Mohammadreza Tahriri

Preparation and surface characterization of poly-L-lysine-coated PLGA microsphere scaffolds containing retinoic acid for nerve tissue engineering: in vitro study.

The pluripotent nature and proliferative capacity of embryonic stem cells make them an attractive cell source for tissue engineering. In this study, the poly-L-lysine-coated PLGA microspheres which contain retinoic acid (RA) as an inducer factor were prepared by using a water-in-oil-in-water emulsion/solvent evaporation technique. Then, pluripotent P19 embryonic carcinoma cells were seeded on them for differentiating into neural cells. Size and surface morphology of PLGA microspheres were evaluated by scanning electron microscope (SEM). For in vitro examinations, SEM, MTT assay, immunofluorescent staining, histology and reverse transcriptase-polymerase chain reaction (RT-PCR) analyses were carried out. SEM micrographs of the scaffolds showed a diameter in range of 13-100 microm. Based on the release profiles obtained, the concentration of RA released from microspheres reached 10(-6) to 10(-7) mg/ml. MTT assay showed that the number of cells attached on coated microspheres were more in comparison with uncoated microspheres. Immunoflourescent staining and RT-PCR analyses for MapII, beta-tubulin III, Nestin and Pax6 indicated differentiation of P19 cells into neural cells on all of the samples. Finally, the counting of positive cells showed 80+/-8.8% and 72+/-6.9% of the cells expressed beta-tubulin III on the surface of coated and uncoated RA-loaded PLGA microspheres, respectively, while the 64+/-1.1% (P < 0.05) cells expressed tubulin III in group with soluble.

Development of PLGA-coated β-TCP scaffolds containing VEGF for bone tissue engineering

Bone tissue engineering is sought to apply strategies for bone defects healing without limitations and short-comings of using either bone autografts or allografts and xenografts. The aim of this study was to fabricate a thin layer poly(lactic-co-glycolic) acid (PLGA) coated beta-tricalcium phosphate (β-TCP) scaffold with sustained release of vascular endothelial growth factor (VEGF). PLGA coating increased compressive strength of the β-TCP scaffolds significantly. For in vitro evaluations, canine mesenchymal stem cells (cMSCs) and canine endothelial progenitor cells (cEPCs) were isolated and characterized. Cell proliferation and attachment were demonstrated and the rate of cells proliferation on the VEGF released scaffold was significantly more than compared to the scaffolds with no VEGF loading. A significant increase in expression of COL1 and RUNX2 was indicated in the scaffolds loaded with VEGF and MSCs compared to the other groups. Consequently, PLGA coated β-TCP scaffold with sustained and localized release of VEGF showed favourable results for bone regeneration in vitro, and this scaffold has the potential to use as a drug delivery device in the future.

The Use of Carbon Nanotubes to Reinforce 45S5 Bioglass-Based Scaffolds for Tissue Engineering Applications

Bioglass has been used for bone-filling material in bone tissue engineering, but its lean mechanical strength limits its applications in load-bearing positions. Carbon nanotubes (CNTs), with their high aspect ratio and excellent mechanical properties, have the potential to strengthen and toughen bioactive glass material without offsetting its bioactivity. Therefore, in this research, multiwall carbon nanotube (MWCNT)/45S5 Bioglass composite scaffolds have been successfully prepared by means of freeze casting process. 45S5 Bioglass was synthesized by the sol-gel processing method. The obtained material was characterized with X-ray powder diffraction (XRD). The mechanical properties of the scaffolds, such as compression strength and elastic modulus, were measured. Finally, compared with the scaffolds prepared by 100% 45S5 Bioglass powders, the addition of 0.25 wt.% MWCNTs increases the compressive strength and elastic modulus of 45S5 Bioglass scaffolds from 2.08 to 4.56 MPa (a 119% increase) and 111.50 to 266.59 MPa (a 139% increase), respectively.

Investigation of phase transition of γ-alumina to α-alumina via mechanical milling method

In this research, the results obtained from studying the phase transition of γ-alumina (γ-Al2O3) to α-alumina (α-Al2O3) during intense mechanical activation in high-energy ball milling are presented. The powder samples were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), thermogravimetric and Differential thermal analyses (TG-DTA). With respect to the results achieved from above analyses, the transition of γ → α-alumina through δ- and θ-phases, can be initiated. Also, it was found that the pure γ-alumina phase showed a great stability during high-energy ball milling and there was no transformation to any other phase after a long milling time (30 h). On the other hand, γ-alumina containing a small amount of the α-alumina seed, showed a gradual phase transition from γ-alumina to α-alumina in milling. The phase transition mechanism during milling is nucleation and growth, which is promoted by the α-alumina seed.

