Active wound coverings

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  1. 1. P R E S E N T E D B Y : D R . S AR AN G G O T E C H A Active Wound Coverings: Bioengineered Skin and Dermal Substitutes. 1
  2. 2. OVERVIEW OF STRUCTURE OF SKIN 2
  3. 3. EPIDERMIS EPIDERMAL CELLS Keratinocytes Melanocytes . Langerhans cells Merkel cells 3
  4. 4. Dermis Consists of connective tissue, amorphous ground substance composed of proteoglycans, blood vessels, nerves, lymphatics and muscles. Dermis can be divided into Superficial papillary dermis superficial vascular plexus Reticular dermis. Collagen Elastin Extracellular matrix 4
  5. 5. EXTRACELLULAR MATRIX Extracellular matrix proteoglycans glycosaminoglycans + core proteins Hyaluronic dermatan keratan chondroitan heparan Acid sulphate sulphate sulphate sulphate 5
  6. 6. INTRODUCTION In the last few decades, there has been a tremendous increase in the development of new active wound coverings and bioengineered skin substitutes. Increased understanding of wound healing and the complex interactions of cells, extracellular matrix molecules, growth factors, and various signaling molecules brought new materials that optimized wound healing and minimized scarring. These developments overcame the biochemical difficulties of chronic wounds and the challenges of extensive wounding found with large body surface area burns. 6
  7. 7. INTRODUCTION Research has shown that moist wound healing creates a more optimal healing environment and this knowledge led to the development of various occlusive synthetic dressings that improved the outcome and addressed the various issues of acute and chronic wound environments. These new synthetic polymer dressings have improved the outcome in many situations and and slowly replaced the centuries old standard of gauze-type dressings. 7
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  9. 9. INTRODUCTION They can maintain an ideal moist environment, help autolytic debridement, prevent infection, and speed up granulation and epithelialization. However they are not always able to correct the challenges of complex chronic wounds or extensive wounding of the skin with large body surface area epidermal loss. 9
  10. 10. INTRODUCTION In recent years, a wide array of biologically active materials and skin substitutes has been developed. Although an ideal skin substitute is not yet available these products address the various challenges of wound healing. 10
  11. 11. Properties of an ideal skin substitute Increase healing Decrease pain Are safe Are cost effective Are nonallergenic/- antigenic/-toxic Are easy to apply and remove Provide an infection barrier Are durable/resist shearing Recreate epidermis and dermis Provide long term/permanent wound cover Are easy to manufacture and store Are easy to obtain/easily available Have a long shelf life 11
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  14. 14. EXTRACELLULAR MATRIX MATERIALS(ECM) Help change environment of the wound and essentially can be considered active within the wound. Maintain ideal moist wound healing environment by absorbing excessive fluid or donating moisture. Help dermal regeneration, absorb bacterial chemical byproducts and destruct wound enzymes (matrix metalloproteinases [MMPs]). 14
  15. 15. ECM (contd) chemically binds the various metalloproteinases and inactivates them. Protect local growth factors from degradation by MMPs and therefore growth factors can remain biologically active in the wound environment. Dressings specifically designed for helping reduce the high levels of MMPs composed of a mixture of collagen and oxidised regenerated cellulose or alginate fibres 15
  16. 16. ECM (contd) Examples of such wound dressings are Promogram Wound Matrix Prisma Fibracol plus collagen(Johnson and Johnson) 16
  17. 17. ECM (contd) To aid dermal regeneration, other materials composed of collagen or hyaluronic acid from various animal sources are used in the wound This exogenous collagen chemotactic for fibroblasts and macrophages and also provides temporary 3 dimensional scaffold to help with ingrowth of tissue 17
  18. 18. ECM (contd) PERMACOL MEDIFILL SK IN TEMP MATRIDERM 18
  19. 19. MATRIDERM Dermal implant made of native bovine collagen coated with elastin This matrix results in a better reconstruction of the dermis than pure collagen matrices. Allows the ingrowth of host fibroblasts and other cells to regenerate a dermis with properties closer to normal uninjured skin. 19
  20. 20. Matriderm combined with autologous grafting gave better results in terms of elasticity and vascularity than skin grafting alone. Ryssel H, Gazyakan E, Germann G, et al. The use of matriderm in early excision and autologous skin grafting in burns- a pilot study. Burns 2008; 34: 93-7. Fibronectin formation of the dermis reconstructed with MatriDerm was comparable to normal uninjured skin. Van Zuijlen PP, Lamme EN, van Galen MJ, et al. Long term results of a clinical trial on dermal substitution. A light microscopy and Fourier analysis based evaluation. Burns 2002;28:151-160. MATRIDERM 20
