Sharif Digital Repository

Herein, a hybrid hydrogel/microsphere system is introduced for accelerated wound healing by sustained release of basic fibroblast growth factor (bFGF). The hydrogel is composed of a mixture of PVA, gelatin and chitosan. The double-emulsion-solvent-evaporation method was utilized to obtain microspheres composed of PCL, as the organic phase, and PVA, as the aqueous phase. Subsequently, various in-vitro and in-vivo assays were performed to characterize the system. BSA was used to optimize the release mechanism, and encapsulation efficiency in microspheres, where a combination of 3% (w/v) PCL and 1% (w/v) PVA was found to be the optimum microsphere sample. Incorporation of microspheres within... 

The fabrication of a suitable scaffold material is one of the major challenges for bone tissue engineering. Poly(lactic acid) (PLA) is one of the most favorable matrix materials in bone tissue engineering owing to its biocompatibility and biodegradability. However, PLA suffers from some shortcomings including low degradation rate, low cell adhesion caused by its hydrophobic property, and inflammatory reactions in vivo due to its degradation product, lactic acid. Therefore, the incorporation of bioactive reinforcements is considered as a powerful method to improve the properties of PLA. This review presents a comprehensive study on recent advances in the synthesis of PLA-based biocomposites... 

Synthesis and characterization of a new series of low molecular weight (MW = 500–3000) OH-terminated linear aliphatic unsaturated polyesters based on cis-2-butene-1,4-diol and oxalic to sebacic acid were investigated. Direct polycondensation and transesterification methods were used for the syntheses. The latter was recognized to be the preferable method due to its lower reaction temperature and time, lower diol/diacid ratio, absence of decarboxylation, and formation of a product with low polydispersity (Mw/Mn = 1.3–2.7). Elemental analysis, GPC, FTIR, 1H-NMR, DSC, and WAXD were used for the investigations. A segmented polyurethane based on poly (cis-2-butylene adipate) glycol was also... 

Pervious concrete (PC) has been detecting application in pavement and concrete structures such as dams, small retaining walls, and etc during the past decades. Also, in recent years, the types of resins have been introduced to apply in concrete owing to the enhancing in mechanical and durability characteristics. However, few studies have investigated the mechanical behavior of high performance pervious concrete (HPPC) incorporated by polyester and epoxy resins as polymeric composites, where ordinary cement material has been completely deleted. The purpose of this investigation is to compare the mechanical properties, permeability, and durability of HPPCs made by polymeric composites (i.e.... 

Background: Researchers are trying to study the mechanism of neural stem cells (NSCs) differentiation to oligodendrocyte-like cells (OLCs) as well as to enhance the selective differentiation of NSCs to oligodendrocytes. However, the limitation in nerve tissue acces-sibility to isolate the NSCs as well as their differentiation toward oligodendrocytes is still challenging. Purpose: In the present study, a hybrid polycaprolactone (PCL)-gelatin nanofiber scaffold mimicking the native extracellular matrix and axon morphology to direct the differentiation of bone marrow-derived NSCs to OLCs was introduced. Materials and Methods: In order to achieve a sustained release of T3, this factor was... 

Background: This research follows some investigations through neural tissue engineering, including fabrication, surface treatment, and evaluation of novel self-stimuli conductive biocompatible and degradable nanocomposite scaffolds. Methods: Gelatin as a biobased material and polyvinylidene fluoride (PVDF) as a mechanical, electrical, and piezoelectric improvement agent were co-electrospun. In addition, polyaniline/graphene (PAG) nanoparticles were synthesized and added to gelatin solutions in different percentages to induce electrical conductivity. After obtaining optimum PAG percentage, cold atmospheric plasma (CAP) treatment was applied over the best samples by different plasma variable... 

