Mojgan Zandi

Biocompatibility evaluation of nano‐rod hydroxyapatite/gelatin coated with nano‐HAp as a novel scaffold using mesenchymal stem cells

This study is devoted to fabricate a novel hydroxyapatite(HAp)/gelatin scaffold coated with nano-HAp in nano-rod configuration to evaluate its biocompatibility potential. The nano-HAp particles are needle and rod-like with widths ranging between 30 to 60 nm and lengths from 100 to 300 nm, respectively. Because of their higher surface area and higher reactivity, the nano-rod particles were distributed in gelatin much better than spherical and mixed shapes particles. The compressive modulus of the nano-HAp/gelatin scaffolds coated with nano-HAp was comparable with the compressive modulus of a human cancellous bone. The potential performance of the fabricated scaffolds as seeding media was assayed using mesenchymal stem cells (MSCs). MTT (3-(4,5-dimethylthiazol-2-yl)-1,5-diphenyl tetrazulium bromide) assays were performed on days 4 and 7 and the number of the cells per scaffold was determined. On the basis of this assay, all the studied scaffolds exhibited an appropriate environment in which the loaded cells appeared to be proliferated during the cultivation periods. In all fabricated composite scaffolds, marrow-derived MSCs appeared to occupy the scaffolds internal spaces and attach on their surfaces. According to the cell culture experiments, the incorporation of rod-like nano-HAp and coating of scaffolds with nano-HAp particles enabled the prepared scaffolds to possess desirable biocompatibility, high bioactivity, and sufficient mechanical strength in comparison with noncoated HAp samples. This research suggests that the newly developed scaffold has a potential as a suitable scaffold for bone tissue engineering.

Gelatin–GAG electrospun nanofibrous scaffold for skin tissue engineering: Fabrication and modeling of process parameters

Electrospinning is a very useful technique for producing polymeric nanofibers by applying electrostatic forces. In this study, fabrication of novel gelatin/GAG nanofibrous mats and also the optimization of electrospinning process using response surface methodology were reported. At optimization section, gelatin/GAG blend ratio, applied voltage and feeding rate, their individual and interaction effects on the mean fiber diameter (MFD) and standard deviation of fiber diameter (SDF) were investigated. The obtained model for MFD has a quadratic relationship with gelatin/GAG blend ratio, applied voltage and feeding rate. The interactions of blend ratio and applied voltage and also applied voltage and flow rate were found significant but the interactions of blend ratio and flow rate were ignored. The optimum condition for gelatin/GAG electrospinning was also introduced using the model obtained in this study. The potential use of optimized electrospun mat in skin tissue engineering was evaluated using culturing of human dermal fibroblast cells (HDF). The SEM micrographs of HDF cells on the nanofibrous structure show that fibroblast cells can highly attach, grow and populate on the fabricated scaffold surface. The electrospun gelatin/GAG nanofibrous mats have a potential for using as scaffold for skin, cartilage and cornea tissue engineering.

Cell-loaded gelatin/chitosan scaffolds fabricated by salt-leaching/lyophilization for skin tissue engineering: In vitro and in vivo study

In this study, physical and biological features of the novel three-dimensional cell-loaded gelatin (G)/chitosan (CS) scaffolds fabricated via combining salt-leaching and lyophilization technique is evaluated. To fabricate these scaffolds, CS and G solutions were blended at different ratios and the influence of G/CS ratio on physical and biological properties of the scaffolds were studied. The properties of porous structure, such as microstructure, porosity, mean pore size, phosphate buffer saline solution absorption, mechanical properties as well as biocompatibility were evaluated. The in vitro assays showed excellent cell attachment and proliferation on scaffolds with G/CS ratio of 80/20. The results showed that the amount of G has a significant effect on attachment, growth, and proliferation of fibroblast cells on the scaffolds. In vivo assessment showed that treatment with human dermal fibroblast cell loaded scaffolds significantly accelerated wounds healing in rat compared with the control groups. The biological investigation on these scaffolds proves that they have a great potential for using in skin tissue engineering.