Effect of poly-L-lysine coating on retinoic acid-loaded PLGA microspheres in the differentiation of carcinoma stem cells into neural cells

In this study, PLGA microspheres were prepared using a water-in-oil-in-water emulsion/solvent evaporation technique. Some microspheres were coated with poly-L-lysine (an extracellular matrix (ECM) component), and then pluripotent P19 embryonic carcinoma cells were seeded on them. P19 cells attached onto the PLGA microspheres; subsequently, by adding retinoic acid (RA) to cell culture medium as a neurogenic inducer (RA was released from the microspheres), the cells differentiated into neural cells. Size and morphology of PLGA microspheres was characterized by scanning electron microscopy (SEM). Neurogenic differentiation was studied by immunofluorescent staining, real-time polymerase chain reaction (RT-PCR), and light microscopy. Histological assay showed that more cells attached onto microspheres coated with poly-L-lysine than the uncoated group. Immunofluoresent staining and RT-PCR analysis for ß-Tubulin, Nestin and Pax6 genes indicated differentiation of P19 cells into neural cells on both coated and uncoated microspheres. It was found that a high surface area of microspheres improves cell attachment and expansion, which was significantly increased in those coated with poly-L-lysine. Finally, these results highlight the versatility of these sample scaffolds as a model system for nerve tissue engineering.

RETRACTED: Sol-gel preparation, characterisation and in vitro bioactivity of Mg containing bioactive glass

Abstract This article has been retracted by the publisher. The Editor and publisher acted in good faith on the basis of the information available at the time of acceptance and remain committed to the highest ethical and scientific standards in the peer review and publication of submissions.

Green synthesis and characterisation of spherical PbS luminescent micro‐ and nanoparticles via wet chemical technique

Abstract Abstract In this research, the authors present a simple and surfactant free procedure for the synthesis of spherical lead sulphide (PbS) micro and nano particles. The X‐ray diffraction (XRD) analysis showed that the crystal structure of PbS nanocrystals (NCs) was in its cubic phase. Also, the average crystallite size using Scherrer’s formula was ∼13 nm and the calculated lattice constant using Bragg’s equation was 0·5950 nm, which was very close to the value in the standard card (JCPDS Card File No. 5‐592). In addition, the samples were characterised by scanning electron microscope (SEM), transmission electron microscope (TEM), X‐ray analyser (EDX), photoluminescence (PL) and Fourier transform infrared (FTIR). The SEM and TEM images revealed that the synthesised particles had a well defined spherical morphology. Finally, the PL study showed that the emission spectrum was a strong and narrow band with high intensity centred at 655 nm which confirmed the high quality luminescence properties of the synthesised PbS NCs.

Novel calcium hydroxide/nanohydroxyapatite composites for dental applications: in vitro study

Abstract Abstract The physical, physicochemical and antimicrobial properties of novel cement type calcium hydroxide/nanohydroxyapatite composites were evaluated by measuring setting time, compressive strength, phase analysis, pH, water solubility and bacterial inhibition zone. Different cement pastes were obtained by mixing biphasic powders (comprising mixtures of calcium hydroxide and nanohydroxyapatite in various weight ratios) and ester of salicylic acid as liquid. Cements with different amounts of nanohydroxyapatite set at approximately 4-14 min and had a compressive strength of 8-16 MPa. The crystalline phases of the set cements were hydroxyapatite and calcium hydroxide. Finally, all composite samples showed antibacterial activity, and the larger zone of bacterial inhibition was observed in composites with higher amount of Ca(OH)2.

A current overview of materials and strategies for potential use in maxillofacial tissue regeneration.

Tissue regeneration is rapidly evolving to treat anomalies in the entire human body. The production of biodegradable, customizable scaffolds to achieve this clinical aim is dependent on the interdisciplinary collaboration among clinicians, bioengineers and materials scientists. While bone grafts and varying reconstructive procedures have been traditionally used for maxillofacial defects, the goal of this review is to provide insight on all materials involved in the progressing utilization of the tissue engineering approach to yield successful treatment outcomes for both hard and soft tissues. In vitro and in vivo studies that have demonstrated the restoration of bone and cartilage tissue with different scaffold material types, stem cells and growth factors show promise in regenerative treatment interventions for maxillofacial defects. The repair of the temporomandibular joint (TMJ) disc and mandibular bone were discussed extensively in the report, supported by evidence of regeneration of the same tissue types in different medical capacities. Furthermore, in addition to the thorough explanation of polymeric, ceramic, and composite scaffolds, this review includes the application of biodegradable metallic scaffolds for regeneration of hard tissue. The purpose of compiling all the relevant information in this review is to lay the foundation for future investigation in materials used in scaffold synthesis in the realm of oral and maxillofacial surgery.

Chitosan/heparin surface modified polyacrylic acid grafted polyurethane film by two step plasma treatment

Abstract The aim of this study is to design an artificial skin dress. A multilayer skin dressing included synthesised castor oil based polyurethane (PU) as the outer layer and two biopolymeric layers of heparin and chitosan as the inner layers were prepared. The surface of PU film was activated using two steps oxygen radio frequency plasma treatment. The surface of the modified PU films characterised by attenuated total reflection Fourier transform infrared spectroscopy, scanning electron microscopy and water drop contact angle measurements. Scanning electron microscopy observations confirmed the presence of grafted poly acrylic acid on the surface of PU films. Also, heparin and chitosan were immobilised on PU films. In vitro cell culture showed that the samples have an excellent biocompatibility with L929 fibroblast cells. Cell adhesion and proliferation of cells on the chitosan/heparin immobilised surfaces showed better behaviours compared with poly (acrylic acid) grafted PU film.