Sterilization and preservation influence the biophysical properties of human amnion grafts

The introduction of amniotic membrane (AM) transplantation in ophthalmic surgery holds great promise and in many clinical situations it offers an alternative to existing management options. The purpose of this study was to examine the influence of established sterilization and preservation procedures on biophysical and histological properties of AM grafts. Amnion was sterilized by peracetic acid/ethanol sterilization [PES] and preserved by air-drying (sterile laminar flow) [AD] or in glycerol [GLYC]. Unsterilized AM were preserved at -80 degrees C [-80 degrees C] and served as an experimental control. Amnion allografts were characterized by the determination of their thickness, moisture vapour permeability (MVP), oxygen permeability (OPERM), tensile strength and sulphur content. Immunostaining for tissue-specific and basement membrane-related proteins was performed. Differences in biophysical parameters were found between the unsterilized allografts and the sterilized, air-dried or glycerol-preserved allografts. [PES/AD] showed the highest MVP and OPERM, the highest tensile strength and the lowest sulphur content and thickness. [PES/GLYC] exhibited the lowest OPERM and the highest thickness compared to [-80 degrees C] and [PES/AD]. Collagen types V and VII were preserved the best in the control group. Sterilization and preservation affect biophysical properties important for the use of AM as allogenic grafts. It has to be determined if any change, as noted, has a clinical impact.