Sharif Digital Repository

Thermosensitive Chitosan hydrogels which can be injected into defects with minimally invasive approach were prepared. Also starch micro/nano particles were synthesized via water-in-oil (W/O) miniemulsion technique. The starch particles were incorporated into the chitosan hydrogel to prepare injectable thermosensitive hydrogel composites. Tube inverting method, compression tests, swelling studies, XRD, SEM, OM, DLS, UV–vis spectroscopy were used for investigations. Results revealed that increasing crosslinker and surfactant contents and stirring rate leads to particle size reduction. Particle size was modeled using design of experiments (DOE) via the response surface method (RSM). Due to... 

Biocompatible porous polymeric scaffolds provide a suitable environment for proliferation of stem cells in human body. In this research work, porous gelatin–poly(ethylene glycol), PEG, based scaffolds were prepared using combination of freeze-gelation and freeze-extraction methods. Effects of various parameters such as freezing temperature, cross-linking agent, concentrations of gelatin and PEG and their blending ratio on physical and mechanical properties, swelling ratio, porosity, pore size, and degradation rate of scaffolds were investigated. Also, proliferation of fibroblast skin cells on the scaffolds was examined by MTS assay to assess the suitability of the scaffolds in wound healing... 

Porous NiTi shape memory alloy (SMA) was fabricated by sintering of compressed constituent elements pre-mixed with NaCl or urea spacer holders. Effect of spacer to metal volume-ratio (r S) on shape, size, distribution and openness of the voids was probed by optical metallography, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) was used to determine the SMA transformation temperatures. Controllable void geometry helping osteoblast proliferation and bone cell growth was gained by addition of the spacers. At r S = 0.7, percentage of the open pores reached 52% while at r S = 1.43, interconnected pores with 200 to 500 μm diameter were... 

Natural silk fibroin (SF) polymer has biomedical and mechanical properties as a biomaterial for bone tissue engineering scaffolds. Freeze-dried porous nanocomposite scaffolds were prepared from silk fibroin and titanium dioxide (TiO2) nanoparticles as a bioactive reinforcing agent by a phase separation method. In order to fabricate SF/TiO2 scaffolds, 5, 10, 15 and 20 wt% of the TiO2 were added to the SF. The phase structure, functional groups and morphology of the scaffolds were evaluated using X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy techniques, respectively. Porosity of the scaffolds was measured by Archimedes' Principle. In addition,... 

Due to the advent and maturity of the additive manufacturing technology, it is possible now to construct complex microstructures with unprecedented accuracy. In addition, to the influence of network unit cell types and porosities in recent years, researchers have studied the number of scaffold layers fabricated by additive manufacturing on mechanical properties. The objective of this paper is to assess the numerical and analytical simulations of the multilayer scaffolds. For this purpose, 54 different regular scaffolds with a unit cell composed of multilayer scaffolds were simulated under compressive loading and compared with the analytical relationships based on the Euler–Bernoulli and... 

It is known that Fluoride ions strongly affect bone mineralization and formation. In the present study, the engineered bone tissue scaffolds are fabricated using silk fibroin (SF) and flouridated TiO2 nanoparticles. TiO2 nanoparticles are modified by fluoride ions, and different levels (0, 5, 10, 15 and 20 wt%) of the fluoridated TiO2 nanoparticles (TiO2-F) were subsequently added to the SF matrix through phase separation method to prepare silk fibroin/flouridated TiO2 nanocomposite scaffolds (SF/TiO2-F). Phase structure, functional groups, morphology and mechanical properties of the obtained scaffolds were evaluated by X-ray diffraction method (XRD), Fourier transform infrared spectroscopy... 

Natural compounds containing polysaccharide ingredients have been employed as candidates for treatment of skin tissue. Herein, for the first time, electrospinning setup was proposed to fabricate an efficient composite nanofibrous structure of Beta vulgaris (obtained from Beet [Chenopodiaceae or Amaranthaceae]) belonged to polysaccharides and an elastic polymer named nylon 66 for skin tissue engineering. Both prepared scaffolds including noncomposite and composite types were studied by Scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, mechanical assay, and contact angle. Scanning electron microscope examinations have approved the uniform and homogeneous... 

