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Andres De la Hoz, Irene E Kochevar, Fiorenzo Omenetto, Susana Marcos; Photobonded silk-fibroin films for corneal dressing. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3218.
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Amnionic membrane has been used as a dressing for corneal wounds, and shown to successfully bond, suturelessly, to the cornea by a light-initiated technique. In the quest for biocompatible, transparent, accessible, nonallogeneic tissues for corneal dressing application, we evaluated silk fibroin films (SFF) and their ability to photo-chemically bond to the cornea.
SFFs were developed by mixing a solution of lyophilized bombyx mori silk fibroin, glycerol and water, drying, then hydrating the films to remove the glycerol. Photo-induced bonding of SFFs to corneal tissue and mechanical strength were assessed on porcine corneas (n=90). For bonding strength testing, 5x20mm SFF strips (50 μm thick) were used. Corneas (n=72) were de-epithelialized and cut into strips (width: 5mm). SFF strips were soaked in 0.01% Rose Bengal (RB) solution and placed on top of the corneal strips. A solid-state green light source (543 nm) was used to irradiate the strips at 0.175 W/cm2 for varying exposure times (5,10,15 min). Unstained silk strips and non-irradiated RB-silk strips were used as controls. Silk-cornea strips were mounted on a uniaxial stretcher for extensiometry tests. Maximum bond breaking force was recorded. For inflation testing, 10-mm diameter SFF disks were used. De-epithelialized porcine eyes were pierced to make a 2-mm port in the central corneal surface. A syringe needle was interested through the optic nerve. Viscoelastic solution was injected into the anterior chamber to block leakage through the port. The surface was dried, then silk discs were placed on the cornea and irradiated (0.175 W/cm2, 10 min). The eye was inflated by pumping saline solution into it through the syringe. The volume of liquid was recorded until leakage/breakage of the bond.
The bond breaking force for irradiated RB-stained silk-cornea strips was 4.3-5.8 times higher than for irradiated non-stained films. The force required to break the bond increased as the irradiation time increased for RB-stained films, from 64 to 383 mN (1.95 mN per J/cm2), but remained constant for the unstained control films. In inflation tests, the force required to break the bonding is greater when the SFF dressing had been previously stained in RB and irradiated, compared to an irradiated unstained SFF.
These results indicate that a rapid, light-activated technique produces strong, immediate bonding between SFFs and cornea ex vivo and merits further evaluation.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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