الفهرس 
Cover Page Title in EnglishOnly 14 pages are availabe for public view
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Abstract
Thousands of patients need to graft or repair their skin to compensate skin loss due to injuries, burns, etc. An appropriate recent approach (Nanotechnology) is aimed to develop tissue engineered materials to be used as wound dressings for wound healing and skin regeneration purposes. The aim of the presented study is to fabricate bioengineered scaffold which similar to extracellular matrix (ECM) to provide high biocompatibility and biodegradability wound dressing to support healthy and high-quality healed skin. So, nanofiber mat was prepared by simple technique called electrospinning, by using synthetic polymer (Polyvinyl alcohol) which provide the mechanical stability of the membrane but has low cell adhesion prosperity due to low protein affinity, so it was blended with natural polymer (gelatin), which provide the high cellular affinity due to the arginine-glycine-aspartic acid (RGD) integrin-binding sequence. The prepared mat was characterized by using Scanning electron microscope to evaluate their morphology and by using Fourier transform infrared spectroscopy to evaluate their chemical structure. Polyvinyl alcohol (PVA) dissolved in water which explain their wide use in medical application instead of using other toxic solvents, in the present study there was gradual increase in the concentration of the prepared PVA solution which positively correlated with the solution viscosity from (15%) until reach to the optimum concentration (30%) in which capable to produce continuous jet which formed uniform smooth non- beaded nanofibers, which simulate the morphology of ECM as it is known that The behavior of cells, including cell adhesion, morphology, proliferation, and differentiation, is affected by surface topography. Blending with PVA with gelatin was observed that it improved the nanofiber morphology but reduced the solution viscosity which lead to decrease in the diameters of the prepared electrospun nanofiber blend (PVA 30% - gelatin 10%) Antimicrobial nanofiber mat was prepared by loading of silver nanoparticles (SNPs) which prepared by using chemical reduction of silver nitrate salts then by the high-power supply in electrospinning helped in more reduction of the rest of un reduced silver ions. The prepared nanofiber mat was tested for their biocompatibility, biodegradability and their efficient antimicrobial effect on wound healing by in vivo application in rabbit model with full thickness skin defect. Ten New Zeeland rabbits were used in the present study to induce full-thickness excisional skin defect, two wound defects were made on the dorsum of the animals with accurate well-defined diameters (3x3cm2) with sharp incision and removal of the panniculus muscle with corner wound fixation in order to control healing by contraction. All animals were divided randomly into 2 groups (n = 2 full-thickness wound /5animals in each group), Group(1) : Negative control group (no treatment), Plain Nanofiber mat application, group (2): Positive control (SNPs topical application with their solution form), and Nanofiber loaded with SNPs (Antimicrobial mat) Clinical (Macroscopic) evaluation of wound healing was made through the healing process in (7th ,14th, 21st days) and it was observed not only accelerating of the wound closure with N.F groups but also improved the quality of the healed skin to be somehow similar to the normal skin with developed skin appendages and it was observed the significant reduction of the infection in the SNPs groups in compare with control group, which demonstrated the anti-microbial effect of SNPs. Histopathological (Microscopic) evaluation was also done at 2nd and 3rd week samples were taken to examine the healing quality by H&E staining that showed a similar phenotype to normal skin with better wound bed re-organization with N.F/SNPs group and well defined epidermal layer formation with N.F and SNPs groups. The rate of collagen deposition, was examined by using Masson Trichrome staining, in which the control group showed very poor collagen deposition while in the 3 other groups showed well-oriented granulation tissues formation. Conclusion The conclusion of this study was summarized in: 1. Fabrication of Nanofiber mat was done by blend polyvinyl alcohol (30%) with gelatin (10%), which in this concentration showed the highly uniformed non-beaded smooth fiber which characterized their morphology by scanning electron microscope with diameters ranged from (40-90 nm). 2. Loading of the nanofiber with antimicrobial agent (Silver nanoparticles) was successfully done by chemical reduction of silver nitrate salts and characterized by U.V absorbance spectroscopy, by sharp peak observed at 430nm, which confirm nanoparticle formation. 3. Experimental wound induction was successfully made on the rabbit dorsum with well-defined diameters (3x3cm2), precautions were taken to control healing by contraction force through removal of panniculus carnuious muscle and corner stitch fixation of the wound, which contributed significantly in more accurate outcomes. 4. Application of the nanofiber mats was done in comparison with control groups (negative and positive), the macroscopic assessment confirmed the antimicrobial effect of silver nanoparticle effect in which significant reduction in the infection rate in comparison with the control group. The improved quality of the healed skin in the N.Fs groups confirm the capability NFs mats to play the scaffold role in skin regeneration.
Future Aspects: Long -term observation need to be done to assess the tensile strength of the healed skin, and more researches need to control the healing by contraction to improve the rabbit model to represent other healing processes. Also, more studies needed to evaluate the drug release from the nanofiber ma