According to the latest report from the World Health Organization, an estimated 265,000 deaths still occur every year as a direct result of burn injuries. A widespread range of these deaths induced by burn wound happens in low- and middle-income countries, where survivors face a lifetime of morbidity. Most of the deaths occur due to infections when a high percentage of the external regions of the body area is affected. Microbial nutrient availability, skin barrier disruption, and vascular supply destruction in burn injuries as well as systemic immunosuppression are important parameters that cause burns to be susceptible to infections. Topical antimicrobials and dressings are generally... 

3D hydrogel environment with both unique properties of nanofibrous structure and electrical character can provide a promising scaffold for skeletal muscle tissue engineering approaches. Herein, the poly acrylic acid (PAA)-based hydrogel was engineered to conductive one by aniline polymerization in the form of nanofibers. The poly aniline (PANi) nanofibers were made by the optimized chemical reactions between the surface carboxylate groups of based hydrogel and protonated aniline monomers. We found that the strong bonding which was created between PANi and camphor sulphonic acid (CSA) as a doping agent supporting the stable electrical property of composite hydrogel after incubation in cell... 

Recently, nanodiamonds have attracted interest in biomedical applications such as drug delivery, targeted cancer therapies, fabrication of tissue scaffolds, and biosensors. We incorporated diamond nanoparticles in alginate-bioactive glass films by electrophoretic process to prepare functional coatings for biomedical implants. Turbidity examination by time-resolved laser transmittance measurement revealed that a stable multi-component aqueous suspension of alginate, bioactive glass and diamond particles could be obtained at concentrations of 0.6, 1.3, and 0.65 g/l, respectively. Uniform films with ~ 5 μm thickness were deposited on 316 stainless steel foils by employing constant field... 

Electrospray ionization is a wide spread technique for producing polymeric microcarriers (MCs) by applying electrostatic force and ionic cross-linker, simultaneously. In this study, fabrication process of gelatin-chitosan MCs and its optimization using the Response Surface Methodology (RSM) is reported. Gelatin/chitosan (G/C) blend ratio, applied voltage and feeding flow rate, their individual and interaction effects on the diameter and mechanical strength of the MCs were investigated. The obtained models for diameter and mechanical strength of MCs have a quadratic relationship with G/C blend ratio, applied voltage and feeding flow rate. Using the desirability curve, optimized G/C blend... 

Three-dimensional porous scaffolds are essential in tissue engineering applications. One of the most conventional methods to form porosity in scaffolds is freeze-drying, which is not energy efficient and cost effective. Therefore in this work, it was experimentally investigated whether gelatin, with its unique mechanical properties and cell binding applications, could be used as a comprising polymer of scaffolds with porous structure made by the freeze-gelation method. Chitosan, gelatin and chitosan/gelatin scaffolds were fabricated by the freeze-gelation method and their behaviors, determined by analysis of scanning electron microscopy images, Fourier transform infrared spectroscopy,... 

The solar to electric power conversion efficiency (PCE) of perovskite solar cells (PSCs) has recently reached 22.7%, exceeding that of competing thin film photovoltaics and the market leader polycrystalline silicon. Further augmentation of the PCE toward the Shockley-Queisser limit of 33.5% warrants suppression of radiationless carrier recombination by judicious engineering of the interface between the light harvesting perovskite and the charge carrier extraction layers. Here, we introduce a mesoscopic oxide double layer as electron selective contact consisting of a scaffold of TiO2 nanoparticles covered by a thin film of SnO2, either in amorphous (a-SnO2), crystalline (c-SnO2), or... 

