Biomedical Engineering Reference
In-Depth Information
epidermal layers, achieve favorable functional and cosmetic outcome, be free from
risk of disease transmission and have minimal immunological reaction, with the
ultimate goal of wound closure with the elimination or reduction of a donor site for
skin grafts. If these objectives are satisfied, recovery time should hypothetically be
reduced and operative procedure reduced.
Delivery of cultured cells to wounds can be facilitated by combination with a
biopolymer scaffold. Skin substitutes have been prepared utilizing synthetic
polymers such as polylactic/polyglycolic acid (PLGA),
20
polyglycolic acid
(PGA),
21
polycaprolactone (PCL)
22
and polystyrene,
23
natural polymers like col-
lagen
24
or composite synthetic-natural polymers such as PCL-collagen.
22
In
addition, naturally derived matrices including decellularized extracellular ma-
trix,
25
small intestinal submucosa (SIS)
26
and human fibroblast produced matrix
27
have been studied as a matrix for skin regeneration. Fundamental considerations
for biopolymer scaffolds for cell delivery include rate of degradation,
immunogenicity/biocompatibility, mass transfer rates (fluid flux) and mechani-
cal properties.
The surgical requirements of skin substitutes are well understood and include
rapid adherence, decrease in fluid and electrolyte loss, control of pain, protection
against microbial colonization and proliferation, promotion of healing, durability
and flexibility, sterility, absence of toxicity, low immunogenicity, cost effective-
ness and high availability.
28-30
Clinical complications with engineered skin result
predominantly from anatomic and physiologic deficiencies that compromise
responses to the wound healing process.
12.3
Design and composition of cultured skin
substitutes
Basic design considerations for replacement skin include control of infection,
fluid loss, contracture and scarring, but are only a part of a large set of require-
ments including rapid adherence and vascularization, mechanical stability and
durability and cost-effectiveness. Restoration of skin anatomy includes not only
the epidermis and dermis but also skin pigmentation, nerve, vascular plexus and
adnexa (glands and follicles). Many skin analogues have been developed
23,31-35
yet none has duplicated
in vitro
all of the structures and functions of native
human skin. Cultured skin substitutes are composed of collagen-
glycosaminoglycan (GAG) substrates containing autologous fibroblasts and
keratinocytes and provide permanent replacement of both dermal and epidermal
for the deconstruction of a skin biopsy into its constituent cells and reconstruc-
tion of the cultured skin substitute from cells expanded from the initial biopsy
and a biopolymer substrate.
