Sharif Digital Repository

This thesis focuses on the preparation and super-swelling behavior of a superabsorbent hydrogel based on natural macro-molecules and loading potassium nitrite as an agro-chemical onto it. 1-In this investigation a new type of superabsorbent hydrogel based on Gelatin and k-Carrageenan was prepared and the effect of the feed ratio of some components (acrylic acid, MBA, APS, and agar) on the swelling capacity of the hydrogel was systematically studied. The structure of the hydrogel optimized final product was found to be 1064 g/g in distilled water. The structure of the hydrogel was characterized by FT_IR method and morphology of the samples was examined by scamming electron microscopy (SEM).... 

This thesis focuses on the preparation and super-swelling behavior of four highly porous hydrogels: 1. Firstly, we have developed a collagen-based highly porous hydrogel by neutralizing the grafted poly(acrylamide-co-acrylic acid) after gel formation. Systematically, the certain variables of the graft copolymerization were optimized to achieve maximum swelling capacity. Morphology of the samples was examined by scanning electron microscopy (SEM) and was shown the pores were induced into the hydrogel by water evaporation resulting from neutralization process. The absorbency under load (AUL) and centrifuge retention capacity (CRC) were measured. The synthesized hydrogel exhibited a... 

Maghemite (γ-Fe2O3) nanoparticles were produced after high temperature oxidation of gelatin-Fe3O4 nanocomposite, obtained from a common coprecipitation process of Fe2+ and Fe3+ ions in an alkaline medium in the presence of a gelatin protein as an effective mediator. Size, shape, surface morphology and magnetic properties of the prepared γ-Fe2O3 nanoparticles were characterized using XRD, FTIR, TEM, SEM and VSM data. The results revealed that primary, gelatin-Fe3O4 nanocomposite had been formed and next, the gelatin decomposition in furnace produced a spinel structure of γ-Fe2O3. The effects of furnace temperature and time of heating together with the amount of gelatin on the produced... 

Peppermint oil is one of the most often used food ingredients and it is volatile. Many common procedures such as microencapsulation have been used for protecting volatile food ingredients. For this research, L-menthol was chosen as the core material to be encapsulated. L-menthol is responsible for the minty flavor and cooling sensation of food and pharmaceutical products. The encapsulation of L-menthol was prepared by complex coacervation, using gum Arabic and gelatin as wall material and tannic acid as cross-linking agent. The effect of various processing parameters, including wall material, core material, tannic acid and tween¬80 concentrations, on particle size and efficiency was... 

Generally, the concept of producing ‘spare parts’ of the body for replacement of damaged or lost organs lies at the core of the varied biotechnological practices referred as tissue engineering. Tissue engineering is an interdisciplinary field that incorporates principles of engineering with the life sciences. Tissue engineering is based on three principle; cells, scaffolds for cells expansion, attachment as an environment like ECM and growth factors. These things together can help tissue engineers to provide microenvironments which are suitable for special cells. The most important thing in this kind of works is the ability to simulate environment for cells the same as body. According to the... 

Silver nanoparticles (Ag-NPs) are promising agents in bionanotechnology, because of their unique activity against unfavorable processes in bioscience such as undesirable microbial growth, angiogenesis in tumors and etc. Ag-NPs have been widely used in wound dressing; wound healing, water treatment filters, inks, sensors, catalysts, cosmetics, orthopaedics, surgical instruments and vascular prosthesis. Ever-increasing applications of Ag-NPs in biomedical field are due to the anti-bacterial, anti-fungal, anti-viral, anti-platelet, anti-proliferative, anti-inflammatory (apoptosis detection) and anti-angiogenesis properties (cancer therapy). In the current research, we synthesized Ag-NPs in... 

Hydrogels are polymeric three-dimensional networks able to swell in the presence of an aqueous medium. Hydrogels from natural proteins and polysaccharides are ideal scaffolds for tissue engineering since they resemble the extracellular matrices of tissue comprised of various amino acids and sugar-based macromolecules.The biocompatible and biodegradable hydrogel scaffolds are promising materials for tissue engineering. Here, we report a new class of hydrogels derived from oxidized alginate (OA) and gelatin. The prepared oxidized alginate was shown to be efficient in crosslinking gelatin, leading to hydrogel formation. The effect of degree of oxidation and concentration of OA on the mechanical... 

