Title: Novel Bio-Compatible Membranes Containing Scaffolds for Skin Tissue Repair.
Author : Nouran Ahmed Ibrahim Milad
Collection : M.Sc. Chemical
Abstract:
Tissue
engineering is a very important field in biomedical applications such as in skin
regeneration, nerves, liver, heart valves, and cartilages, etc… Accordingly, in
the present work natural biocompatible polymers such as chitosan (CS) and regenerated
cellulose prepared from cellulose acetate (CDA) are explored in order to
replace burnt or damaged skin, by cell seeding of the scaffolds prepared in a
bioreactor. Also, Gelatin (G) is examined as polymer additive.
CS is prepared from shrimp shells obtained from the local market through the
deacetylation and deproteination of chitin by concentrated NaOH solution, then
is dissolved in a suitable organic solvent either alone or blended with CDA or
G to form thin membranes which are cast by a special casting assembly by the
phase inversion technique, such that pores and/or scaffolds are created. Three
different techniques were used in the present work in which the as-cast
membrane is either cast at room temperature and coagulated in water bath at
ambient or ice-cold water temperature, or subjected to humid air
flow, or casting after inducing air bubbles in the casting solution mixture, or
mixed membrane treatments of these techniques. The two last techniques are both
simple and innovated methods developed by us in our laboratory. Variables
investigated were: type of polymer or polymers mixture, ratio of CS to CDA, type
of solvent or solvents mixture, initial polymer solution concentration,
concentration of deacetylating solution in the preparation of CS, time of
exposure to humid air flow of the as-cast membrane, and finally presence of
induced air bubbles and temperature of coagulation bath. Scanning electron
microscopic (SEM) examinations at different magnifications were conducted to
determine the morphology of the membrane surface and cross-section. It was
found that CS and CDA each alone gave suitable surfaces
with scaffolds and pores, and that the blend membrane gave a better membrane as
regards the number of pores, while CDA gave promising scaffolds with a
honeycomb structure. It was also found that the type of solvent affected the
surface morphology of the membrane and that deacetylation and deproteination with
50% NaOH solution gave a better CS membrane and that a more dilute casting
solution gave more suitable thinner membranes. In addition, examining the
effect of the time of exposure to humid air of the as-cast membrane has shown
that a 30 minutes exposure time gave a membrane with more scaffolds better than
20 minutes better than 10 minutes. Also, inducing air bubbles emphasized the
simplicity and efficacy of the technique in the production of scaffolds in the
membrane. The viscosity of the casting solutions had a great effect on the
porosity and the presence of scaffolds in the membrane matrix; in addition, it
was shown that membranes cast from higher viscosity solutions and low
temperature coagulation baths were very promising in the production of pores
and/or scaffolds within the membrane. SEM examinations conducted for the
majority of the membranes prepared under various conditions clarified that if pores
and/or scaffolds are present, they might be suitable for formation of regenerated
skin, in future work. Two patents are currently pending for the innovated
techniques of scaffolds for skin tissue repair.
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