Sharif Digital Repository

In this project, a novel system of bioactive electrospun scaffold for bladder tissue engineering , has been investigated to control in vitro cell differentiation, and utilize in in vivo vascularization and tissue formation. This method doesn’t have custom bioactive scaffolds problems such as, protein instability, technical complexity and, difficulties in accurate kinetics prediction. First of all, protein loaded chitosan nanoparticles based on ionic gelation interaction between chitosan and Sodium tripolyphosphate were prepared. Maximum protein loading efficiency (80% for BSA & 99% for TGF-beta1) in chitosan nanoparticles was obtained at mean diameter of 51nm. Moreover polycaprolactone... 

In this research we focus on study and fabrication of one dimentianal TiO2 nanostructures and nanoheterostructures on TiO2 nanofibers in order to use them in Dye Sensitized Solar Cells (DSC). Nanofibers of titanium oxide have been fabricated using hydrothermal method. Then, hierarchical TiO2 nanostructures were grown on the nanofibers via another hydrothermal step. Increasing the effective surface of nanofibers, we achieved two secondary architectures from fibers:1-Nanoparticular fibers (TiO2 nanoparticles grown on nanofibers).2-Nanostars.After fabrication, the SEM and XRD characterizations were provided. Furthermore, the suitable pastes of these nanostructures were prepared for application... 

Since previous models can not give a complete description for electrospinning electrical instability, using polymer solutions with diifferent properties, the aim of the existing thesis is to propose a new model that covers a range of materials from non-conducting to conducting and from viscous to elastic and also the initial jet’s tension. In addition, since the previous models have used large wave length approxiamtions, using accurate calculations we showed that the new model has better results for small wavelengths of about two times the jet’s radii. To compare the model to experimental results, we designed and made a proper setup to record the electrospinning process for a PEO solution... 

Preparation and application of nanostructured sorbents for microextraction of some environmental pollutants and pesticides are the bases of this research. The first part of thesis deals with carbon nanotubes (CNTs) and their relevant nanocomposites using silica and conductive polymer matrix as extracting media. While, the second part involves the preparation of nanofibers and nanowires and they were applied for extraction of some selected pesticide from aquatic samples.
In the first work of part one, CNTs chemically bonded on modified gold substrate was used as novel unbreakable solid phase microextraction fiber for isolation of diazinon and fenthion, as model compounds. Parameters... 

The aim of the current project is preparation, characterization and microfiltration evaluation of nanofiberous membrane. In order to prepare membranes, the electrospinning method was utilized and polyacrylonitrile and N-N, dimethylformamide (DMF) were used as the polymer and the solvent, respectively. As the nanofiber diameter controls the structure of the membrane and also bead formation reduces the membrane uniformity, at first the effects of four most influential electrospinning parameters, such as solution concentration, applied voltage, floe rate, and the distance between needle tip and the collector, on average fiber diameter and bead area density were investigated via response surface... 

In this research, the synthesis of the electrospum nano fiber doped zinc oxide and its photocatalyst usage was investigated. The band gap of the zinc oxide in the area of UV leads to deactivation of this material at the visible light. With due the attention to sunny weather in Iran and the fact that about 50 percentage of sunlight is visible light, producing and usage of catalyst materials actived at visible light is economical. Doping is one of the ways of activating ZnO at visible light, so in this research thiourea is used as the source of ZnO doping. The results of the expriments done at visible light and also spectrums of DRS, XPS and XRD prove that the doping is happened. Also, in this... 

In this thesis we present fabrication, characterization, and experimental results describing electrical actuation and readout of the mechanical vibratory response of PVP, graphene-doped and ZnO fibers by employing electrical actuation. For a fiber resonator with an approximate radius of 850 nm and length of 100 µm, we observed a resonance frequency around 580 kHz with a quality factor (Q) of about 2511 in air at ambient conditions. Through the use of finite element simulations, we show that the reported frequency of resonance is relevant. Also, the measurements were performed in an enclosed chamber with controlled levels of ethanol vapor. The adsorption of ethanol causes a shift in the... 

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.... 