The present study is work on fabrication and characterization of a chitosan/ gelatin/ Mg substituted hydroxyapatite nano composite scaffold for bone tissue engineering. At the first step pure and Mg-substituted hydroxyapatite (HA) (Ca10-xMgx(PO4) 6OH2) nano-hexagonal rods with 14–45 nmdiameter.for this, calcium nitrate, magnesium phosphate hydrate and potassium dihydrogenphosphate were used as precursors for Ca, Mg, and P, respectively. Calculated amounts of magnesium ions (Mg+2) especially from 0 to 8% (molar ratio) were incorporated as substituted into the calcium sol solution. Deionized water was used as a diluting media for HA sol preparation and ammonia was used to adjust the pH= 9.... 

In present work, hydroxyapatite nano-rods are synthesized using a simple sol-gel method with calcium nitrate and potassium dihydrogenphosphate as calcium and phosphorus precursors respectively and ammonia was used for adjusting the pH=9. To obtain rod shape hydroxyapaite powder, multi wall carbon nanotubes were added to the solution, nHA powder was calcinated at 60 and 450 ℃. In second step, chitosan-gelatin/nanoHA solution were prepared by blending chitosan and gelatin in different concentrations with nanoHA powder, then the solution was freeze dried to maintain a composite scaffold. The prepared HA powder and bio-composite scaffold were characterized by X-ray diffraction (XRD), field... 

Biocompatible porous polymeric scaffolds provide a suitable 3-D environment for proliferation of stem cells in human body. For instance, growth and proliferation concurrent with differentiation of stem cells in such scaffolds can regenerate the tissues or organs. In this attitude we fabricated a porous Gelatin-based scaffold using both of freeze-drying and freeze-extraction methods.Also, effect fo gamma irradiation on microstructure of scaffolds was investigated. In addition, poly(ethylene glycol) was employed to make the scaffold softer. Moreover, effects of various parameters including freezing temperature, cross-linking agent concentration, gelatin and PEG concentrations and their... 

Microcarriers (MCs) are an attractive technology with various applications in tissue engineering. In this study, chitosan/gelatin MCs were fabricated with blends of different ratio of chitosan/gelatin, by using a setup containing high voltage electrostatic field and syringe pump. Optimization of blend ratio, voltage and syringe pump flow carried out by the “Design expert” software leads to fabrication of MCs with constant diameter while having various elasticity. Mechanical strength and elasticity of MCs were determined. Human umbilical cord mesenchymal stem cells (hUCMSCs) were cultured on MCs dynamically by using mini-rocher in an incubator. Cells adhesion on MCs were successfully shown by... 

The goal of this research project was to prepare gelatin/PVA porous scaffolds by chemical and gamma irradiation methods to be used for human dermal fibroblast cell culture. First, the polymers were dissolved in hot water and mixed properly to achieve a homogenous solution. The mixture was then frozen at -200C and immersed in ethanol/ glutaraldehyde solution at -200C for 48 hours in order to extract ice crystals and also form chemical crosslinks in gelatin by glutaraldehyde. After being rinsed with distilled water the samples were lyophilized. The effects of polymers solution concentration, gelatin/PVA ratio and glutaraldehyde /gelatin ratio were investigated on characteristics of the... 

Vitamin C is one of the essential ingredients for the survival of human beings, animals and plants. This vitamin is an ester that in its structure there is a cyclic ester, an alkene Factor (C = C) and four hydroxyl factor (OH). This vitamin is a white solid, water-soluble and non-toxic that exists in many fruits, especially citrus. Its presence in the diet of human resistance them against infections increases. The main factor causing acidic property in vitamin C is the presence of OH groups attached to the alkene. Various forms of vitamin C exists in pharmaceutical collection of European countries. Since the tablet form because of the many advantages including being economical compared with... 

