Sharif Digital Repository

Polyampholyte hydrogels are hydrophilic networks that contain both positively- and negatively-charged functional groups on their structure. Polysulfobetaines are the most important type of polyampholytes, which have been extensively studied. However, these hydrogels exhibited poor gel strength causing limitation of their applications. Consequently, much attention has been focused on the preparation of nanocomposite hydrogels with high gel strength and lower cost using organomodified clays. In this project, Novel polyampholytic superabsorbing nanocomposites based on the zwitterionic sulfobetaine monomer [3-(methacrylamido)propyl)]dimethyl(3-sulfopropyl) ammonium hydroxide (MPDSAH) were... 

This thesis focouses on the preparation and super-swelling behavior of two superabsorbent hydrogel. In the first section, a new superabsorbent hydrogel based on agar was prepared and the effect of the ratio of some components(AA, AAM, MBA, APS and agar) on the swelling capasity of the hydrogel was studied. Maximum water absorbency of the optimized final product was found to be 614.5 g/g in distilled water. The structure of the hydrogel was characterized by FT-IR method and morphology of the samples was examined by scanning electron microscopy(SEM). Swelling behavior properties of optimized hydrogel sample in different swelling medium were investigated. In the second section, we report the... 

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).... 

Poly (vinyl alcohol) (PVA) hydrogel is a biocompatible material, which has been widely applied in drug delivery applications. Microspheres, nanospheres, and other types of particle-based drug delivery vehicles have proven capacity for long-term release. There is growing interest to overcoming the inherent pharmacological limitations of hydrogels by formulating particulate systems into the hydrogel matrix to form new delivery platforms. We here describe a simple composite system based on poly (vinyl alcohol) (PVA) hydrogels containing entrapped drug-loaded poly (lactic acid) (PLA) microspheres for controlled delivery over extended period of time. Gamma-Irradiation and freeze-thawing was... 

Hemophilia is a group of hereditary genetic disorders that impair the body's ability to control blood clotting due to the lack of coagulation factors. Frequent joint and soft tissue bleeding is one the most common problems amongst these patients which can become progressively destructive for cartilage tissue in case of the late treatment. In this work, injectable PEG-based hydrogel nanocomposites with mechanical and structural properties close to cartilage tissue were fabricated. First, primary copolymers with PEG blocks of 600 g.mol-1 and 900 g.mol-1 without and with 2.5 wt.% Laponite nanoclay were synthesized by two-step thermal poly (amic acid) process. After polymer purification,... 

Polyvinylalcohol/MWCNT nanocomposite films were fabricated via solution casting method. Glycerol was added to the polymer matrix as plasticizer in order to improve the flexibility and toughness of resultant films. Surface modification of MWCNTs were carried out by subjecting to gamma irradiation of 60Co source to total doses of 50.0 and 75 kGy in pure ethanol and in a solution with equal volume fraction of water and ethanol. The produced nanocomposites in each case which contain different type of modified MWCNTs were characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), mechanical and electrical measurements. The... 

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... 

Poly vinyl alcohol/graphene oxide (GO) nanocomposites were made through solution casting method. The nanocomposite were characterized by XRD , FTIR , FESEM , DSC and mechanical measurements. Graphene oxide was irradiated by gamma ray at 35 KGy in a 50/50 water-ethanol solution and then added to PVA aqueous solution in various GO concentrations (0.3 , 0.7 , 1 wt%) and sonicated. The resulting suspensions were cast into petri dishes to make thin films. Also PVA/GO Hydrogels were prepared by gamma irradiation at 20 KGy. It was observed that GO uniformly dispersed within PVA indicating strong interaction through forming hydrogen bonds between hydroxyl groups of PVA and GO surface. Tensile... 

In this work, the mechanical behavior of smart hydrogels is studied for temperature sensitive and, pH and temperature sensitive ones. First, an equilibrium model is presented for the temperature sensitive hydrogles which is continuous and numerically stable especially in the vicinity of the phase transition temperature. The model results are validated through comparing them with the experimental data available in the literature. The model results are in good agreement with those of experiments especially for hydrogels with high cross-linking density. Then, the model is implemented in a finite element framework by which some homogeneous and inhomogeneous problems are numerically solved.... 

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... 

Graphene، a molecular single layer of graphite، has tremendous applications in materials science for the development of nanocomposites، tissue engineering and supercapacitors. Graphene application and its developing applications depend on its essential properties such as excellent mechanical and thermal properties. Accordingly، investigation on graphene has drawn significant attention to itself. Hence، exploitation of these important properties including the induction of graphene sheets in polymer matrix seems to be essential. In the present survey، salep، a biodegradable polysaccharide، has been used for either the reduction of graphene oxide or functionalization of graphene. Then، reduced... 

Cardiovascular disease is responsible for a majority of health problem in developing countries. Heart diseases are the leading cause of death in the United State with approximately 40% of the death occurs by heart failures and coronary artery defects. Myocardial infarction is one of the diseases that occurs by coronay artery blockage. Cardiac tissue engineering (CTE) is an emerging field that holds great promise towards the development of innovative treatment strategies for heart disease. There are two common scaffolds for CTE, electrospun fiber mats and hydrogels. Although fibers are known as 3D environment for cells, they actually act as a 2D surface, because of lack of cell infilteration.... 

