1. WOUND DRESSINGS
SPRING 2012
MASE542
Çağla Koşak

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

3. 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:

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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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:

16. 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

17. 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

18. 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:

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

20. 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:

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