Team:METU-Gene/Gelatin Sponge

<br>It is believed that, epidermal growth factor (EGF) stimulates the growth of keratinocytes in vivo, and therefore plays an important role in the process of wound healing that depends on mitosis and migration of keratinocytes. Rhinewald and Green showed, in vitro that in the presence of growth factors, higher percentage of cells leave the resting state, enter and remain in the mitotic cycle [23]. Assuming a similar e!ect of EGF on epidermal cells in vivo, the primary mechanism of enhanced wound healing is most likely due to increased proliferation of epidermal cells.

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<h2>EGF's effects</h2>
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<p style="font-size:110%; color:#576f91; font-family:georgia,serif;">Mitogenic effect of EGF requires continuous exposure of
target cells to EGF for a minimum 6-12 h.The stimulation of wound healing by EGF has been
confirmed by Laato et al. as growth of granulation tissue
in sponge implants used as inductive matrices [33].Buckley et al. reported that
sustained release of EGF from subcutaneous pellets accelerated
process of wound repair in rats, whereas daily
injections of EGF were much less e!ective [30].</p>

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<h2>Layer Usage</h2>
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<p style="font-size:110%; color:#576f91; font-family:georgia,serif;">The half-life of EGF in the body is,
however, too short to exert the biological activity e!ectively
when applied via injection or in free form. It is
known that many proteases are activated in the injured
tissue and they easily decompose EGF in the wounded or
burned site of skin as soon as it is applied as an ointment
[36].'''Therefore, our biomaterial grade sponge has protease inhibitor feature.''' A porous and biodegradable matrix that would serve as
the host for the proliferating cells and would degrade
spontaneously without creating any adverse effects while
the tissue regenerates was planned to act as the underlying
dermal layer.Thus,with biodegredation of sponge,EGF and KGF will be able to pass through the layer easily. </p>

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<h2>Discussion onto Material</h2>
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<p style="font-size:110%; color:#576f91; font-family:georgia,serif;">Polyurethane membranes were used as the external
layer because of their biocompatibility and hemocompatibility.
Besides they are highly elastomeric (extensible)
and permeable to gaseous substances. They create an
inert environment for the blood, control water and heat
transfer through the wound area, and prevent bacterial
invasion. They are mechanically strong and protect the
wound from the external effects [37}42].
Gelatin was chosen as the porous soft layer material.
Since it is practically more convenient than collagen and
known to have no antigenicity while collagen expresses
some in physiological conditions. Also, it is extremely
di$cult to prepare concentrated solutions of native collagen.
Furthermore, gelatin is far more economical than
collagen. The soft and porous gelatin sponges beneath
the polyurethane films would have direct contact with
the tissue and expected not to cause any damage to the
wound area. Because of their high absorptive capacity
they would prevent fluid accumulation. Therefore, excess
water (exudate composed of wound fluids) and cell debris
would be absorbed and retained inside the sponges. Tissue
ingrowth would take place in the matrix and the
regenerating wound tissue and implant would not be
separated. The sponge is biodegradable, therefore, it
would degrade and be replaced by the newly regenerated
tissue. </p>

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