A system of electrospun scaffold containing drug-loaded chitosan nanoparticles was introduced for using in spinal cord tissue engineering. In spinal cord injury treatment, the formation of glial scar after injury which contains proteoglycans and activate glial cells should be avoided. In this study, the release of Dexamethasone sodium phosphate (DEXP) as a steroid anti-inflammatory agent from electrospun nanofiber composite containing chitosan nanoparticles was investigated. DEXP is believed to act through its glucocorticoid receptors found in most neurons and glial cells. These receptors’ pathways are involved in the inhibition of astrocyte proliferation and microglial activation.... 

Amorphous SiBNC ceramics have been developed as new high temperature materials. They show a high resistance against crystallization, high mechanical properties, low density, and high oxidation stability. Three synthesis methods have been developed for synthesis of SiBNC ceramics namely, Reactive magnetron sputtering, Mechanical alloying plus sintering, and polymer-derived ceramics. In this research among polymeric methods one pot synthesis due to high ceramic yield and high mechanical properties have been chosen. Two major methods for nanofiber preparation are Meltspinning and Electrospinng. It is notable that all of researches for SiBNC Nanofiber preparation has been conducted on... 

Electrospinning process has been widely used to produce nanofibers from polymer blends. Poly(vinyl alcohol) (PVA) and chitosan (CS) have numerous biomedical applications such as wound healing and tissue engineering. Nanofibers of CS/PVA have been prepared by many works, however, a complete physicochemical and mechanical characterization as well as cell behavior has not been reported. In this study, Non-toxic, biodegradable, and biocompatible chitosan/poly(vinyl alcohol)(PVA)/nano silica nanofibers were prepared by electrospinning. The properties of the nanofibers at various blend ratios were investigated by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR)... 

Since cartilage has limited self-regeneration, in-situ forming hydrogels can act as an ideal scaffold for cartilage tissue engineering to fill the defect gap due to their ability to homogeneously encapsulate the desired cells, efficient mass transfer and minimally invasive characteristics. In this project, an injectable hydrogel with improved structure by adding silk fibroin (SF) nanofibers and better biochemical properties by employing the cartilage extracellular matrix (ECM) was fabricated. The in-situ forming hydrogel is consisted of different concentrations of ionic crosslinked alginate incorporated with different concentrations of SF nanofibers and 1% w/v enzymatically crosslinked... 

Nowadays, the use of processed conductive polymers for conducting matrix polymers, as well as improving other properties for planting in the body, is very common. In this project, the fabrication and identification of electrically conductive films and fibers from biocompatible poly lactic acid and conductive polyAniline polymer in the form of nano-fibers or nanoparticles was intended. These fibers and films have been made in form of a plate or tube then, have been used as biosensors. These polymeric prostheses should be sterilized before planting in human body. Gamma rays are the best sterilization methods and are used at low doses (25 kGy) to sterilize plastic medical supplies. On the other... 

Fabrication and characterization of different surface charged cellulose electrospun scaffolds including cellulose acetate, cellulose, carboxymethyl cellulose and quaternary ammonium cationic cellulose for biomedical applications have been reported in this research. We describe preparation of cellulosic nanofibers through the electrospinning following deacetylation cellulose acetate. Moreover, surface modification of electrospun cellulose nanofibers is carried out to obtain carboxymethyl cellulose and quaternized cellulose nanofibers, respectively. At last, the structural, morphological, mechanical, swelling, wettability and the cell culture properties of the scaffolds were analyzed and... 

In the framework of surface elasticity theory, the scattering of in-plane elastic waves by a multicoated nanofiber embedded in an elastic matrix is studied. Atoms near an interface experience a local environment different from it within the bulk. Going from macro to nano dimensions, surface to volume ratio increases significantly. Thus, on this scale it is important to consider the surface/interface properties as well as the bulk properties. In this dissertation, the surface/interface is modeled by a very thin layer in which the traction and displacement are discontinuous. Effects of surface/interface parameters on the dynamic stress concentration factor (DSCF) and scattering cross section... 

In tissue engineering and nerve cell treatments, biocompatible and conductive substrates are needed to stimulate nerve cells. In this project, we fabricated a composite of polyaniline and gelatin along with metal-organic frameworks and graphene quantum dots, which perform this repair process for us. For this purpose, we used polyaniline. Due to its conductivity, this polymer stimulates the nervous tissue and in this way, it can perform the repair work. By conducting UV-Vis and FTIR tests, it was observed that the synthesis of aniline polymer has been achieved successfully. SEM analysis showed that the polymer chains were well formed. The other part of the composite used is MOF (metal-organic...