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      Cross-Linking of Human Amniotic Membrane by Glutaraldehyde


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          Purpose: The transplantation of cryopreserved human amniotic membrane has been introduced recently for the reconstruction of the ocular surface. However, in some diseases the transplant usually dissolves rather quickly and early detachment may occur. Therefore, we tried to stabilize the amniotic transplant by applying glutaraldehyde for collagen cross-linking of the membrane. Methods: 18 human amnions were prepared. 4 × 4 cm pieces of amnion were treated with 0.1% glutaraldehyde solution for 30 min. Biomechanical force-elongation measurements were performed and resistance to enzymatic digestion by 0.1% collagenase solution was tested and compared to cryopreserved and untreated fresh amnion. 8 patients with various ocular surface defects were treated with cross-linked amnion and compared to 5 patients with cryopreserved amnion. Results: The force of the amnion cross-linked with glutaraldehyde at 2.5 mm elongation was increased statistically significant by 175% versus fresh amnion and 76.8% versus the cryopreserved amnion. Glutaraldehyde-treated membranes were virtually completely resistant to enzymatic digestion, while fresh and cryopreserved amnions were dissolved completely by day 7. In patients, the cross-linked membrane was preserved for up to 90 days without any signs of dissolution of the membrane and good transparency. Conclusions: Collagen cross-linking using glutaraldehyde leads to a significant increase in the biomechanical strength and enzymatic resistance of amnion, better transparency and less wrinkling. The cross-linked membrane does not dissolve for months and is well suited for the surface reconstruction of the cornea.

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          Most cited references6

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          Influence of different crosslinking treatments on the physical properties of collagen membranes.

          The physical properties of collagen-based biomaterials are profoundly influenced by the method and extent of crosslinking. In this study, the influence of various crosslinking treatments on the physical properties of reconstituted collagen membranes was assessed. Five crosslinking agents viz., GTA, DMS, DTBP, a combination of DMS and GTA and acyl azide method were used to stabilize collagen matrices. Crosslinking density, swelling ratio, thermo-mechanical properties, stress-strain characteristics and resistance to collagenase digestion were determined to evaluate the physical properties of crosslinked matrices. GTA treatment induced the maximum number of crosslinks (13) while DMS treatment induced the minimum (7). Of the two diimidoesters (DMS and DTBP), DTBP was a more effective crosslinking agent due to the presence of disulphide bonds in the DTBP crosslinks. T(s) for DTBP and DMS crosslinked collagen were 80 degrees C and 70 degrees C, and their HIT values were 5.4 and 2.85MN/m(2), respectively. Low concentration of GTA (0.01%) increased the crosslinking density of an already crosslinked matrix (DMS treated matrix) from 7 to 12. Lowest fracture energy was observed for the acyl azide treated matrix (0.61MJ/m(3)) while the highest was observed for the GTA treated matrix (1.97MJ/m(3)). The tensile strength of GTA treated matrix was maximum (12.4MPa) and that of acyl azide treated matrix was minimum (7.2MPa). GTA, DTBP and acyl azide treated matrices were equally resistant to collagenase degradation with approximately 6% solubilization after 5h while the DMS treated was least stable with 52.4% solubilization after the same time period. The spatial orientation of amino acid side chain residues on collagen plays an important role in determining the crosslinking density and consequent physical properties of the collagen matrix.
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            Effect of physical crosslinking methods on collagen-fiber durability in proteolytic solutions.

            We previously demonstrated that ultraviolet (UV) or dehydrothermal (DHT) crosslinking partially denatured fibers extruded from an insoluble type I collagen dispersion. In this study denaturation effects were evaluated by measuring collagen-fiber sensitivity to trypsin. Shrinkage-temperature measurements and sensitivity to collagenase served as indices of crosslinking. UV or DHT crosslinking increased the collagen-fiber shrinkage temperature, resistance to degradation in collagenase, and durability under load in collagenase. However, in trypsin solutions, solubility was significantly increased for UV (approximately 11%) or DHT (approximately 15%) crosslinked fibers compared with uncrosslinked fibers (approximately 4%). Size-exclusion chromatography indicated that no intact collagen alpha-chains were present in the soluble fraction of fibers exposed to trypsin (MW < 1 kD). Interestingly, UV-crosslinked collagen fibers remained intact an order of magnitude longer (4840 +/- 739 min) than DHT-crosslinked (473 +/- 39 min) or uncrosslinked (108 +/- 53 min) fibers when placed under load in trypsin solutions. These data indicate that mechanical loading during incubation in a trypsin solution measures denaturation effects not detected by the trypsin-solubility assay. Our results suggest that DHT-crosslinked collagen fibers should not be used as load-bearing implants. UV-crosslinked fibers may retain more native structure and should exhibit greater resistance to nonspecific proteases in vivo.
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              Surgical management of corneal ulceration and perforation


                Author and article information

                Ophthalmic Res
                Ophthalmic Research
                S. Karger AG
                April 2004
                17 March 2004
                : 36
                : 2
                : 71-77
                Departments of aOphthalmology and bAnatomy, Universitätsklinikum CGC, Dresden, Germany
                76884 Ophthalmic Res 2004;36:71–77
                © 2004 S. Karger AG, Basel

                Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                : 10 June 2003
                : 30 October 2003
                Page count
                Figures: 4, Tables: 1, References: 20, Pages: 7
                Original Paper

                Vision sciences,Ophthalmology & Optometry,Pathology


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