Synthesis and characterization of curcumin segmented polyurethane with induced antiplatelet activity

The main goal of this study is the synthesis of hemocompatible polyurethane elastomer containing curcumin by the reaction of poly(ξ-caprolactone) (PCL), and 1,6-hexamethylene diisocyanate (HDI), which was chain extended with varying molar ratios of 1,4-butandiol (BDO), and curcumin. Molecular structure of the synthesized polyurethane was confirmed using FT-IR and 1HNMR spectroscopy techniques. The effect of curcumin on characteristics of the synthesized polymers was analyzed by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), tensile testing, and also water contact angle measurement (WCA). The influence of curcumin on antiplatelet behavior of the curcumin extended elastomer was confirmed by static platelet adhesion (SPA) test and the number of the adhered platelets was determined using the lactate dehydrogenase (LDH) assay, in comparison with the polymer extended solely with BDO. Thermal and mechanical properties as well as hydrophobicity are enhanced through increasing curcumin content. Overall, improvement in mentioned properties led to enhanced antiplatelet behavior of curcumin containing segmented PU elastomers (PUcs).

Gelatin/chondroitin sulfate nanofibrous scaffolds for stimulation of wound healing: In‐vitro and in‐vivo study

In this research, fabrication of gelatin/chondroitin sulfate (GAG) nanofibrous scaffolds using electrospinning technique for skin tissue engineering was studied. The influence of GAG content on chemical, physical, mechanical and biological properties of the scaffolds were investigated. Human dermal fibroblast (HDF) cells were cultured and bioactivity of electrospun gelatin/GAG scaffolds for skin tissue engineering was assayed. Biological results illustrated that HDF cells attached and spread well on gelatin/GAG nanofibrous scaffolds displaying spindle-like shapes and stretching. MTS assay was performed to evaluate the cell proliferation on electrospun gelatin/GAG scaffolds. The results confirmed the influence of GAG content as well as the nanofibrous structure on cell proliferation and attachment of substrates. The gelatin/GAG nanofibrous scaffolds with the desired thickness for in-vivo evaluations were used on the full-thickness wounds. Pathobiological results showed that cell loaded gelatin/GAG scaffolds significantly accelerated wounds healing.

Nanotopographical control of human embryonic stem cell differentiation into definitive endoderm

Derivation of definitive endoderm (DE) from human embryonic stem cells (hESCs) can address the needs of regenerative medicine for endoderm-derived organs such as the pancreas and liver. Fibrous substrates which topographically recapitulate native extracellular matrix have been known to promote the stem cell differentiation. However, the optimal fiber diameter remains to be determined for the desired differentiation. Here, we have developed a simple method to precisely fabricate electrospun poly(ε-caprolactone) fibers with four distinct average diameters at nano- and microscale levels (200, 500, 800, and 1300 nm). Human ESCs were cultured as clumps or single cells and induced into DE differentiation to determine the optimal topography leading to the promoted differentiation compared with planar culture plates. Gene expression analysis of the DE-induced cells showed significant upregulation of DE-specific genes exclusively on the 200-nm fibers. By Western blot analysis, significant expression of DE-specific proteins was found when hESCs were cultured on the 200 nm substrate as single cells rather than clumps, probably due to more efficient cell-matrix interaction realized by morphological observations of the cell colonies. The results indicated that nanofibrillar substrates, only at ultrathin fiber diameters, provided a better environment for DE differentiation of hESC, which holds great promise in prospective tissue engineering applications.

Photo-crosslinkable cyanoacrylate bioadhesive: Shrinkage kinetics, dynamic mechanical properties, and biocompatibility of adhesives containing TMPTMA and POSS nanostructures as crosslinking agents†

