Sharif Digital Repository

Poly (lactate-co-glycolate) is a typical biocompatible and biodegradable synthetic polymer. Addition of TiO2 nanoparticles improved compressive modulus of PLGA scaffolds and reduced fast degradation. Porous 3D scaffolds, which are synthesized using biocompatible and biodegradable materials, could provide suitable microenvironment and mechanical support for optimal cell growth and function. A novel method has been applied to fabricate PLGA/TiO2 scaffolds without using any organic solvent or porogen for nucleation compared to former ways, with aim of improving the biocompatibility, macroscale morphology and well inter-connected pores efficacy: Air-Liquid Foaming. Adjustment of the foaming... 

Hole-transporter-free perovskite solar cells with structure of TiO2/ZrO2/C triple-layer scaffold filled with perovskite are great alternative to the conventional ones due to the possibility of making full printable low-cost and stable devices. In the present work, the impacts of the structures of the quadruple layer scaffold in the form of TiO2/ZrO2/NiO/C and triple layer scaffold in the form of TiO2/ZrO2/C on their photovoltaic performance are studied. In addition, the effects of thickness and deposition method of each layer were investigated as well as the effect of compounding of the carbon counter electrode. All devices were constructed by a simple printable method. Electrochemical... 

This investigation presents synthesis and characterization of pure and monophasic hydroxyapatite (Ca10(PO4)6(OH)2; HA) Nanostructures prepared by coral and oyster shell powders heated at 800 oC for 8 h as precursor via precipitation method. The morphology of HA nanostructures was controlled in the presence of various surfactants such as SDS, CTAB and PVP. The HA Nanorods synthesized by SDS were applied to fabricate bone scaffolds. Particle sizes of the HA Nanoparticles were about 20-30 nm. Pours three-dimensional HA/Ge/CMC scaffolds cross-linked by citric and oxalic acids were synthesized. In order to increase the pore size of the scaffolds, NaCl with medium (180-250 µm) and large (420-500... 

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... 

Nervous system plays an intricate biological process of man body.Damage of nervous system has serious consequences and is hard to recover, as well as the other parts of the body may not work properly. Many strategies have been used to repair spinal cord injuries in which the main objective is to improve the regeneration of axons and functional recovery. The purpose of this research is introducing neural tissue engineering concepts (e.g. scaffolds, stimulation and etc.) and also design and fabrication suitable for neural tissue engineering. For this purpose the combination of biodegradable polymers (chitosan),conductive polymer (poly-aniline) and carbon nanosheets (graphene) was chosen as the... 

Tissue engineering has the potential to revolutionize our health care system. Conceptually, lost or malfunctioning tissues will be replaced by man-made biological substitutes to restore, maintain, or improve function. Tissue engineering has already shown great promise to contribute to treatments of a myriad of diseases including osteoarthritis, cancer, diabetes, skin burns, cardiovascular conditions and various traumatic injuries. Tissue engineering is a highly multidisciplinary discipline that demands integration of knowledge, tools and skills from biology, chemistry, engineering and medicine. Integrating nano- and microtechnologies into clinically sized implants represents a major... 

The accurate assessment of biomarkers likes proteins, hormones or other biomolecules that amount of them changes with state of disease or level of treatment and gives diagnostic information is a difficult duty. In these samples, pathogens exist in small quantity compared to other background molecules. Therefore, appropriate sampling process for concentrating and separating pathogens from the matrix should be developed in order to provide rapid and accurate pathogen detection test. In this thesis design and fabrication of microfluidic biosensors based on the modified nanofibrous membranes were investigated and explained. PES nanofibrous membrane with carboxyl functional groups for covalent... 

Polycaprolactone (PCL) scaffolds and its composites containing bioactive glass particles (45S5) and TiO2 nanostructures with pre-defined and controlled external and internal architecture were prepared via an indirect three-dimensional (3D) printing process. The scaffolds had an interconnected structure with macro- (400-500 μm) and micro- (~25 μm) pores. Bioactivity, mechanical behavior and kinetics of tissue growth in 3D scaffolds were studied. The size effect of biogactive glass particles (6 μm, 250 nm, <100 nm) and morphology of titania nanostructures (spherical, tube, leaf-like, and flower-like particles) were elaborated. The biogactive glass particles with different sizes were prepared... 

Cartilage is a connective tissue, whose most important role in the body is to create a surface with a low friction coefficient in order to allow bones to slide on each other without direct contact to transfer loads. Articular cartilage is always under a harsh biomechanical environment and lacks blood, lymphatic and nerve vessels. As a result, it limits the capacity of this tissue to improve and restore itself. According to experimental efforts, cartilage cannot be regenerated spontaneously without the support of healthy subchondral bone. In recent years, the implantation of tissue engineering scaffolds has been considered as an effective strategy for the treatment of osteochondral damage.... 

Nerve damage is one of the factors affecting the quality of life of patients. The nervous system does not have the ability to repair large injuries, and autologous transplantation, which is the standard treatment method for nerve injuries, is faced with a shortage of donors and a decrease in the function of the donor site. Tissue engineering hydrogels, due to their similarity to the natural tissue of the stomatal body, are a hope for the repair of nerve tissue. In this research, an injectable, minimally invasive and temperature-sensitive hydrogel based on chitosan-etaglycerophosphate-sodium hydrogen carbonate salt or trisodium phosphate salt containing aligned nanofibers made of gelatin and... 

