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Experimental investigation and finite element modelling of PMMA/carbon nanotube nanobiocomposites for bone cement applications
, Article Soft Matter ; Volume 18, Issue 36 , 2022 , Pages 6800-6811 ; 1744683X (ISSN) ; Khakbiz, M ; Chagami, M ; Bagheri, R ; Chashmi, F. S ; Akbari, B ; Shakibania, S ; Lee, K. B ; Sharif University of Technology
Royal Society of Chemistry
2022
Abstract
Multi-walled carbon nanotubes (MWCNTs) are one of the preferred candidates for reinforcing polymeric nanobiocomposites, such as acrylic bone type of cement. In this study, at first, bulk samples of the reinforced polymethylmethacrylate (PMMA) matrix were prepared with 0.1, 0.25, and 0.5 wt per wt% of MWCNTs by the casting method. Tensile and three-point bending tests were performed to determine the essential mechanical properties of bone cement, such as tensile and bending strengths. The tensile fracture surfaces were investigated by scanning electron microscopy (SEM). The commercial software (Abaqus) was used to conduct finite element analysis (FEA) by constructing a representative volume...
Fabrication and characterization of scaffolds containing different amounts of allantoin for skin tissue engineering
, Article Scientific Reports ; Volume 11, Issue 1 , 2021 ; 20452322 (ISSN) ; Shamloo, A ; Bahadoran, M ; Moravvej, H ; Sharif University of Technology
Nature Research
2021
Abstract
Using the skin tissue engineering approach is a way to help the body to recover its lost skin in cases that the spontaneous healing process is either impossible or inadequate, such as severe wounds or burns. In the present study, chitosan/gelatin-based scaffolds containing 0.25, 0.5, 0.75, and 1% allantoin were created to improve the wounds’ healing process. EDC and NHS were used to cross-link the samples, which were further freeze-dried. Different in-vitro methods were utilized to characterize the specimens, including SEM imaging, PBS absorption and degradation tests, mechanical experiments, allantoin release profile assessment, antibacterial assay, and cell viability and adhesion tests....
Porous shape memory dental implant by reactive sintering of TiH2–Ni-Urea mixture
, Article Materials Science and Engineering C ; Volume 107 , 2020 ; Sadrnezhaad, S .K ; Hosseini, S. A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
We produced bifurcated bone-like shape memory implant (BL-SMI) with desirable tooth-root fixation capability by compact-sintering of TiH2–Ni-urea mixture. The primary constituents of the porous product were Ni and Ti. We could adjust the pores' shape, size, and interconnectivity for favorite bone ingrowth by using urea as a space holder. Without urea, we obtained an average porosity of 0.30, and a mean void size of 100 μm. With 70 vol % urea, we got 62% interconnected pores of 400 μm average size. Aging allowed us to tune the austenite-martensite transformation temperatures towards the needed body tissue arouse. Differential scanning calorimetry measured the transformation temperatures....
The geometrical characteristics of nickel-based metal organic framework on its entrapment capability
, Article Journal of Chromatography A ; Volume 1610 , 2020 ; Abbasi, A ; Bagheri, H ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Here, a three dimensional nickel–based metal organic framework (MOF) was synthesized via solvothermal and room temperature protocols. In order to study the effects of the synthesis conditions on the physical properties such as pore sizes and shapes of the prepared MOFs, their extraction capabilities were examined. Both MOFs were characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller and thermogravimetric analyses. Brilliant properties such as porous structure, high surface area and considerable thermal stability make them reasonable candidates to be employed as efficient extractive phases. The efficiency of the...
Production of high quality ammonium uranyl carbonate from “uranyl nitrate + carbonate” precursor solution
, Article Progress in Nuclear Energy ; Volume 122 , 2020 ; Outokesh, M ; Zare, M. H ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
The purpose of this study is to investigate production of high quality ammonium uranyl carbonate (AUC) from “uranyl nitrate + ammonium bicarbonate”, or “uranyl nitrate + sodium carbonate” precursor solutions, by controlled injection of ammonium carbonate solution which could be applicable in material testing reactor (MTR) fuel production plant for recycling of rejected uranium oxide powder. The experimental observations revealed: at pHs higher than 6, precipitation proceeds with formation of no intermediate, thus ensuing a better morphology and size distribution of the AUC products. The results of scanning electron microscopy, X-ray diffraction, particle size analysis, and uranium content...