For a successful repair and reconstruction of bladder tissue, fabrication of scaffolds with proper biochemical and biomechanical characteristics is necessary. Decellularized bladder tissue has been proposed in previous studies as a gold standard material for scaffold fabrication. However, weak mechanical properties of such a load-bearing tissue has remained a challenge. Incorporation of both biological and synthetic materials has been known as an effective strategy for improving mechanical and biological properties of the scaffolds. In the present work, a simple process was developed to fabricate hybrid hydrogel scaffolds with a biomimetic architecture from the natural urinary bladder... 

Biocompatible and biodegradable three-dimensional scaffolds are commonly porous which serve to provide suitable microenvironments for mechanical supporting and optimal cell growth. Silk fibroin (SF) is a natural and biomedical polymer with appropriate and improvable mechanical properties. Making a composite with a bioceramicas reinforcement is a general strategy to prepare a scaffold for hard tissue engineering applications. In the present study, SF was separately combined with titanium dioxide (TiO2) and fluoridated titanium dioxide nanoparticles (TiO2-F) as bioceramic reinforcements for bone tissue engineering purposes. At the first step, SF was extracted from Bombyx mori cocoons. Then,... 

The performance of cellular solids in biomedical applications relies strongly on a detailed understanding of the effects of pore topology on mechanical properties. This study aims at characterizing the failure mechanism of scaffolds based on nodal connectivity (number of struts that meet in joints) and geometry of the pores. Plastic models of scaffolds having the same relative density but different cubic and trigonal unit cells were designed and then fabricated via three dimensional (3-D) printing. Unit cells were repeated in different arrangements in 3-D space. An in-situ imaging technique was utilized to study the progressive deformation of the scaffold models. Different nodal... 

Hydroxyapatite (HA) is the most substantial mineral constituent of a bone which has been extensively used in medicine as implantable materials, owing to its good biocompatibility, bioactivity high osteoconductive, and/or osteoinductive properties. Nevertheless, its mechanical property is not utmost appropriate for a bone substitution. Therefore, a composite consist of HA and a biodegradable polymer is usually prepared to generate an apt bone scaffold. In the present work polycaprolactone (PCL), a newly remarkable biocompatible and biodegradable polymer, was employed as a matrix and hydroxyapatite nanoparticles were used as a reinforcement element of the composite. HA/PCL nanocomposites were... 

Interface engineering of solar cell device is a prominent strategy to improve the device performance. Herein, we synthesize reduced-graphene scaffold (rGS) by using a new and simple chemical approach. In this regard, we synthesize a hollow structure of graphene and then fabricate a three-dimensional scaffold of graphene with a superior surface area using electrophoretic process. We employ this scaffold as an interface layer between the electron transfer and absorber layers in perovskite solar cell. The characterization tests and photovoltaic results show that rGS improves the carrier transportation, yielding a 27% improvement in device performance as compared to conventional device. Finally,... 

The in vitro endothelial response of human umbilical vein endothelial cells was investigated on a poly (caprolactone)-based polyurethane surface vs an in situ TiO2-polyurethane nanocomposite surface, which has been produced as scaffolds for artificial vascular graft. The in situ synthesis of TiO2 nanoparticles in polyurethane provided surface properties that facilitated cellular adhesion, cell sensing, cell probing and especially cell migration. Cells on the nanocomposite surface have elongated morphology and were able to produce more extracellular matrix. All of these advantages led to an increase in the rate of endothelialization of the nanocomposite scaffold surface vs pure polyurethane.... 

This work has focused on in-situ crosslinking of gelatin (G) to produce electrospun scaffold with improved fiber morphology retention and mechanical properties. As per this approach, we prepared G nanofibers through mixing G, 1-ethyl-3-(3 dimethylaminopropyl) carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) in the new solvent system. Response surface methodology (RSM) was employed to study the influence of solution parameters on fiber diameter. The morphological structure was examined, and the appropriate level of setting to obtain smooth fibers with a favorable diameter was reported. Results revealed using EDC/NHS for in-situ crosslinking improves the mechanical properties...