WOUND DRESSINGS SPRING 2012 MASE542 Çağla Koşak

Outline Polymers for dermal use Commercial wound dressings Hypertropic and kelloid scars: burn injuries Skin substitutes Advances of silicone sheeting Examples from literature

Polymers for dermal use The use of polymers for skin preparations is manifold! emulsions and creams gels transdermal patches wound dressings: to prevent bulk loss of tissue in non-healing wounds such as burns, trauma, diabetic, decubitus and venous stasis ulcers a) sponge, b) hydrogel, and c) scar treatment systems penetration enhancers Schematic representation of sponge system wound dressing Valenta C. Eur. J. Pharm. Biopharm. 2004;58:279-289

Commercial wound dressings SILICONES ACRYLATES HYDROCOLLOIDS Klode J, Schöttler L. JEADV 2011, 25, 933–939

Degrees of burn injuries: first degree (the loss of the epidermal layer), second degree (the loss of the epidermal layer and a portion of the dermis), third degree (the loss of tissue through the dermis, including the hair follicles and sweat glands, and extending into the hypodermis) Ratner BD. Biomaterials Science. San Diego: Elsevier; 2004

Degrees of burn injuries: first degree (the loss of the epidermal layer), second degree (the loss of the epidermal layer and a portion of the dermis), third degree (the loss of tissue through the dermis, including the hair follicles and sweat glands, and extending into the hypodermis) Ratner BD. Biomaterials Science. San Diego: Elsevier; 2004

Degrees of burn injuries: first degree (the loss of the epidermal layer), second degree (the loss of the epidermal layer and a portion of the dermis), third degree (the loss of tissue through the dermis, including the hair follicles and sweat glands, and extending into the hypodermis) Ratner BD. Biomaterials Science. San Diego: Elsevier; 2004

Skin substitutes Best coverage for the wound is natural skin taken from the individual himself! (AUTOGRAFT) electric dermatome skin meshing device However, as long as wounds are carefully monitored for infection and kept clean and moist, most medications and membranes will perform well. Skin substitutes are classified as: Temporary, and Permanent. Ratner BD. Biomaterials Science. San Diego: Elsevier; 2004

Temporary skin substitutes Allografts from cadavers Allografts of cultured cells and collagen -treatment of diabetic foot ulcers and venous leg ulcers Xenografts (Mediskin I , Brennan Medical, Inc; EZ Derm) Synthetic membranes (Biobrane Mylan Laboratories, Inc) Hydrocolloid dressings Cells Combined with Synthetic Membranes (TransCyte, Smith & Nephew) Varios wound covers Ratner BD. Biomaterials Science. San Diego: Elsevier; 2004

Temporary skin substitutes cultured fibroblasts+ bovine collagen type I gel is seeded with epidermal keratinocytes epidermal keratinocytes stratify air Allografts from caveders Allografts of cultured cells and collagen -treatment of diabetic foot ulcers and venous leg ulcers Ratner BD. Biomaterials Science. San Diego: Elsevier; 2004

Temporary skin substitutes grafts with epidermal + dermal layer grafts are sterilized and frozen Epidermis is removed and porcine dermis is subjected to aldehyde crosslinking or Allografts from caveders Allografts of cultured cells and collagen -treatment of diabetic foot ulcers and venous leg ulcers Xenografts (Mediskin I , Brennan Medical, Inc; EZ Derm) Mediskin I, Brennan Medical EZ Derm Ratner BD. Biomaterials Science. San Diego: Elsevier; 2004

Temporary skin substitutes The wound bed comes into contact with this complex three-dimensional fabric, which helps promote clotting in the nylon matrix and adherence of the membrane to the wound bed. Allografts from caveders Allografts of cultured cells and collagen -treatment of diabetic foot ulcers and venous leg ulcers Xenografts (Mediskin I , Brennan Medical, Inc; EZ Derm) Synthetic membranes (Biobrane Mylan Laboratories, Inc) Hydrocolloid dressings Ratner BD. Biomaterials Science. San Diego: Elsevier; 2004