Articular cartilage is devoid of blood vessels, lymphatics, and nerves which gives it a very limited intrinsic healing and repair capabilities. Being under constant harsh biomechanical environment, makes maintaining the health of articular cartilage a vital principle in having healthy joints. Tissue engineering as a method for regeneration of damaged tissue have attracted a lot of attention. Articular cartilage engineered scaffolds act as a macro scale drug delivery system which in addition to having a good mechanical properties similar to that of cartilage tissue, have to provide a highly porous environment for cell migration and proliferation. The aim of this study is to fabricate a drug... 

Skin, as the largest organ of the body and the first protector against external injuries, plays an important role in maintaining human health. Therefore, providing a method for complete treatment of skin lesions is very important. In the last century, tissue engineering approaches, with the introduction of skin scaffolds, have been instrumental in the process of skin tissue regeneration and treatment. The aim of the present study is to construct an optimal bilayer scaffold to mimic the two outer layer of the skin (epidermis and dermis). Besides, the effects of placenta extract on acceleration of wound healing was investigated by an in-vivo test. both layer of scaffold are porous hydrogels,... 

Since its successful synthesis as single layer during the past decades, Graphene and its derivatives have been extensively employed by many researchers in various science and engineering fields. The studies to characterize and define graphene behaviour are still in demand to answer the questions around these structures. The unique feathures of graphene such as high strength, good conductivity, large available surface, intoxicity and biocompatibility, has made it a suitable candidate to used in novel structures and materials. In this work, hybrid structures made from graphene and carbon nanotubes are investigated which can be utilized as scaffolds in tissue engineering.After an introduction... 

In recent years, additive manufacturing has been widely used in prototyping and production of industrial-commercial pieces. Additive manufacturing or three-dimensional (3D) printing is able to easily produce any piece for initial prototyping, no matter how complex it is. The fused deposition modeling (FDM) is a type of additive manufacturing process that produces the piece with the mechanism of feeding the PLA filament, then the molten polymer extrusion and depositing the fluid layer by layer with a high viscosity. Since the thickness of the layers is directly proportional to the diameter of the nozzle and the diameter of the used nozzles cannot be in the micron range (lower than 100... 

Skin as the largest organ of the body is constructed of three distinctive layers referred to as epidermis, dermis, and hypodermis. Epidermis is the outermost layer of the skin and acts as body’s first barrier against infectious agents and contains mostly sweat glands. Dermis is the mid-layer of the skin which makes up to 70% of the skin and plays a significant role in maintaining body’s metabolism and is home to a huge part of skin’s vascular network, nerve cells and hair follicles. Hypodermis on other hand, is the deepest layer of the skin and mainly acts as a bonding layer between upper skin layers and the soft tissue underneath. Although skin is proved to have a profound ability to... 

Skin tissue as the first protective barrier to the body is always exposed to the most injuries. The purpose of this project is to design an optimum skin scaffold capable of drug delivery for skin wounds healing. To this end, the skin scaffold has been considered as a combination of a hydrogel structure containing polymer microspheres carrying growth factor. Polyvinyl alcohol and sodium alginate polymers were utilized to make the hydrogel substrate. The hydrogel structure was optimized from the viewpoint of the percentage of gelation, water absorption, porosity, mechanical properties, biodegradability, biocompatibility and considering the volume percent of utilized polymers and the... 

Wound healing by engineered scaffolds is a new step in bio-technology and medical studies in recent years. The goal of the current study is to propose a novel structure for a tissue-engineered scaffold to be used in wound healing. Influenced from the multi-layered structure of natural human skin, the fabricated scaffold consists of two layers to maximize similarity with natural skin. This product is comprised of an electrospun layer made of polycaprolactone and polyvinyl alcohol and a hydrogel layer made of chitosan and gelatin. In order to form a porous medium in the hydrogel layer, freeze-gelation was used instead of freeze drying. The evaluation of fabricated scaffolds was performed by... 

Microfluidic systems create great development in diseases and drug delivery in various organs of the body. In this study, human pulmonary alveolar cell performance was evaluated from the perspective of the cell culture using a microfluidic system. For this purpose, numerical simulations of the microchip channels flow field are very important to select appropriate models. So in the first step, the flow field and particle deposition were simulated. Then an optimal model was selected based on key parameters such as cell feeding, shear stress exerted on the cell, particles distribution and also the limitations and possibilities for constructing. The numerical results show that the shear stress,... 

Cardiovascular diseases are the leading cause of death all over the world, even more common than cancers. The first reason of mortality in Iran according to statistics is the occlusion of coronary arteries. Unfortunately almost one third of patients doesn’t have enough blood vessels to be used in the bypass surgery and need artificial vessels. These artificial blood vessels with small diameters (less than 6 mm) will fail quickly. As a result there is an increasing demand for tissue engineered blood vessels which are capable of enduring high blood pressures. An artificial blood vessel should mimic both structure and mechanical properties of the real one. Blood vessels have layered structures,...