title: Crosslinked collagen hydrogels as corneal implants: effects of sterically bulky vs. non-bulky carbodiimides as crosslinkers.
abstract: We have previously shown that recombinant human collagen can be crosslinked with N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide (EDC) to fabricate transparent hydrogels possessing the shape and dimensions of the human cornea. These corneal implants have been tested in a Phase I human clinical study. Although these hydrogels successfully promoted corneal tissue and nerve regeneration, the gelling kinetics were difficult to control during the manufacture of the implants. An alternative carbodiimide capable of producing hydrogels of similar characteristics as EDC in terms of strength and biocompatibility, but with a longer gelation time would be a desirable alternative. Here, we compared the crosslinking kinetics and properties of hydrogels crosslinked with a sterically bulky carbodiimide, N-Cyclohexyl-N'-(2-morpholinoethyl) carbodiimide metho-p-toluenesulfonate (CMC), with that of EDC. CMC crosslinking was possible at ambient temperature whereas the EDC reaction was too rapid to control and had to be carried out at low temperatures. The highest tensile strength obtained using optimized formulations were equivalent, although CMC crosslinked hydrogels were found to be stiffer. The collagenase resistance of CMC crosslinked hydrogels was superior to that of EDC crosslinked hydrogels while biocompatibility was similar. We are also able to substitute porcine collagen with recombinant human collagen and show that the in vivo performance of both resulting hydrogels as full-thickness corneal implants is comparable in a mouse model of an orthotopic corneal graft. In conclusion, CMC is a viable alternative to EDC as a crosslinker for collagen-based biomaterials for use as corneal implants, and potentially for use in other tissue engineering applications.
authors.affiliation: Ottawa Hospital Research Institute and University of Ottawa Eye Institute, Ottawa, Ontario, Canada.
authors.forename: Jae-Il
authors.initials: JI
authors.lastname: Ahn
authors.forename: Lucia
authors.initials: L
authors.lastname: Kuffova
authors.forename: Kimberley
authors.initials: K
authors.lastname: Merrett
authors.forename: Debbie
authors.initials: D
authors.lastname: Mitra
authors.forename: John V
authors.initials: JV
authors.lastname: Forrester
authors.forename: Fengfu
authors.initials: F
authors.lastname: Li
authors.forename: May
authors.initials: M
authors.lastname: Griffith
mesh_terms: D000818:Animals; D002234:Carbodiimides / Q000737:chemistry*; D024042:Collagen Type I / Q000737:chemistry*; D003315:Cornea / Q000166:cytology / Q000601:surgery*; D016039:Corneal Transplantation / Q000295:instrumentation*; D003432:Cross-Linking Reagents / Q000737:chemistry*; D055119:Elastic Modulus; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006244:Hardness; D020100:Hydrogels / Q000737:chemistry*; D008422:Materials Testing; D051379:Mice; D008807:Mice, Inbred BALB C; D019736:Prostheses and Implants; D013552:Swine; D013718:Tensile Strength; D016896:Treatment Outcome
chemical_list: D002234:Carbodiimides; D024042:Collagen Type I; D003432:Cross-Linking Reagents; D020100:Hydrogels