Collagen gels crosslinked by photoactivation of riboflavin for corneal defect repair

Abstract

Purpose : Corneal disease and injuries resulting in stromal defects put the cornea at risk of perforation and/or permanent scarring leading to blindness. A biomaterial that not only occupies a defect but also supports epithelialization may improve clinical outcomes and has the potential to reduce the need for further surgical intervention and the cadaveric donor corneal tissue it typically requires. Light activation of riboflavin is being used to crosslink and strengthen stromal collagen in cases of corneal ectasia. Here, we evaluate the use of this modality to also crosslink exogenously supplied collagen in situ at corneal wound sites.

Methods : Riboflavin was mixed with native, unconjugated collagen type I of varying concentrations and exposed to blue and UV light at increasing time intervals. Mechanical properties of the resulting collagen gels, including both storage and loss moduli as a function of exposure time, were studied using a rheometer. Collagen gels photoactivated with riboflavin were then evaluated in an in vivo deep keratectomy model in rabbits, where a 3.5 mm diameter and ~50% depth stromal defect was filled with the gel which was light-cured in situ. The treated eyes were clinically examined and excised after 1 week for immunohistochemical evaluation.

Results : Rheological experiments demonstrated successful gelation of collagen with increasing stiffness as a function of light exposure time using both blue light and UV light. The gels formed in situ by photoactivation of riboflavin were clinically well-tolerated and supported corneal epithelialization after 1 week in vivo. Immunohistochemical analysis exhibited expression of 4-hydroxynonenal (4-HNE) within the epithelium and alpha-smooth muscle actin within the surrounding stroma.

Conclusions : Our study suggests that riboflavin-mediated crosslinked of exogenous collagen type I has the potential to fill and stabilize corneal defects with a matrix that can support epithelialization. Further work to characterize the biological response of the cornea to this modality is merited.

This is a 2021 ARVO Annual Meeting abstract.