Fabrication and characterization of core-shell electrospun fibrous mats containing medicinal herbs for wound healing and skin tissue engineering
, Article Marine Drugs ; Volume 17, Issue 1 , 2019 ; 16603397 (ISSN) ; Esmaeili, A ; Eslahi, N ; Shokrgozar, M. A ; Simchi, A ; Sharif University of Technology
MDPI AG
2019
Abstract
Nanofibrous structures mimicking the native extracellular matrix have attracted considerable attention for biomedical applications. The present study aims to design and produce drug-eluting core-shell fibrous scaffolds for wound healing and skin tissue engineering. Aloe vera extracts were encapsulated inside polymer fibers containing chitosan, polycaprolactone, and keratin using the co-axial electrospinning technique. Electron microscopic studies show that continuous and uniform fibers with an average diameter of 209 ± 47 nm were successfully fabricated. The fibers have a core-shell structure with a shell thickness of about 90 nm, as confirmed by transmission electron microscopy. By...
Bilayered heparinized vascular graft fabricated by combining electrospinning and freeze drying methods
, Article Materials Science and Engineering C ; Volume 94 , 2019 , Pages 1067-1076 ; 09284931 (ISSN) ; Shamloo, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Small diameter vascular grafts (<6 mm) are highly demanded for patients suffering from severe occluded arteries to be used as a bypass or substituted conduit. Fabricating a graft with appropriate structural, mechanical and cell growth properties which has simultaneously anti-thrombogenic trait is a challenge nowadays. Here, we proposed a bilayer heparinized vascular graft that can mimic the structural and mechanical characteristics close to those of the native coronary artery by combining electrospinning and freeze drying methods. In this study, the inner layer was made by co-electrospinning of synthetic polymer, poly-caprolactone (PCL) and the natural polymer, gelatin (Gel). Also, heparin...
Bilayered heparinized vascular graft fabricated by combining electrospinning and freeze drying methods
, Article Materials Science and Engineering C ; Volume 94 , 2019 , Pages 1067-1076 ; 09284931 (ISSN) ; Shamloo, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Small diameter vascular grafts (<6 mm) are highly demanded for patients suffering from severe occluded arteries to be used as a bypass or substituted conduit. Fabricating a graft with appropriate structural, mechanical and cell growth properties which has simultaneously anti-thrombogenic trait is a challenge nowadays. Here, we proposed a bilayer heparinized vascular graft that can mimic the structural and mechanical characteristics close to those of the native coronary artery by combining electrospinning and freeze drying methods. In this study, the inner layer was made by co-electrospinning of synthetic polymer, poly-caprolactone (PCL) and the natural polymer, gelatin (Gel). Also, heparin...
Effect of stress direction on the cyclic resistance of sand
, Article Proceedings of the Institution of Civil Engineers: Geotechnical Engineering ; Volume 171, Issue 2 , April , 2018 , Pages 109-120 ; 13532618 (ISSN) ; Zamanian, M ; Sharif University of Technology
ICE Publishing
2018
Abstract
In total, 55 undrained cyclic torsional shear tests were conducted at a constant mean confining stress, σ0m, constant intermediate principal stress ratios, b = (σ2 − σ3)/(σ1 − σ3), and principal stress directions, α. The cyclic resistance of loose, isotropically consolidated specimens exhibited a dip in strength, with the lowest values for α being 45°, an angle at which α was oriented such that the potential shear band directions dovetailed with the plane having the weakest strength (i.e. horizontal plane). For a given α, the cyclic resistance decreased to the lowest values for b = 0·5, at which the value of the principal stresses was different in the three major directions. For dense...
Development of a stress-mode sensitive viscoelastic constitutive relationship for asphalt concrete: experimental and numerical modeling
, Article Mechanics of Time-Dependent Materials ; Volume 21, Issue 3 , 2017 , Pages 383-417 ; 13852000 (ISSN) ; Tabatabaee, N ; Jahanbakhsh, H ; Jahangiri, B ; Sharif University of Technology
Springer Netherlands
2017
Abstract
Asphalt binder is responsible for the thermo-viscoelastic mechanical behavior of asphalt concrete. Upon application of pure compressive stress to an asphalt concrete specimen, the stress is transferred by mechanisms such as aggregate interlock and the adhesion/cohesion properties of asphalt mastic. In the pure tensile stress mode, aggregate interlock plays a limited role in stress transfer, and the mastic phase plays the dominant role through its adhesive/cohesive and viscoelastic properties. Under actual combined loading patterns, any coordinate direction may experience different stress modes; therefore, the mechanical behavior is not the same in the different directions and the asphalt...