Temporary skin substitutes Nylon mesh, coated with porcine dermal collagen, is bonded to a thin silicon membrane. the nylon matrix is seeded with allogeneic fibroblasts. the cells deposit additional collagen, extracellular matrix proteins, and growth factors the product is kept frozen bioreactor Allografts from caveders Allografts of cultured cells and collagen -treatment of diabetic foot ulcers and venous leg ulcers Xenografts (Mediskin I , Brennan Medical, Inc; EZ Derm) Synthetic membranes (Biobrane Mylan Laboratories, Inc) Hydrocolloid dressings Cells Combined with Synthetic Membranes (TransCyte, Smith & Nephew) The silicon layer and nylon matrix are translucent, making it possible to visually monitor the wound bed. Ratner BD. Biomaterials Science. San Diego: Elsevier; 2004 http://www.burnsurgery.org/Modules/BurnWound%201/sect_VIII.htm

Permanent skin substitutes Autografts of Sheets of Cultured Keratinocytes (Epicel, Genzyme BioSurgery, Inc.) Cultured epidermal sheets have been used widely for the treatment of very large burns with mixed results. Keratinocyte sheet Keratinocyte colonies at various stages of cell plating Ratner BD. Biomaterials Science. San Diego: Elsevier; 2004

Permanent skin substitutes-cont’d. Analog of the Dermis as Part of a Bilayered Skin Replacement (Integra Dermal Regeneration Template, Integra LifeSciences, Inc.) Outer silastic layer (~0.1 mm) provides bacterial barrier needed while maintaining the proper water flux through the membrane, and mechanical integrity. Flux through the Silastic membrane is 1 to 10 mg/cm2/hr Pore size influences degradation time Integra consists of a layer of bovine type I collagen that has been chemically modified with glycosaminoglycans and is covered with an adherent layer of silicone Ratner BD. Biomaterials Science. San Diego: Elsevier; 2004 Prystowsky, JH. American Society of Dermatologic Sur. 2001; 27:648-655

Permanent skin substitutes-cont’d. Acellular Allogeneic Dermis (AlloDerm, LifeCell, Inc.) Allogeneic epidermis is removed and discarded from the caveder skin. The resulting acellular dermis has no cells but collagen and elastin fibers, proteins of the basement membrane such as laminin, and collagen types IV and VII. AlloDerm Acellular Allogenic Dermis Freeze-drying under controlled conditions Prior to use, acellular dermis is rehydrated in normal saline, becomes soft and pliable. Ratner BD. Biomaterials Science. San Diego: Elsevier; 2004 http://emedicine.medscape.com/article/879007-overview

Advances of silicone sheeting No distinct mechanism has been defined! 1) Effect of T: Slight increases in temperature can increase collagenase activity. 2) Effect of hydration and O2: Silicone elastomer sheets have high oxygen permeability. Mechanism of action of silicone elastomer sheeting is twofold: Increasing hydration and oxygen tension in the stratum corneum by limiting the escape of moisture while allowing oxygen access to the skin surface Oxygen tension stimulates angiogenesis and tissue growth. 3) Polarized Electric Charge: The negative charge within a silicone cushion causes polarization of the scar tissue and leads to scar shrinkage. Berman, B. American Society for Dermatologic Surgery, 2007, Blackwell Publishing, New Jersey

Examples from literature-1 1) Acellular porcine dermis(APD) manufacture pig skin is harvested (preserved at -70°C) porcine dermis is taken porcine dermis is treated with 1% trypcin for 1 h at 25 ºC to produce APD 2) Silicone sheeting ( MDX-4210 A/B Dow Corning) 3) Sterilization (ethyl alcohol + gamma rays) 4) Bacterial and fungal tests 5) Transplantation (on the wounds at the back of Sprague-Dawley rats) Silicone acellular porcine dermis (SAPD) Wang, HJ. Burns, 2005; 31: 991-997

Examples from literature-2 Schiestl C, Biedermann T. Pediatr Surg Int. 2011; 27:249-254

Examples from literature-2 Surgical procedure A full-thickness skin defect of 7.5x7.5 cm2 is created. Silicone chamber is transplanted and secured. The cultured skin substitıte is transplanted. The wound is covered with soft silver foam and silicone cover plate. Schiestl C, Biedermann T. Pediatr Surg Int. 2011; 27:249-254

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