Double network (DN) hydrogels are a new interpenetrate polymer network (IPN) that are usually contain about 60-90 % water. Despite of this amount of water, they are though and strong. DN hydrogels comprise of two networks, the first one as the brittle gel, is generally high density crosslinked and the second one, the loose and stretchable network, is loosely crosslinked or even without crosslinking. Therefore, we used cationic polymer, chitosan, and anionic polymer, alginate, as the first networks, therefore, we used sodium phosphate for physical crosslinking of chitosan, and calcium chloride as the physical crosslinking agents for alginate network. Also, poly (vinyl alcohol) (PVA), as the... 

A novel thermo responsive decorated system is designed by coating Fe3O4 magnetic nanoparticles with conjugated Pluronic-ATPEG copolymer incorporated into the PEG-PMDA Hydrogel for drug delivery to the cartilage tissue. Grafted copolymer was synthesized by reaction between carboxylated Pluronic and amino terminated Poly ethylene glycol (ATPEG) and confirmed by FTIR and NMR analysis. The magnetic nanoparticles were modified with the produced copolymer and characterized by TEM, HRTEM, XRD, DLS, and VSM. A typical product has 13 nm magnetic core and 105 nm hydrodynamic diameter with narrow size distribution. DLS results showed that there was an increase in size by increasing temperature from 25℃... 

The nucleus pulposus, which is a part of intervertebral disc, is normally hydrated and gel-like to maintain normal biomechanical functions of the disc through intradiscal pressures. In a degenerated disc, however, water content of nucleus is significantly reduced, resulting in an abnormal stress state of the annulus. Surgical interventions cannot restore the biomedical function to vertebral segment. One approach to restore the normal biomechanics of an intervertebral disc is to replace the nucleus with a prosthetic material which leads to a restoration of the behavior of the disc. The mechanical behavior of poly(vinyl alcohol) and nanodiamond hydrogel may provide a material suitable for... 

Wound is a defect or failure in the skin texture which occurs as a result of physical or heat injuries or physiological conditions. The wound dress as a temporary cover can improve wound healing process and due to the unique properties, hydrogels have become appropriate choice for this application. Hydrogel’s structure allows drug to be loaded in the wound dress. Hydrogel wound dress should have adequate fluidity to cover wound’s bed and make full contact with the skin. Sufficient cohesion and strength is also necessary to allow the wound dress to remove from wound completely. Therefore, the study on the viscoelastic properties of hydrogel is important. In this study, polyvinyl alcohol... 

In this work, wool keratin/polyethylene oxide (PEO) nanofibrous scaffolds were fabricated by electrospinning method. Bacterial cellulose nanofibrils (BCNFs) were embedded in the electrospun keratin/PEO nanofibers. Incorporation of BCNFs into the nanofibers enhances their hydrophilicity, mechanical properties and cell viability, adhesion and proliferation. Water contact angle of the nanofibers decreased from 126˚ to 83˚by addition of 1 wt % BCNFs. A thermogelling hydrogel based on carboxylated pluronic (Pl-COOH) and gum tragacanth (GT) was fabricated and polymer conjugation was confirmed by FTIR and H-NMR spectroscopy. Morphological and viscoelastic properties of GT-grafted Pl-COOH hydrogels... 

Methods that has been used for articular defects are faced with many limitations, so new therapies based on tissue engineering were taken into consideration in recent years. However, tissue engineering also encounters challenges regarding optimal scaffold construction and suitable cell source selection. Mature harvested chondrocytes are limited in number and may lose their chondrogenic potential in several cultures, leading to dedifferentiation. In addition, using stem cells also presents unique challenges associated with them, among which hypertrophic differentiation is the most substantial problem. Choosing the appropriate biomaterial similar to the cartilage structure with sufficient... 

Hydrogels are crosslinked hydrophilic polymers that are capable of imbedding large amounts of water or biological fluids usually to equilibrium. Because of their unique properties, these materials have become ubiquitous and indispensable materials in many applications in recent years. Synthetic methods have produced numerous hydrogel materials with excellent properties. However, their nonbiodegradability might pose long-term environmental problems and limit their use. As a consequence, various research groups have put considerable amounts of effort and resources toward development of new absorbent materials from natural polymers such as polysaccharides. In this research, new hydrogel... 

Lately, a wide application of eco-friendly polysaccharide-based hydrogels in waste water treatment has received enormous attention in the literature. The effluents containing dye materials from the processing industries are washed off into rivers and lakes which can be very harmful to creatures. Low-cost biopolymers and biodegradable adsorbents have been researched to be a good tool to minimize the environmental hazards caused by the industrial effluents by removal of these toxic and carcinogenic dyes from the waste effluents. In this study, an eco-friendly superabsorbent hydrogel was prepared by using of sugarcane bagasse, two hydrophilic monomers, magnetic nanoparticle and methylene...