Preparation of biodegradable gelatin/PVA porous scaffolds for skin regeneration
, Article Artificial Cells, Nanomedicine and Biotechnology ; Volume 45, Issue 5 , 2017 , Pages 928-935 ; 21691401 (ISSN) ; Dadbin, S ; Frounchi, M ; Rajabi, S ; Sharif University of Technology
Taylor and Francis Ltd
2017
Abstract
Porous scaffolds composed of gelatin/poly (vinyl alcohol), (Gel/PVA), were prepared using combination of freeze gelation and freeze drying methods. The effect of polymer concentration, gelatin/PVA ratio, and glutaraldehyde/gelatin ratio (GA/Gel) was investigated on morphology of pores, swelling ratio, biodegradation, and skin cell culture. At optimum preparation conditions the scaffolds had uniform pore size distributions showing high swelling ratio of 23.6. The scaffolds were of biodegradable nature and almost degraded in 28 days. Human dermal fibroblast cells (HDF) were cultured on the scaffolds and MTS assay was conducted to evaluate the influence of PVA on growth and proliferation of the...
Temporary skin grafts based on hybrid graphene oxide-natural biopolymer nanofibers as effective wound healing substitutes: pre-clinical and pathological studies in animal models
, Article Journal of Materials Science: Materials in Medicine ; Volume 28, Issue 5 , 2017 , 73 ; 09574530 (ISSN) ; Eslahi, N ; Mehdipour, A ; Mohammadi, M ; Akbari, M ; Samadikuchaksaraei, A ; Simchi, A ; Sharif University of Technology
Springer New York LLC
2017
Abstract
Abstract: In recent years, temporary skin grafts (TSG) based on natural biopolymers modified with carbon nanostructures have received considerable attention for wound healing. Developments are required to improve physico-mechanical properties of these materials to match to natural skins. Additionally, in-deep pre-clinical examinations are necessary to ensure biological performance and toxicity effect in vivo. In the present work, we show superior acute-wound healing effect of graphene oxide nanosheets embedded in ultrafine biopolymer fibers (60 nm) on adult male rats. Nano-fibrous chitosan-based skin grafts crosslinked by Genepin with physico-mechanical properties close to natural skins were...
A Study on Flow Behavior of AA5086 Over a Wide Range of Temperatures
, Article Journal of Materials Engineering and Performance ; Volume 25, Issue 3 , 2016 , Pages 1076-1084 ; 10599495 (ISSN) ; Jamshidi Aval, H ; Serajzadeh, S ; Sharif University of Technology
Springer New York LLC
2016
Abstract
Flow stress behavior of AA5086 was determined using tensile testing at different temperatures from room temperature to 500 °C and strain rates varying between 0.002 and 1 s−1. The strain rate sensitivity parameter and occurrence of dynamic strain aging were then investigated in which an Arrhenius-type model was employed to study the serrated flow. Additionally, hot deformation behavior at temperatures higher than 320 °C was evaluated utilizing hyperbolic-sine constitutive equation. Finally, a feed forward artificial neural network model with back propagation learning algorithm was proposed to predict flow stress for all deformation conditions. The results demonstrated that the strain rate...
Joint mapping of mobility and trap density in colloidal quantum dot solids
, Article ACS Nano ; Volume 7, Issue 7 , 2013 , Pages 5757-5762 ; 19360851 (ISSN) ; Sutherland, B. R ; Ren, Y ; Ning, Z ; Simchi, A ; Thon, S. M ; Hoogland, S ; Sargent, E. H ; Sharif University of Technology
2013
Abstract
Field-effect transistors have been widely used to study electronic transport and doping in colloidal quantum dot solids to great effect. However, the full power of these devices to elucidate the electronic structure of materials has yet to be harnessed. Here, we deploy nanodielectric field-effect transistors to map the energy landscape within the band gap of a colloidal quantum dot solid. We exploit the self-limiting nature of the potentiostatic anodization growth mode to produce the thinnest usable gate dielectric, subject to our voltage breakdown requirements defined by the Fermi sweep range of interest. Lead sulfide colloidal quantum dots are applied as the active region and are treated...
Do the soft tissues located outside tibiofemoral joint have a role in bearing the compressive loads of the joint? An in-vitro study on sheep stifle joints
, Article Gazzetta Medica Italiana Archivio per le Scienze Mediche ; Volume 172, Issue 7-8 , 2013 , Pages 595-601 ; 03933660 (ISSN) ; Rostami, M ; Parnianpour, M ; Jabalameli, M ; Sharif University of Technology
2013
Abstract
Aim. The compressive loads on the tibiofemoral joint are normally assumed to be borne solely via contact and pressing of the cartilage surfaces of tibia and femur. However, recent findings suggest that non-contact load-bearing mechanisms are active in the joint as well. In this context, a non-contact load-bearing mechanism involving soft tissue connections outside the tibiofemoral joint has been hypothesized as well. This paper addresses the validity of this hypothesis and the possible involvement of several soft tissue connections outside the joint. Methods. Sheep stifle (knee) joints were studied in vitro. The specimens were loaded in fixed displacement. Various soft tissues outside the...
