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الثلاثاء، 5 أغسطس، 2014

Novel Bio-Compatible Membranes Containing Scaffolds for Skin Tissue Repair.

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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