Heparin-modified dendrimer crosslinked collagen matrices for the delivery of heparin-binding epidermal growth factor

A tissue engineered corneal equivalent (TECEs) requires host integration to achieve adequate anchorage and long-term device stability. Corneal integration through epithelialization and stromal integration can be manipulated by growth factors. We investigated the potential of heparin-binding epidermal growth factor (HB-EGF) for mediating interactions with human corneal epithelial cells (HCEC) and compared its efficacy to epidermal growth factor (EGF) in vitro. Furthermore, we utilized heparinized dendrimer crosslinked collagen gels, intended for use as TECE, for delivery of HB-EGF in a sustained manner. HCEC were exposed to HB-EGF at varying concentrations between 0.1 and 1000 ng/mL. Cell proliferation increased with growth factor concentration up to a concentration of 50 ng/mL, suggesting growth factor receptor down-regulation at higher HB-EGF concentrations. Response to HB-EGF was comparable to EGF at low concentrations of 0.1 and 1 ng/mL but at a concentration of 10 ng/mL, HB-EGF induced significantly better proliferation than EGF. Proliferation was found to be dependent on the initial seeding density. Heparinized dendrimer crosslinked collagen (CHG) gels were capable of HB-EGF uptake, which was influenced by heparin concentration within the gel, growth factor concentration and exposure time to the growth factor. HB-EGF release followed first order kinetics, with ∼90% of the growth factor released after 2 weeks. Growth factor stability was verified with in vitro HCEC culture studies. Bioavailability was maintained in the gels through heparin interaction. Overall, HB-EGF induced proliferation of HCEC in vitro and can be released from heparinized collagen gels making it potentially suitable for promoting epithelialization of TECEs.