Preparation and characterization of multi-walled carbon nanotube/hydroxyapatite nanocomposite film dip coated on Ti-6Al-4V by sol-gel method for biomedical applications: An in vitro study
, Article Materials Science and Engineering C ; Volume 33, Issue 4 , 2013 , Pages 2002-2010 ; 09284931 (ISSN) ; Hooshmand, T ; Mohammadi, M ; Najafi, F ; Sharif University of Technology
2013
Abstract
In the present research, the introduction of multi-walled carbon nanotubes (MWCNTs) into the hydroxyapatite (HA) matrix and dip coating of nanocomposite on titanium alloy (Ti-6Al-4V) plate was conducted in order to improve the performance of the HA-coated implant via the sol-gel method. The structural characterization and electron microscopy results confirmed well crystallized HA-MWCNT coating and homogenous dispersion of carbon nanotubes in the ceramic matrix at temperatures as low as 500 C. The evaluation of the mechanical properties of HA and HA/MWCNT composite coatings with different weight percentages of MWCNTs showed that the addition of low concentrations of MWCNTs (0.5 and 1 wt.%)...
Manipulating failure mechanism of rapid prototyped scaffolds by changing nodal connectivity and geometry of the pores
, Article Journal of Biomechanics ; Volume 45, Issue 16 , 2012 , Pages 2866-2875 ; 00219290 (ISSN) ; Bagheri, R ; Zehtab Yazdi, A ; Sharif University of Technology
2012
Abstract
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...
Surface modification for titanium implants by hydroxyapatite nanocomposite
, Article Caspian Journal of Internal Medicine ; Volume 3, Issue 3 , 2012 , Pages 460-465 ; 20086164 (ISSN) ; Solati Hashjin, M ; Nik, S. N ; Nemati, A ; Sharif University of Technology
2012
Abstract
Background: Titanium (Ti) implants are commonly coated with hydroxyapatite (HA). However, HA has some disadvantages such as brittleness, low tensile strength and fracture toughness. It is desirable to combine the excellent mechanical properties of ZrO 2 and the chemical inertness of Al 2O 3 with respect to the purpose of this project which was coating Ti implants with HA-ZrO 2-Al 2O 3 to modify the surface of these implants by adding ZrO 2 and Al 2O 3 to HA. The purpose of this study was to evaluate the efficacy of hydroxyapatite coating nonocomposite. Methods: From September 2009 to January2011, functionally graded HA-Al 2O 3-ZrO 2 and HA coatings were applied on Ti samples. HA-Al 2O 3-ZrO...
Design and Synthesis of Novel Polyglycerol Hybrid Nanomaterials for Potential Applications in Drug Delivery Systems
, Article Macromolecular Bioscience ; Volume 11, Issue 3 , NOV , 2011 , Pages 383-390 ; 16165187 (ISSN) ; Adeli, M ; Vossoughi, M ; Shokrgozar, M. A ; Sharif University of Technology
2011
Abstract
The synthesis of a new drug delivery system based on hybrid nanomaterials containing a β-CD core and hyperbranched PG is described. Conjugating PG branches onto β-CD not only increases its water solubility but also affects its host/guest properties deeply. It can form molecular inclusion complexes with small hydrophobic guest molecules such as ferrocene or FITC with reasonable release. In addition, the achievable payloads are significantly higher as for carriers such as hyperbranched PGs. Short-term in vitro cytotoxicity and hemocompatibility tests on L929 cell lines show that the hybrid nanomaterial is highly biocompatible. Due to their outstanding properties, β-CD-g-PG hybrid nanomaterials...
Stiffness of knee-spanning external fixation systems for traumatic knee dislocations: A biomechanical study
, Article Journal of Orthopaedic Trauma ; Volume 24, Issue 11 , Nov , 2010 , Pages 693-696 ; 08905339 (ISSN) ; Firoozbakhsh, K ; Prevost, M ; Mulkey, P ; Decoster, T. A ; Schenck, R ; Sharif University of Technology
2010
Abstract
Objective: The purpose of this study was to compare the relative stiffness of four common external fixation (XF) configurations used to span and stabilize the knee after knee dislocation. Methods: Synthetic composite femora and tibiae connected with cords were used to simulate a knee. Four configurations of external fixation were tested: anterior femoral pins with monotube (XF1), anterolateral femoral pins with monotube (XF2), anterolateral femoral pins with two connecting rods (XF3), and hinged ring fixator (XF4). Six specimens of each configuration were loaded nondestructively in varus/valgus, anterior-to- posterior shear, flexion/extension, axial compression, internal/external torsion,...