The study investigates the photo-polymerization shrinkage behavior, dynamic mechanical properties, and biocompatibility of cyanoacrylate bioadhesives containing POSS nanostructures and TMPTMA as crosslinking agents. Adhesives containing 2-octyl cyanoacrylate (2-OCA) and different percentages of POSS nanostructures and TMPTMA as crosslinking agents were prepared. The 1-phenyl-1, 2-propanedione (PPD) was incorporated as photo-initiator into the adhesive in 1.5, 3, and 4 wt %. The shrinkage strain of the specimens was measured using bonded-disk technique. Shrinkage strain, shrinkage strain rate, maximum and time at maximum shrinkage strain rate were measured and compared. Mechanical properties of the adhesives were also studied using dynamic mechanical thermal analysis (DMTA). Biocompatibility of the adhesives was examined by MTT method. The results showed that shrinkage strain increased with increasing the initiator concentration up to 3 wt % in POSS-containing and 1.5 wt % in TMPTMA-containing specimens and plateaued out at higher concentrations. By increasing the crosslinking agent, shrinkage strain, and shrinkage strain rate increased and the time at maximum shrinkage strain rate decreased. The study indicates that the incorporation of crosslinking agents into the cyanoacrylate adhesives resulted in improved mechanical properties. Preliminary MTT studies also revealed better biocompatibility profile for the adhesives containing crosslinking agents comparing to the neat specimens.

Designing and fabrication of curcumin loaded PCL/PVA multi-layer nanofibrous electrospun structures as active wound dressing

Active wound dressings play a significant role in burn and chronic wound treatment. In this study, electrospinning process is used to fabricate a novel three-layer active wound dressing based on ε-polycaprolactone (PCL), polyvinylalcohol (PVA), and curcumin (CU) as a biologically active compound. The main purpose for developing such a system is to control wound exudates, which remains a challenge, as well as enjoying the anti-bacterial property. Electrospinning process parameters are optimized by response surface methodology to achieve appropriate nanofibrous electrospun mats, and then, a three-layer dressing has been designed in view of water absorbability, anti-bacterial, and biocompatibility characteristics of the final dressing. The results illustrate that a three-layer dressing based on PCL/curcumin containing PVA as a middle layer with optimized thickness which is placed over the incision, absorbs three times exudates in comparison with pristine dressing. Anti-bacterial tests reveal that the dressing containing 16% curcumin exhibits anti-bacterial activity without sacrificing the acceptable level of cell viability.

Rationalization of specific structure formation in electrospinning process: Study on nano‐fibrous PCL‐ and PLGA‐based scaffolds

Formation of specific structures on poly-ɛ-caprolactone (PCL) and poly lactide-co-glycolide (PLGA) based electrospun mats is rationalized and the effect of interactive parameters; high voltage and flow rate on unique surface topography is evaluated. By increasing the collecting time in electrospinning process and enhancing fiber to fiber repulsion, surface characteristics of mats changes from nano- to micro-topography. In this study surface topography of the fabricated mats based on PCL and PLGA were assessed using AFM and SEM techniques to display the distinct phenomenon occurs on collected random fibers. In this research the rationale behind the formation of bump and flower like structures on fibrous mats was discussed. Because of great potential application of the fabricated substrates in the fields of medical purposes, cell-matrix interaction was evaluated and in vitro biological test with human dermal fibroblast and mouse L929 fibroblast cells was performed to study the cell responses to different roughness of nano-fibers collected at different time intervals. Our results show that after 7 days, cell proliferation is improved on PCL collected at 40 min in the case of human fibroblast cells and on PCL collected in 70 min in the case of L929 mouse fibroblast cells.

Cell Attachment and Viability Study of PCL Nano-fiber Modified by Cold Atmospheric Plasma.

The field of tissue engineering is an emerging discipline which applies the basic principles of life sciences and engineering to repair and restore living tissues and organs. The purpose of this study was to investigate the effect of cold and non-thermal plasma surface modification of poly (ϵ-caprolactone) (PCL) scaffolds on fibroblast cell behavior. Nano-fiber PCL was fabricated through electrospinning technique, and some fibers were then treated by cold and non-thermal plasma. The cell–biomaterial interactions were studied by culturing the fibroblast cells on nano-fiber PCL. Scaffold biocompatibility test was assessed using an inverted microscope. The growth and proliferation of fibroblast cells on nano-fiber PCL were analyzed by MTT viability assay. Cellular attachment on the nano-fiber and their morphology were evaluated using scanning electron microscope. The result of cell culture showed that nano-fiber could support the cellular growth and proliferation by developing three-dimensional topography. The present study demonstrated that the nano-fiber surface modification with cold plasma sharply enhanced the fibroblast cell attachment. Thus, cold plasma surface modification greatly raised the bioactivity of scaffolds.