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R. Janjua, S. Steidl; A First Look at Biopolymer Hydrogels as Adhesive Materials in the Retina . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2980.
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Purpose: Natural polymers are advocated as biomaterials in several areas of medicine, as they are non-toxic and biocompatible with low immunogenicity. A potential area of use may be in the management of retinal holes or tears, selected retinal detachments, as well as in the placement of retinal prosthetic devices. As a preliminary study for use in the retina, two protein-polysaccharide combination gels were evaluated utilizing bovine aorta. More specifically, two enzymes, tyrosinase and transglutaminase, were used to catalyze the formation of gelatin/chitosan hydrogels. Methods: One two-inch segment of bovine aorta was overlapped to another similar segment with tyrosinase-catalyzed hydrogel, transglutaminase-catalyzed hydrogel, and transglutaminase-catalyzed hydrogel + 10% gelatin. A commercially available cyanoacrylate, known to grossly adhere to bovine aorta, was also tested for comparison. The specimens were submerged under water for approximately two hours. Mechanical testing was performed on a computer controlled uniaxial test system: the BIMaTs (Biological Materials Testing System). This allowed for evaluation of the strength of the adhesive by application of a tangential load on the aorta-adhesive-aorta composite. Stress-strain curves were generated for each biopolymer hydrogel, as well as for the cyanoacrylate. Results: All enzyme-generated hydrogels showed potential adhesive properties. Considerable stress was applied to each before fracture of the aorta-adhesive-aorta composite. Of the biopolymer hydrogels, the transglutaminase-catalyzed hydrogel was able to withhold the most amount of stress. The addition of 10% gelatin to the composite conferred an increase in tensile or stretch properties, as the strain was greater given an equal amount of applied stress (load). Conclusions: The tyrosinase and transglutaminase generated hydrogels show promise in adhering to the bovine aorta. The various formulations of these hydrogels determine their different adhesive properties. At the present time, an equivalent BiMaTs system needs to be constructed that is adequate for measurement of the strength of these adhesives on a retina-adhesive-retina composite. This will allow further assessment of the potential use of biopolymer hydrogels as adhesive materials in the retina.
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