  21. 21. Matriderm also allows the clinician to simultaneously place an autologous split thickness skin graft with the same procedure, which helps minimise the need for a second operation in burn surgery. Van Zuijlen PP, Van Trier AJ, Vloemans JF et al. Graft survival and effectiveness of dermal subsitiution in burns and reconstrive surgery in a one stage grafting model. Plast Reconstr Surg 2000; 106: 615- 23. MATRIDERM 21
  22. 22. OASIS WOUND MATRIX Derived from porcine intestinal submucosa. Indicated for various types of partial and full thickness wounds, such as burns as well as traumatic and various chronic ulcers. This natural scaffold, which contains native ECM, and various growth factors is incorporated and absorbed into the wound base. 22
  23. 23. OASIS WOUND MATRIX In vivo studies have shown angiogenesis into the matrix. Hodde JP, Ernst DM, Hiles MC. An investigation of the long term bioactivity of endogenous growth factor in OASIS Wound Matrix. J Wound Care 2005; 14: 23-5 Oasis wound matrix has been evaluated in a randomised controlled clinical trial in the treatment of venous leg ulcers, and after 12 weeks, 55% of patients were healed in the Oasis group and only 34% in the control group. Oasis Wound Matrix Web site 2010. Available at : http://www.oasiswoundmatrix.com. Accessed May 23,2010. 23
  24. 24. ACELLULAR SKIN REPLACEMENTS SYNTHETIC BILAYER SUBSTITUTES ALLOGENIC ACELLULAR SUBSTITUTES 24
  25. 25. SYNTHETIC BILAYER SUBSTITUTES Materials that consist of a porous matrix, which contains collagen, hyaluronic acid, fibronectin, or other acellular matrix proteins, and a thin layer of silicone. Helps protect the wound from moisture loss and infection. Examples 25
  26. 26. BIOBRANE Biosynthetic skin substitute Bilaminate membrane consisting of nylon mesh with covalently bound porcine type I collagen peptide and a thin layer of silicone. When applied to a partial thickness or freshly excised full thickness wound, it adheres and provides a temporary skin barrier. 26
  27. 27. BIOBRANE As the wound heals, fibroblasts and capillaries grow under the bilayer skin substitute and regenerate tissue in the dermis. The silicone layer functions as the epidermis, and pores in the silicone material allow some fluid to escape. In fairly superficial wounds membrane binds to the wound and is gradually replaced by host epithelium from adnexae and wound edges. 27
  28. 28. BIOBRANE In full thickness wounds material stimulates granulation tissue and prepares the bed for autologous grafting, although the silicone membrane and the nylon mesh need to be removed before the procedure. 28
  29. 29. AWBAT Composed of a very thin, porous silicone membrane bound to a loosely knit nylon fabric, which is coated with a mixture of porcine collagen peptides. Not covalently bound interact more quickly with fibrin in the wound and allows better acute adherence during the initial phase of wound closure. More uniform distribution of pores in the silicone layer allows better fluid and moisture permeability and decreases the development of seromas at the wound site. 29
  30. 30. INTEGRA DERMAL REGENERATION TEMPLATE Bilayer matrix that provides a scaffold for dermal regeneration and temporary wound coverage. Dermal replacement layer consists of a porous matrix of fibres of cross linked bovine collagen and chondroitin-6-sulfate manufactured with a controlled porosity and defined degradation rate. 30
  31. 31. Epidermal substitute layer is made of synthetic polysiloxane polymer and functions to control moisture loss from the wound and provide protection from infection. The collagen dermal replacement layer serves as a scaffold for the infiltration of fibroblasts and various other cells during the healing process Over time,dermal layer of integra is degraded,replaced by host tissue,and neodermis is regenerated from template INTEGRA DERMAL REGENERATION TEMPLATE 31
  32. 32. FUTURE DEVELOPMENTS AND MODIFICATIONS OF ECM MATERIALS Delivery of antimicrobial agents, growth factors, and DNA to further enhance wound healing. Colonisation of wound with bacteria occurs quickly formation of a bacterial biofilm chronic infections. Incorporation of sliver, cadexomer iodine, and other antimicrobials in the ECM materials delay wound colonisation and biofilm formation. 32
  33. 33. ALLOGENIC ACELLULAR SUBSTITUTES Human cadaver allograft GOLD STANDARD for temporary coverage after burn wound excision. Dermal allografts human cadaveric skin that is cryopreseved, lyophilized,and glycerolized to remove donor cellular ,infectious and antigenic materials. Remaining structures serves as a scaffolding or template for the ingrowth of host fibroblasts and vascular tissue and helps regenerate dermal t