Photoactivated growth factor release from bio-orthogonally crosslinkedhydrogels for the regeneration of corneal defects

In situ-forming hydrogels are an attractive option for corneal regeneration, and the delivery of growth factorsfrom such constructs have the potential to improve re-epithelialization and stromal remodeling. However,challenges persist in controlling the release of therapeutic molecules from hydrogels. Here, an in situ-forming bioorthogonallycrosslinked hydrogel containing growth factors tethered via photocleavable linkages (PC-HAColhydrogel) was developed to accelerate corneal regeneration. Epidermal growth factor (EGF) was conjugated tothe hydrogel backbone through photo-cleavable (PC) spacer arms and was released when exposed to mild intensityultraviolet (UV) light (2–5 mW/cm2, 365 nm). The PC-HACol hydrogel rapidly gelled within a few minuteswhen applied to corneal defects, with excellent transparency and biocompatibility. After subsequentexposure to UV irradiation, the hydrogel promoted the proliferation and migration of corneal epithelial cells invitro. The rate of re-epithelialization was positively correlated to the frequency of irradiation, verified through exvivo rabbit cornea organ culture studies. In an in vivo rat corneal wound healing study, the PC-HACol hydrogelexposed to UV light significantly promoted re-epithelialization, the remodeling of stromal layers, and exhibitedsignificant anti-scarring effects, with minimal α-SMA and robust ALDH3A1 expression. Normal differentiation ofthe regenerated epithelia after healing was evaluated by expression of the corneal epithelial biomarker, CK12.The remodeled cornea exhibited full recovery of corneal thickness and layer number without hyperplasia of theepithelium.