Amniotic membrane as a battlefield dressing for the ocular surface

TL;DR: A systematic review of the evidence of AM treatment of acute chemical injuries was conducted, and a framework was proposed for optimising the dried tissue through thermal, moisture sorption and surface analytical techniques.

Abstract: The use of amniotic membrane (AM) as a dressing for ocular surface injuries has attracted the interest of the military ophthalmological community. First applied in the 1930s, the tissue is widely used today, although clinical indications for treatment are incompletely defined. While AM is most commonly stored frozen and thawed before use, dried AM is preferred for logistical reasons. Optimal preservation of the tissue is necessary to preserve its quality. The effect of drying on the physical and biological properties of the tissue are unknown. A systematic review of the evidence of AM treatment of acute chemical injuries was conducted. A framework was proposed for optimising the dried tissue through thermal, moisture sorption and surface analytical techniques. The physical properties of AM preparations were compared by mechanical testing and mathematical modelling, and an attempt was made to cross-link the AM collagen. Inflammatory aspects of the tissue were assessed by immunological techniques, zymography and macrophage assays. There is a lack of high quality evidence to support the clinical application of AM for acute burns. Complex interactions were demonstrated between the dried tissue, its excipients and moisture, suggesting novel ways of optimising the product. The mechanical properties of the dried membrane indicated that the process adversely affected the tissue, and artificial cross-linking could not be achieved. While the presence of antimicrobial peptides was not clearly established, the elution of collagenolytic enzymes was shown in therapeutic preparations of AM. The production of tumour necrosis factor by macrophages, which adhere to the spongy layer of AM, was suppressed. This project makes original contributions relevant to the use of dried AM as a biomaterial in ophthalmic surgery. Further refinements of this work, animal model experimentation and clinical trials may support its future acceptance as a clinical application.