffolds were significantly reduced by exposure to either trypsin or collagenase. Cyclic loads interacted synergistically with enzymes, rendering UNXL scaffolds untestable and further decreasing the breaking load of UV crosslinked scaffolds by approximately 35%. In contrast, the breaking load and stiffness of EDC crosslinked scaffolds, which were greater than those of UNXL or UV crosslinked scaffolds, were virtually unaffected by the same load and enzyme treatments. These results suggest that EDC is more effective than UV for crosslinking and stabilizing load-bearing collagen fiber ACL reconstruction scaffolds. Application of cyclic loads and enzymes may lead to development of physiologically relevant in vitro test methods for load-bearing scaffolds.
Caruso
Andrea B
AB
Orthopaedic Research Laboratories, Department of Orthopaedic Surgery, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, MEB 424 P.O. Box 19, New Brunswick, New Jersey 08903, USA.
Dunn
Michael G
MG
D000818:Animals; D016118:Anterior Cruciate Ligament; D001672:Biocompatible Materials; D001705:Bioprosthesis; D002417:Cattle; D003094:Collagen / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000737:chemistry; D007720:Knee Prosthesis; D003012:Microbial Collagenase / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D014357:Trypsin / Q000737:chemistry*
D001672:Biocompatible Materials; D003432:Cross-Linking Reagents; D012996:Solutions; D003094:Collagen; D014357:Trypsin; D003012:Microbial Collagenase