Bio-Orthogonally Crosslinked, In Situ Forming Corneal Stromal Tissue Substitute

In this study, an in situ forming corneal stromal substitute based on collagen type I crosslinked by bio-orthogonal strain-promoted azide–alkyne cycloaddition (SPAAC) is presented. The crosslinked collagen gel has greater transparency compared to non-crosslinked collagen gels. The mechanical properties of the gels are controlled by changing functional group ratios and conjugated collagen concentrations. Higher concentrations of conjugated collagen yield enhances mechanical properties, where the storage modulus increases from 42.39 ± 8.95 to 112.03 ± 3.94 Pa after SPAAC crosslinking. Encapsulated corneal keratocytes grow within the SPAAC-crosslinked gels and corneal keratinocytes are supported on top of the gel surfaces. SPAAC-crosslinked gels support more favorable and stable keratinocyte morphology on their surface compared to non-crosslinked gels likely as a result of more optimal substrate stiffness, gel integrity, and resistance to degradation. SPAAC-crosslinked collagen gels with and without encapsulated keratocytes applied to rabbit corneas in an organ culture model after keratectomy exhibit surface epithelialization with multilayered morphology. The novel in situ forming gel is a promising candidate for lamellar and defect reconstruction of corneal stromal tissue.