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Maria Borrelli, Stephan Reichl, Yaqing Feng, Marc Schargus, Thomas Klink, Johana E. Sold, Rainer Guthoff, Gerd Geerling; Keratin Films in Ocular Surface Reconstruction: Biomechanical Properties and Surgical Feasibility. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5159.
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© ARVO (1962-2015); The Authors (2016-present)
Cornea and amniotic membrane (AM) transplantation are used to reconstruct the ocular surface. Lack of standardization, limited transparency and reduced biomechanical resistance are some disadvantages of these graft materials. Keratin has been proposed as a transparent carrier, suitable for corneal epithelial cell expansion and ocular surface reconstruction. We studied the biomechanical properties of keratin films, before and after sterilization, and their surgical feasibility for ocular surface reconstruction.
Keratin films, prepared mixing aqueous keratin dialysate and alkaline keratin dialysate (at ratios of 100/0, 90/10, 80/20, 70/30), cured at temperatures between 70° and 110°, were studied in vitro for tensile strength (Fmax) and ex vivo for surgical feasibility. 100 and 90/10 films cut in 12 mm disc were clamped in a Zwicki-LineZ0.5 material testing machine after a 10.0 Ethilon suture was passed through its geometrical centre. Surgical feasibility was assessed by 7 anterior segment surgeons who sutured 7 films each into a 7.5mm round keratectomy of porcine eyes. AM were sutured as control in the same manner. The percentage of tight sutures and breaks was counted. A subgroup of 3 surgeons repeated the experiment with sterilized films (plasma, autoclave and ethanol) to evaluate the impact of sterilization on the biomechanical properties.
The Fmax was for amniotic membrane 0.26N, for 100/0 keratin between 0.02N (at 70°) and 0.33N (at 110°), and for 90/10 keratin between 0.02N (at 70°) and 0.1N (at 110°). The Fmax was significantly reduced in 100/0 films by plasma sterilization (p=0.01). The surgical ex vivo assessment showed that tight sutures and breaks in the material were achieved in AM in 100% and 0% respectively and in 90/10 films in 58%±28 and 65%±29 respectively. These features were not modified by any sterilization methods.
With the appropriate choice of sterilization method and some material modification, films from human keratin may represent an alternative for ocular surface reconstruction.
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