In the present work, a new micro-solid phase extraction (μ-SPE) sorbent as an extracting medium based on core-shell nanofibers was synthesized by electrospinning. The core-shell nanofibers of polyvinylpyrrolidone-Polybutylene terephthalate/polypyrrole (PVP-PBT/PPy) were electrospun and subsequently, modified hollow nanofibers were prepared by removing the central PVP moiety. Moreover, conventional PBT/PPy was also prepared for the comparison purposes. The homogeneity and the porous surface structure of the core-shell nanofibers were confirmed by scanning electron microscopy (SEM). The applicability of the fabricated nanofibers-coating was examined by immersed μ-SPE of some selected triazine... 

We present gas sensing property of carbon nanotubes (CNTs) polymethylmethacrylate (PMMA) composite as the active element for acetone vapour detection at room temperature. The polymeric films were formed by spin coating method on SiO2 substrates. Then they were activated by dropping the CNTs suspension in acetone on the PMMA films. The CNT/PMMA films were characterised by SEM, TEM and Raman spectroscopy. Variation of film's electrical resistance after exposure polar and non-polar gases is utilised as the principle of gas sensing. The experimental results showed that the samples present chemical selectivity and reversibility toward polar gases especially acetone vapour  

Following our previous work on morphology, corrosion resistance and thermal properties of unsaturated polyester (UP)/nanoclay composites, the effect of electron beam (EB) irradiation on mechanical properties of UP/nanoclay composites with various nanoclay contents is investigated in this work. Moreover, influence of EB irradiation with doses of 100, 500 and 1000 kGy on tensile properties and hardness of nanocomposite was examined. FTIR spectroscopy was employed to examine the effect of irradiation on chemical structure of polymer. EB irradiation up to 500 kGy led to the improvement of tensile strength and hardness of the samples. The best mechanical properties were observed for the... 

Incorporating titanium dioxide (TiO2) nanoparticles into the polymeric matrix offers an opportunity to obtain nanocomposites with improved functionality. In this study, the commercial TiO2 nanoparticles (TNP) were surface treated by different concentrations of aminopropyl triethoxy silane (APTS) as a coupling agent and triethylamine (Et3N) as a surface grafting catalyst by an aqueous process to prepare a nanocomposite with superior properties. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were performed to confirm the successful surface modification of TNP. The prepared modified TiO2 nanoparticles (mTNP) with different weight fractions were used as... 

In this work, flexible thermoelectric fabrics, polyester/yarn fabrics coated with polyaniline/carbon nanotube (PANI/CNT) nanocomposite, were fabricated by sequential processing: (I) polyaniline/carbon nanotube nanocomposites preparation by a one-step in-situ polymerization and (II) dip coating of a mixture solution of CNT-doped PANI on a polyester/yarn fabric. Nanocomposites were synthesized with various CNT content (0.5, 2.5, 5, and 10 wt%) and characterized using different methods. The Seebeck coefficient and electrical conductivity measurements were used to determine their thermoelectric properties. The results revealed significant improvement in both electrical conductivity and the... 

In this work, flexible thermoelectric fabrics, polyester/yarn fabrics coated with polyaniline/carbon nanotube (PANI/CNT) nanocomposite, were fabricated by sequential processing: (I) polyaniline/carbon nanotube nanocomposites preparation by a one-step in-situ polymerization and (II) dip coating of a mixture solution of CNT-doped PANI on a polyester/yarn fabric. Nanocomposites were synthesized with various CNT content (0.5, 2.5, 5, and 10 wt%) and characterized using different methods. The Seebeck coefficient and electrical conductivity measurements were used to determine their thermoelectric properties. The results revealed significant improvement in both electrical conductivity and the... 

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... 

This study presents a bilayer structure as a skin scaffold comprised of an electrospun sheet layer made of polycaprolactone and polyvinil alcohol and a porous hydrogel layer made of chitosan and gelatin. The hydrogel layer was fabricated by employing the freeze-gelation technique. The bilayer structure was achieved by pouring the hydrogel solution on the electrospun sheet at the bottom of a mold followed by the freeze-gelation technique to obtain a porous structure in the hydrogel. The hydrogel and hydrogel-electrospun samples were characterized by scanning electron microscopy, swelling, tensile strength, in vitro and in vivo analyses. From a mechanical strength standpoint, the combination... 

