Sharif Digital Repository

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,... 

Today, hydrogels have various biomedical applications as three-dimensional networks with the ability to absorb and retain water and biological fluids. This study aimed to prepare nanocomposite hydrogels from polyvinyl pyrrolidone, polyethylene glycol, and barium titanate nanoparticles. Gamma radiation at irradiation doses of 25 and 35 kGy was used as the hydrogel's crosslinking agent. The effects of gamma irradiation dose, percentage of polyethylene glycol, and barium titanate composition on the swelling ratio and gel content were investigated. It was observed that the amount of gel content with the addition of polyethylene glycol and barium titanate nanoparticles reduces the gel content and... 

Today, supercapacitors are an inseparable component of electronic devices such as hybrid cars, telecommunication equipment, and personal electronic devices, and this device is also used to store clean energy. In this research, polyacrylic acid hydrogel was first synthesized to be used as a supercapacitor electrode and polyaniline was used as an electrically conductive polymer in its structure to improve the electrical properties of this hydrogel. To achieve this structure, the previously synthesized polyacrylic acid hydrogel was immersed in a solution of aniline monomer and other components necessary for the aniline polymerization reaction, and after the soaking process was completed, 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... 

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... 

Growth factors play an important role in tissue repair and regeneration including articular cartilage tissue. Direct injection of growth factor is a common practice in clinics. However, it has been shown that this method is not very effective and, in some cases, induces some side effects. Moreover, incorporation of this valuable signals in systems where they are quickly released and washed out is not effective as well. Thereby the aim of this study was to design and fabricate an efficient system to effectively deliver growth factors for cartilage tissue engineering. The designed system is an injectable, in situ forming hydrogel, based on hyaluronic acid (HA) as a biocompatible and attractive... 

Hydrogels are of growing interest for fabrication of wearable strain sensors due to their intrinsic ionic conductivity, flexibility, and biocompatibility. Herein, to improve the mechanical properties of hydrogels, conventional covalent crosslinking is replaced with novel physical cross-linking. First, the microstructure and properties of pure hydrogel is optimized. Then, Cellulose nanocrystal (CNC) is added to the optimized gel to reinforce it. Finally, through a sequential strategy, aniline monomers are diffused into the gel network and are in-situ polymerized accordingly, providing high conductivity of 21.7 S/m. The resulting hydrogel has the stretchability of 2500% and the toughness of... 

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... 

In this research, we developed a drug release system of two biocompatible and biodegradable polymers and biocompatible ceramic nanoparticles. Hydrogels of sodium alginate (SA) were crosslinked using calcium chloride. The SA hydrogels were blended with polyvinyl pyrrolidone (PVP) and mixed with hydroxyapatite nanoparticles (HAP) to make hydrogel nanocomposites in the form of microbeads as drug carriers. Ciprofloxacin was selected as a model antibiotic drug for treatment of bone infection. It was found that SA and PVP form hydrogen bonds and are miscible at whole range of concentrations. Indeed, the SA/PVP blends may be considered as interpenetrating polymer networks (IPNs). HAP nanoparticles... 

In this research, porous polyvinyl¬ alcohol (PVA)/Montmorillonite nanoclay and polyvinyl alcohol/polyvinyl pyrrolidone (PVP)/Montmorillonite nanoclay nanocomposite sponges (foams) were fabricated by freeze-drying method. The foams were crosslinked using gamma irradiation. The pore size and interconnectivity of nanocomposites characterized by scanning electron microscopy (SEM), showed bimodal pore size distribution resulting from preparation method.
SEM micrographs displayed that addition of PVP ( wt% of total solid polymer) to the PVA sponges increased the pore size and interconnectivity, due to the optimal number of hydrogen bonds between functional groups of polymeric matrices.... 

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... 

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... 

Articular cartilage resides in a complex and dynamic mechanical and biophysical environment in vivo. Chondrocyte physiology and biosynthetic activity is influenced by these signals, allowing them to modulate the structural organization and function of tissue at all stages, including development, growth and repair. . In articular cartilage, during physical activity and mechanical loading, electric signal have been observed in form of stress-generated electric potential following the movement of the positive mobile ions (in interstitial fluid) away from the fixed negative charges.Despite increasing evidence that mechanical and electrical stimuli have positive effects on chondrogenesis, to... 

Platelet Rich Plasma (PRP) is a blood-derived product containing concentrate of platelets, which are a rich source of autologous growth factors. PRP injection has been used clinically as a therapeutic method for cartilage repair. However, clinical efficiency of this method is unpredictable, maybe as a result of burst release of growth factors then fail cell-stimulating potential as most biomolecules are cleaned before they can exert a therapeutic effect. The aim of this project was to prepare a suitable scaffold for PRP delivery to regenerate cartilage injuries. In order to resemble polysaccharide-protein nature of the cartilaginous extracellular matrix, in this study, we developed an... 

Corneal diseases are one of the most common causes of blindness worldwide. The most common way to treat these diseases is to replace the damaged cornea with the donor cornea by corneal transplant. But limitations such as donor tissue deficiency, the risk of disease transmission and transplant rejection have made treatment of these diseases very difficult. A cornea made by tissue engineering can be used as a suitable alternative because of the limitations mentioned for corneal transplantation with donated tissue. At the same time, similarity of the scaffold to normal corneal tissue, both in terms of matrial and structural properties, is essential for proper repair of this scaffold by cells... 

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... 

Pulp necrosis in immature teeth disrupts root development and predisposes roots to fracture as a consequence of their thin walls and open apices. Regenerative endodontics is a developing treatment modality whereby necrotic pulps are replaced with newly formed healthy pulp-like tissue. Many clinical studies have demonstrated the potential of this strategy to stimulate root maturation and apical root-end closure. However, clinical outcomes are patient-dependent and unpredictable. The development of predictable clinical protocols is achieved through the interplay of the three classical elements of tissue engineering, namely, stem cells, signaling molecules, and scaffolds. Scaffolds provide... 

Periodontitis is a common inflammatory disease that affects the periodontium.Periodontium includes two hard tissues of cementum and alveolar bone and also soft tissue of periodontal ligament. The appropriate function is based on the consistency and accurate interaction of them. The complex structure, the low potential of the body for spontaneous healing, and technical problems such as bacteria accumulation, limited access, and small operating field cause no complete treatment can be achieved until now.In this project, at first collagen type I was extracted from Bovine Achilles tendon. Then, polymer modification was done to 39.95 µg/mg (Tyramine/ Collagen). An In situ gel based on modified... 

This article investigates the production of a novel nerve regeneration scaffold by using biodegradable and biocompatible components. In this research, we have provided different methods like electrospinning and PE hydrogels to fabricate it. Electrospun fibers are made of PLLA and CS/Gel combinations. ZnO nanoparticles were used as the piezoelectric agent. Piezoelectricity plays an important part in the strcture of neurons giving them the ability to transfer electrical messages throughout the body. NPs were completely dispersed in the PLLA solution. ZnO particles could increase produced voltages as the concentration increases. PLLA is biodegradable and provide good mechanical properties.... 

Myocardial infarction (MI) is one of the diseases caused by the temporary or permanent cramp of major coronary arteries. Due to this blockage, blood flow to the heart's myocardial tissue is greatly reduced and finally the person suffered from a Heart stroke (HS). Heart tissue engineering is a promising approach, based on the combination of cells and suitable biomaterials to develop and create heart-like biological substitutes. Since high cardiac cell density, providing metabolic needs like oxygen and nutrients was a challenge. So creation of blood vessel networks within this type of designed tissue has been considered very much.The purpose of this project is to construct scaffolds with...