Sharif Digital Repository

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... 

Controlling topographic features at all length scales is of great importance for the interaction of cells with tissue regenerative materials. We utilized an indirect three-dimensional printing method to fabricate polymeric scaffolds with pre-defined and controlled external and internal architecture that had an interconnected structure with macro- (400-500 μm) and micro- (∼25 μm) porosity. Polycaprolactone (PCL) was used as model system to study the kinetics of tissue growth within porous scaffolds. The surface of the scaffolds was decorated with TiO2 and bioactive glass (BG) nanoparticles to the better match to nanoarchitecture of extracellular matrix (ECM). Micrometric BG particles were... 

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... 

Hydroxyapatite (HA) is the most substantial mineral constituent of a bone which displays splendid biocompatibility and bioactivity 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) was employed as a matrix and hydroxyapatite nanorods were used as a reinforcement element of the composite. HA/PCL nanocomposites were synthesized by a new in-situ sol-gel process using low cost chemicals. Chemical and physical characteristics of the nanocomposite were studied by X-ray diffraction (XRD),... 

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... 

Reduced graphene oxide nanoplatelets (rGONPs) were synthesized by sonication of covalently PEGylated GO sheets followed by a chemical reduction using hydrazine and bovine serum albumin. Human mesenchymal stem cells (hMSCs), as a fundamental factor in tissue engineering, were isolated from umbilical cord blood (as a recently proposed source for extracting fresh hMSCs) to investigate, for the first time, the size-dependent cyto- and geno-toxic effects of the rGONPs on the cells. The cell viability test showed significant cell destructions by 1.0 μg/mL rGONPs with average lateral dimensions (ALDs) of 11±4 nm, while the rGO sheets with ALDs of 3.8±0.4 μm could exhibit a significant cytotoxic... 

Open-pore titanium scaffolds were fabricated by sintering of compressed mixtures of TiH1.924 and urea. Spherical and irregular shaped space holders were used to investigate the effect of pore shape on cellular behavior. After removal of the space holder, the shape of the spacers was replicated to the pores. Average diameter of the pores was in the range of 300-600 lm. SEM images showed that titanium hydride resulted in higher surface roughness and larger micro porosities than pure titanium. In vitro evaluationswere carried out by using MTT assay, measuring alkaline phosphatase activity and alizarin red staining in flow perfusion bioreactor for cell culture. Observations revealed excellent... 

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... 

Rapid prototyping is a promising technique for producing tissue engineering scaffolds due to its capacity to generate predetermined forms and structures featuring distinct pore architectures. The objective of this study is to investigate the influences of different pore geometries and their orientation with respect to the compressive loading direction on mechanical responses of scaffolds. Plastic models of scaffolds with cubic and hexagonal unit cells were fabricated by three-dimensional (3-D) printing. An in situ imaging technique was utilized to study the progressive compressive deformation of the scaffold models. In both cubic and hexagonal geometries, organized buckling patterns relevant... 

Bone Tissue Engineering (BTE) composed of three main parts: scaffold, cells and signaling factors. Several materials and composites are suggested as a scaffold for BTE. Biocompatibility is one of the most important property of a BTE scaffold. In this work synthesis of a novel nanocomposite including layered double hydroxides (LDH) and gelatin is carried out and its biological properties were studied. The co-precipitation (pH=11) method was used to prepare the LDH powder, using calcium nitrate, Magesium nitrate and aluminum nitrate salts as starting materials. The resulted precipitates were dried. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron... 

Design and development of biodegradable scaffolds with highly uniform and controlled internal structure that stimulate tissue regeneration are the focus of many studies. The aim of this work is to apply a modified three-dimensional (3D) printing process to fabricate polymer-matrix composites with controlled internal architecture. Computationally-designed plaster molds with various pore sizes in the range of 300-800. μm were prepared by employing 3D printing of a water-based binder. The molds were converted to ε-polycaprolactone (PCL) and PCL/bioactive glass (BG) composite scaffolds by solvent casting and freeze drying methods. Optical and electron microscopy studies revealed that the pore... 

Hydrogels made of natural polymers [chitosan (CS) and gelatin (G)] have been prepared having mechanical properties similar to those of muscle tissues. In this study, the effect of polymer concentration and scaffold stiffness on the behavior of seeded muscle-derived cells (MDCs) on the CS-G hydrogel sheets has been evaluated. Both variables were found to be important in cell viability. Viability was assessed by observation of the cell morphology after 1 day as well as a 14-day MTT assay. The CS-G hydrogels were characterized using Fourier transform infrared (FTIR) analysis, which revealed evidences of strong intermolecular interactions between CS and G. Hydrogel samples with intermediate... 