The coaxial electrospinning for producing core-shell nanofibers due to control the release profile of drug by the shell layer has been developed. N-carboxymethyl chitosan (CMC)-polyvinyl alcohol (core)/poly(ε-caprolactone) (PCL) (shell) nanofibers were produced via coaxial electrospinning. Doxorubicin (DOX) and nickel ferrite nanoparticles were incorporated into the nanofibers for controlled release of DOX against MCF-7 breast cancer. The minimum CMC/PCL fiber diameter was found to be 300 nm by optimizing of three variables including voltage to distance ratio (1.5–2.5 kV/cm), CMC concentration (4−6 wt.%) and PCL concentration (8−12 wt.%). The synthesized core-shell fibers were characterized... 

The coaxial electrospinning for producing core-shell nanofibers due to control the release profile of drug by the shell layer has been developed. N-carboxymethyl chitosan (CMC)-polyvinyl alcohol (core)/poly(ε-caprolactone) (PCL) (shell) nanofibers were produced via coaxial electrospinning. Doxorubicin (DOX) and nickel ferrite nanoparticles were incorporated into the nanofibers for controlled release of DOX against MCF-7 breast cancer. The minimum CMC/PCL fiber diameter was found to be 300 nm by optimizing of three variables including voltage to distance ratio (1.5–2.5 kV/cm), CMC concentration (4−6 wt.%) and PCL concentration (8−12 wt.%). The synthesized core-shell fibers were characterized... 

In this work, the synthesized graphene oxide/TiO2/doxorubicin (GO/TiO2/DOX) composites were loaded into the chitosan/poly(lactic acid) (PLA) solutions to fabricate the electrospun chitosan/PLA/GO/TiO2/DOX nanofibrous scaffolds via electrospinning process. The synthesized composites and nanofibers were characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis. Three-factor three-level central composite design was used to determine the influence of PLA to chitosan ratio, TiO2/DOX content and GO/TiO2/DOX content on the release of DOX from nanofibrous scaffolds. Drug loading efficiency and drug release behavior from... 

In this study, polyaniline nanoparticles (PANI NPs) in emeraldine base (EB) form were prepared by a modified method and characterized by FTIR and UV–vis spectroscopies. The average size of the nanoparticles was 140 nm measured by DLS method. The nanoparticles were embedded into polylactic acid (PLA) nanofibers prepared by electrospinning method. It was found that inclusion of PANI NPs in PLA resulted in reduced diameter of the fibers during the electrospinning process. Also, the surface of nanofibers appeared smooth in FE-SEM images without formation of beads. Improvement in mechanical and electrical properties of PLA/PANI nanofibers over the neat PLA nanofibers implied a good dispersion of... 

Commercially available track-etched polyester membranes were used as templates to electrodeposit Co-Ni-Cu/Cu multilayered nanowires, giving room-temperature current perpendicular to plane (CPP) giant magnetoresistance (GMR) values of up to ∼12%. In contrast to similar nanowires electrodeposited in track-etched polycarbonate membranes, the GMR obtained in multilayered nanowires electrodeposited in the polyester membranes increased with decreasing Cu-layer thickness tCu, for tCu in the 2-7 nm range, indicating a lack of ferromagnetic coupling through pinholes, etc. Transmission electron micrographs showed clear evidence for smooth, parallel layer interfaces in the nanowires. © 2006 Elsevier... 

Organ-on-a-chip technology tries to mimic the complexity of native tissues in vitro. Important progress has recently been made in using this technology to study the gut with and without microbiota. These in vitro models can serve as an alternative to animal models for studying physiology, pathology, and pharmacology. While these models have greater physiological relevance than two-dimensional (2D) cell systems in vitro, endocrine and immunological functions in gut-on-a-chip models are still poorly represented. Furthermore, the construction of complex models, in which different cell types and structures interact, remains a challenge. Generally, gut-on-a-chip models have the potential to...