In this study, gelatin/polyvinylpyrrolidone semi interpenetrating polymer network scaffold was synthesized in presence of glutaraldehyde as a cross linker and a porous structure was obtained by freeze drying method. The biocompatible network with properties like huge porosity, good thermal stability and establishing different interactions, was employed as an extractive phase in needle trap device and used for evaluation of benzene, toluene, ethylbenzene and xylene (BTEX) in conjugation with gas chromatography-flame ionization detector. For investigating semi interpenetrating polymer network efficiency, Different ratios of gelatin and polyvinylpyrrolidone (gelatin/polyvinylpyrrolidone: 1:0,... 

Neural system in human body due to limitated cell proliferation requires high care, because the damage causes serious hurts and disables different tissues. Limit regeneration in central neural system can cause different neural diseases including brain exhaustions specially in old people, but the peripheral neural system may have been disabled and intrupt some other tissue beacuase of possible external injuries before aging. So that while some damages like neural fibers severing, some new medical care methods are required. Some of these methods are outograft, allograft and xenograft which implants neural tissues either between other patient's tissues or from somebody else's; however these... 

Articular cartilage has limited repair capability following traumatic injuries and current methods of treatment remain inefficient. Reconstructing cartilage provides a new way for cartilage repair and natural polymers are often used as scaffold because of their biocompatibility and biofunctionality. The goal of cartilage tissue engineering is to design a scaffold with proper pore structure and similar mechanical properties to the native tissue. In this study Porous scaffolds prepared from silk fibroin, chitosan and gelatin blends with varying ratio of silk fibroin and gelatin by freeze drying method were characterized for physicochemical, mechanical and biological properties. Among the... 

Cardiovascular diseases are among the leading causes of death worldwide. For instance, in 2015, almost 31% of the world’s mortality rate was due to these causes. One of these diseases is cardiac coronary vessels’ occlusion which leads to the insufficient blood supply to the heart tissue and cardiomyocytes death after Myocardial Infarction (MI). After MI, a hierarchy of events in the heart tissue changes heart muscle and forms cardiac fibrosis. This fibrotic tissue does not have the native one’s properties and function, so it will cause cardiac arrest and patient death. Therefore, it is obvious that vascular network plays a crucial role in the heart function. The importance of cardiac... 

Due to the increased public awareness about the role of food on health, an increased interest of consuming fortified food has grown rapidly. Probiotic bacteria and DHA poly-unsaturated fatty acid are two major bioactive ingredients becoming increasingly popular in food fortification industry due to their beneficial effects. However, high susceptibility of probiotic bacteria during production, maintenance and digestion in acidic and enzymatic conditions of gastrointestinal tract results in decreasing the survivability and therefore reducing health effects in body. Besides, having multiple double bonds in the structure of DHA fatty acid leads to oxidative degradation that produces volatile... 

Making artificial skin and skin alternatives is one of the most important areas in tissue engineering. Although much progress has been made so far, there is still no definitive cure for second- and third-degree burns. To create new tissue in the body, a suitable substrate for cells is needed, which is called scaffolding, and an ideal scaffold in tissue engineering should mimic the dimensions of extracellular matrix, and nanofibers seem to be the best option for this purpose. Among the methods of manufacturing of nanofibers, electrospun is very easy and accurate method. In previous studies, many natural and synthetic polymers such as chitosan, alginate, collagen, polyathylene oxide, etc.... 

In recent years, it is expected that the fabrication of multilayer scaffolds and the use of different methodologies in one product can be a new progressing method in skin substitute production. Accordingly, this project aims to fabricate a bilayered composite scaffold with a combination of hydrogel and electrospinning method. We have tried to prepare a scaffold made of oxidized alginate (OAL), gelatin (G), and silk fibroin (SF) without using corrosive solvents and toxic crosslinking agents as a scaffold and drug delivery system. As different biological, chemical, physical, and mechanical factors play a vital role in the healing process, we have characterized the proposed scaffold via DSC,...