Abstract
Purpose :
Collagen type I is the major extracellular matrix protein of the corneal stroma. Hyaluronic acid is a ubiquitous glycosaminoglycan known to promote wound healing in the cornea. Both are promising biomaterial building blocks for engineered corneal tissue. This study optimizes and characterizes a novel, in situ-forming, simultaneous interpenetrating polymer network (IPN) hydrogel that can potentially serve as a stroma tissue substitute to fill deep corneal defects and promote epithelialization.
Methods :
The IPN was formed by mixing azide- and alkyne-conjugated collagen type I that react via strain-promoted azide-alkyne cycloaddition (SPAAC) with both methacrylated and thiolated hyaluronic acid (HA-MA, HA-SH) that react via thiol-ene reaction. The components were mixed at a 1:1 ratio and pH was increased to mildly alkaline conditions. Mechanical properties were measured by the storage modulus of the material to determine the stiffness of the gels. Light transmittance of the material after gelation was used to measure transparency. Cytocompatibility was assessed by live/dead assay and cell morphology to determine the ability of corneal epithelial cells to adhere and grow on the IPN.
Results :
Increasing the pH to mild alkaline conditions (pH 8.0) and concentration of HA-MA and HA-SH decreased gelation time in the absence of light, heat, or other molecules. The mild alkalinity of the gel resulted in no visible damage to the cornea in ex vivo and in vivo rabbit eyes. The IPN displayed a higher storage modulus than non-crosslinked collagen and the SPAAC gel. Transparency of the gel reached over 95% within the spectrum of 380nm to 700nm, compared to the previously studied gel which exhibited 85% transparency. Corneal epithelial cells plated on top of the IPN gel exhibited improved morphology compared to the HA-only gels, which can be attributed to the addition of cell adhesion-promoting ligands inherent to the collagen in the IPN matrix.
Conclusions :
The in situ-forming collagen/HA IPN hydrogel was optimized for faster gelation time while maintaining mechanical properties and increasing transparency. The IPN remains able to support epithelial cell growth while not damaging the corneal surface. These results support the potential use of the material as a scaffold for the reconstruction and regeneration of deep corneal defects.
This is a 2020 ARVO Annual Meeting abstract.