Effectiveness of human amnion preserved long-term in glycerol as a temporary biological dressing

Human amnion as a temporary biological wound dressing has remained a benefi cial and cost-effective means of treating burns in developing countries. Th e aim of this study was to determine whether human amnion that has undergon e long-term preservation in glycerol is an effective biological dressing co mpared to fresh amnion and glycerol-preserved human skin. Samples of human amnion and skin were preserved in sterile containers of 85 % glycerol at 4 degrees C for over a year. Dorsal full-thickness or split-t hickness skin wounds were produced in rats. The defects were divided into f our areas, each of which was covered with preserved amnion, fresh amnion, p reserved skin, or left uncovered as a control, The materials on the wounds were evaluated macroscopically and microscopically after 2, 4, 7, 10 and 14 days. The primary take or adherence of the grafts on full-thickness wounds was evaluated at 4 and 7 days, and material performance was scored based o n several macroscopic and microscopic criteria. The bacteria levels reducin g effect of the materials were examined by quantitative bacteriology in hea vily infected full-thickness scald burn wounds of rats. Qualitative cultures confirmed that the storage conditions the materials we re subjected to for over a year were aseptic and that the amnion and skin h ad maintained their characteristic properties. All materials were found eff ective on partial-thickness rat wounds as a cover under which re-epithelial ization was completed by 7 days. The preserved skin performed better than e ither preserved or fresh amnion on full-thickness wounds but the performanc e of preserved amnion was comparable to that of fresh amnion. Glycerol-pres erved amnion was found to be as effective as fresh amnion or skin in terms of decreasing bacterial levels in infected rat burn wounds. Amnion stored in glycerol is reliable and effective for a long period of ti me. Amnion banking could provide an unlimited quantity of biologic dressing for burn treatment at low cost, a factor that is particularly important in developing countries. (C) 1999 Elsevier Science Ltd and ISBI. All rights r eserved.