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the Image to Enlarge
Outer surface shown.
NOTE: Presence of Pores
Biobrane on modest
stretch: surface smooth
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the Image to Enlarge
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the Image to Enlarge
Biobrane draped over
skin demonstrating transparency
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the Image to Enlarge
Trifilament threads
bonded with collagen exposed to wound (Biobrane)
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Monofilament threads
bonded with collagen peptide (Biobrane L)
B)
ASSESSMENT OF THE TEMPORARY SKIN SUBSTITUTE PROPERTIES OF BIOBRANE
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Properties:
- firm
adherence to wound
- barrier to
evaporative water loss (maintains surface fluid layer)
- avoids
desiccation
- barrier to
bacteria
- optimize
healing environment
- decreases
pain
- decrease
wound exudate
- durable,
flexible, non-toxic
- permeability
to topical antibiotics
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Adherence:
Biobrane contains a nylon fabric that
is woven from tri-filament threads and covalently bonded with collagen peptides.
The multiple filaments provide a high exposure to the wound surface resulting in
an increasing adherence to the wound surface of partial thickness burn.
Biobrane L contains a nylon fabric
woven from monofilament threads that provide a less dense matrix and less
adherence, preferred e.g. on a donor site.
Adherence is
biphasic: the initial adherence phase is due to fibrin-collagen (nylon) bonding
and the second is the ingrowth of epithelial cells and fibrin between the
threads. Adherence initially is comparable to allograft but biobrane adherence
exceeds allograft by 3-5 days. For comparisons of adherence between skin
substitutes see Section IV.
Water Vapor Transport
A decrease in water vapor transport is
essential to avoid wound desiccation. However, some water vapor permeability is
beneficial in preventing excess fluid accumulation.
Biobrane is nearly as
effective as normal skin as a water vapor barrier after day 5
(Tavis et al. A new composite skin prosthesis. Burn 1978: 7; 1283.
Barrier to Bacteria
Assessment performed by surface
cultures of wounds excised and covered with biobrane, allograft or treated open.
In this study
Biobrane was more effective than allograft as a bacterial barrier Tavis et al.
A new composite skin prosthesis. Burns 1978: 7; 1233.
- Optimizing healing environment
(comparative studies in section E
demonstrate biobrane to increase re-epithelialization rate compared to topical
antibiotics or exeroform gauze
(comparative studies in section E
demonstrate biobrane to decrease pain compared to topical antibiotics or
xeroform gauze
(comparative studies demonstrate
biobrane to decrease exudate compared to fine mesh gauze
a minimal elongation of 350± 50% and a
burst strength of 10.3± 2 lb/inch have been reported (Tavis, et al)
Permeability to antibiotics
Permeability to 1% silver
Sulfadiazine comparing biobrane without pores to the standard with pores. The
standard biobrane is very permeable to topical antibiotics. (Tavis et.al.)
- the
value for the primary skin irritation index falls within the
"non-irritant" category
- intracutaneous toxicity studies were
reportedly negative
- pyrogenicity studies were reported
negative
C) MECHANISM OF
ACTION
The mechanism of action is initially
described using schemas to be followed by clinical application.
Biobrane bilayer
structure is shown. The silicone outer layer acts like a protective epidermal
barrier. The inner surface composed of a three dimensional interwoven nylon
filament structure upon which collagen peptides are boarded. Initial wound
adherence is the result of bonding of the inner membrane collagen coated nylon
to surface fibrin. The second phase of increasing adherence results from
epidermal cells migrating and proliferating between the nylon matrix.
A superficial partial
thickness burn is shown. The zone of necrosis is confined to the upper
(papillary) dermis and is usually separated by a layer of edema from the viable
wound surface. Note the zone of injury which needs to be protected.
Superficial burn
debrided to viable wound bed. Note surface fibrin and collagen. Also note
increased proteolytic activity which is not suppressed by immediate wound
closure, will produce increased injury.
Bilayer biobrane
ready to be placed on clean wound. Note outer silicone layer (epidermal analog)
and inner nylon mesh coated with collagen to adhere to surface (dermal analog)
Biobrane in place,
adhered to surface by nylon-collagen mesh. Note preservation of thin water layer
on surface to allow epithelial migration along inner layer.
Biobrane peeled back
from surface to demonstrate rapid migration of new epithelium along
nylon-collagen mesh. As epithelialization increases the biobrane becomes more
opaque. The minimal exudate produced, drains out the pores.
Biobrane removed with
re-epithelialization.