Polyethylene oxide (PEO)/chitosan (CS)/graphene oxide (GO) electrospun nanofibrous scaffolds were successfully developed via electrospinning process for controlled release of doxorubicin (DOX). The SEM analysis of nanofibrous scaffolds with different contents of GO (0.1, 0.2, 0.5 and 0.7 wt.%) indicated that the minimum diameter of nanofibers was found to be 85 nm for PEO/CS/GO 0.5% nanofibers. The π-π stacking interaction between DOX and GO with fine pores of nanofibrous scaffolds exhibited higher drug loading (98%) and controlled release of the DOX loaded PEO/CS/GO nanofibers. The results of DOX release from nanofibrous scaffolds at pH 5.3 and 7.4 indicated strong pH dependence. The... 

Highly conductive polypyrrole/graphene (PYG) nanocomposite was synthesized with chemical oxidation process via emulsion polymerization and used for the preparation of novel porous conductive gelatin/chitosan-based scaffolds. The effect of PYG loading on various properties of scaffolds was investigated. The obtained results indicated that by introducing PYG into the polymeric matrix, the porosity and swelling capacity decreased while electrical conductivity and Young's modulus demonstrated increasing trend. The in vitro biodegradation test revealed that pure gelatin/chitosan matrix lost 80% of its weight after six weeks in the presence of lysozyme whilst the biodegradation rate was... 

In the present study, polylactic acid (PLA)/polyethylene glycol (PEG)/multiwalled carbon nanotube (MWCNT) electrospun nanofibrous scaffolds were prepared via electrospinning process and their applications for the anticancer drug delivery system were investigated. A response surface methodology based on Box-Behnken design (BBD) was used to evaluate the effect of key parameters of electrospinning process including solution concentration, feeding rate, tip-collector distance (TCD) and applied voltage on the morphology of PLA/PEG/MWCNT nanofibrous scaffolds. In optimum conditions (concentration of 8.15%, feeding rate of 0.2 mL/h, voltage of 18.50 kV and TCD of 13.0 cm), the minimum experimental... 

Recently, biodegradable polymers such as starch based blends have been well renowned in the biomedical field. Studies have considered them suitable for bone scaffolds, bone cements, tissue engineering scaffolds, drug delivery systems and hydrogels. The aim of this study was to synthesize nanocomposite biomaterial consisting a blend of thermoplastic starch and ethylene vinyl alcohol as the polymer matrix, and nano-structured forsterite as the ceramic reinforcing phase for bone tissue engineering applications. Furthermore, vitamin E was applied as a thermal stabilizer during melt compounding. Extrusion and injection molding were incorporated for melt blending and shaping of samples,... 

The formation of biomimetic bone-like apatite layers throughout the biopolymer-based hydrogel scaffold is an attractive approach in bone tissue engineering. Here, the starch scaffold was prepared using a combination of particulate leaching and freeze-drying techniques. The fabricated structures were then modified by citric acid to investigate the formation of bone-like apatite layer on the porous citrate-based scaffold after soaking in simulated body fluid (SBF). The Fourier Transform Infrared (FTIR) spectra and X-ray diffraction (XRD) patterns revealed that the B-type carbonated apatite has successfully deposited on the scaffold after immersing in SBF for 28 days. Indeed, high chemical... 

Graphene oxide foam (GOF) layers with thicknesses of ∼15-50 μm and density of ∼10 graphene oxide (GO) sheets/μm were fabricated by precipitation of chemically exfoliated GO sheets in an aqueous suspension at ∼80 °C under UV irradiation. Then, rolled GOFs with desirable scales were developed as electrically conductive 3D-scaffolds and applied in directional growth of neural fibers, through differentiation of human neural stem cells (hNSCs) into neurons under an electrical stimulation. X-ray photoelectron spectroscopy indicated that the UV irradiation resulted in partial deoxygenation of the layers. Scanning electron microscopy and Raman spectroscopy confirmed the presence of multilayer GO... 

Although graphene/stem cell-based tissue engineering has recently emerged and has promisingly and progressively been utilized for developing one of the most effective regenerative nanomedicines, it suffers from low differentiation efficiency, low hybridization after transplantation and lack of appropriate scaffolds required in implantations without any degrading in functionality of the cells. In fact, recent studies have demonstrated that the unique properties of graphene can successfully resolve all of these challenges. Among various stem cells, neural stem cells (NSCs) and their neural differentiation on graphene have attracted a lot of interest, because graphene-based neuronal tissue... 

High Density Lipoprotein (HDL) is a lipid-protein complex responsible for transporting cholesterol and triglyceride molecules, as these compounds are unable to dissolve in aqueous environments such as a bloodstream. Among the most well-known possible structures, the belt-like structure is the most common shape proposed for this vital bimolecular complex. In this structure, the protein scaffold encompasses the lipid bilayer and a planar circular structure is formed. Several HDL simulations with embedded components in the lipid section were performed. Here, we applied a series of molecular dynamic simulations using the MARTINI coarse grain force field to investigate an HDL model, with pores of...