Preparation and Characterization of Nanocomposite Scaffolds (Collagen/β-TCP/SrO) for Bone Tissue Engineering

BACKGROUND: Nowadays, production of nanocomposite scaffolds based on natural biopolymer, bioceramic, and metal ions is a growing field of research due to the potential for bone tissue engineering applications. METHODS: In this study, a nanocomposite scaffold for bone tissue engineering was successfully prepared using collagen (COL), beta-tricalcium phosphate (β-TCP) and strontium oxide (SrO). A composition of β-TCP (4.9 g) was prepared by doping with SrO (0.05 g). Biocompatible porous nanocomposite scaffolds were prepared by freeze-drying in different formulations [COL, COL/β-TCP (1:2 w/w), and COL/β-TCP-Sr (1:2 w/w)] to be used as a provisional matrix or scaffold for bone tissue engineering. The nanoparticles were characterized by X-ray diffraction, Fourier transforms infrared spectroscopy and energy dispersive spectroscopy. Moreover, the prepared scaffolds were characterized by physicochemical properties, such as porosity, swelling ratio, biodegradation, mechanical properties, and biomineralization. RESULTS: All the scaffolds had a microporous structure with high porosity (~ 95–99%) and appropriate pore size (100–200 µm). COL/β-TCP-Sr scaffolds had the compressive modulus (213.44 ± 0.47 kPa) higher than that of COL/β-TCP (33.14 ± 1.77 kPa). In vitro cytocompatibility, cell attachment and alkaline phosphatase (ALP) activity studies performed using rat bone marrow mesenchymal stem cells. Addition of β-TCP-Sr to collagen scaffolds increased ALP activity by 1.33–1.79 and 2.92–4.57 folds after 7 and 14 days of culture, respectively. CONCLUSION: In summary, it was found that the incorporation of Sr into the collagen-β-TCP scaffolds has a great potential for bone tissue engineering applications.

Tongue squamous cell carcinoma in a patient with systemic sclerosis: a case report

Objective: Systemic sclerosis [SS] is a chronic autoimmune disease of connective tissue, which involves skin and internal organs, and results in collagen deposition and fibroblasts activation. Studies have reported a higher risk of malignancy in patients with progressive systemic sclerosis [PSS].The aim of this study is to report a case of tongue squamous cell carcinoma [SCC] in a patient with PSS

Case: A 46-year-old woman with SS presented to the Department of Oral Medicine of Shahid Beheshti University of Medical Sciences Dental School with chief complaint of an ulcer on her tongue. During intraoral examination, an asymptomatic ulcer measuring 2.0×1.5 cm was discovered on the right lateral border of the tongue. Incisional biopsy under local anesthesia was performed and histopathological report confirmed presence of squamous cell carcinoma. After further evaluation, surgery was performed, followed by three sessions of brachytherapy and six sessions of chemotherapy. After 26 months of follow-up, there was no evidence of recurrence

Conclusion: Periodic screening examinations are necessary to discover possible malignancies in primary stages in patients with SS

Effect of chitosan grafted polyethylenimine nanoparticles as a gene carrier on mesenchymal stem cells viability

This study discusses the effect of complexes of chitosan grafted polyethylenimine[Ch-PEI] with plasmid DNA on viability of mesenchymal stem cells[MSCs] derived from human marrow. Ch-PEI/pDNA nanoparticles were synthesized through the complex coacervation method using pIRES plasmid containing Green Fluorescent Protein [GFP] gene. To confirm the complexation, samples were run through an agarose gel. Human bone marrow mesenchymal stem cells were studied for the cytotoxicity of the nanoparticles by MTT assay. MTT results indicated Ch-PEI does not have any significant cytotoxicity compared with PEI and Lipofectamine2000 leading to 40% cytotoxicity. According to the results it seems that grafting chitosan with PEI improves the MSCs viability

Organophosphorous residue in Liza aurata and Cyprinus carpio

Objective:To determine the amount of azinphos methyl and diazinon residues in two river fishes, Liza aurata and Cyprinus carpio, in the north of Iran. Methods: This study was done during 2006-2007. In this survey, 152 water and fish samples from Gorgan and Qarasu rivers, north of Iran, were investigated. Sampling was done in three predetermined stations along each river. Organophosphorus compounds (OPs) were extracted from the fishes and the water of rivers. After extraction, purification and concentration processes, the amount and type of insecticides in water and fish samples were determined by high performance thin layer chromatography (HPTLC). Results:There was a significant difference in the residue of the insecticides in the water and fish samples between summer and other seasons in the two rivers. The highest amount of insecticides residue was seen during summer. In both rivers, the amount of diazinon and azinphos methyl residues in the two fishes was more than 2 000 mg/L in summer. There was no significant difference in insecticides residue between the fishes in two rivers. The diazinon residue was higher than the standard limits in both rivers during the spring and the summer, but the residual amount of azinphos methyl was higher than the standard limits only during the summer and only in Qarasu River. Conclusions:It can be concluded that the amount of OPs in the water and the two fishes, Liza aurata and Cyprinus carpio, is higher than the permitted levels.

Study of mesenchymal stem cell proliferation and bone differentiation on composite scaffolds of PLLA and nano hydroxyapatite with different morphologies

Nowadays, bone constructs elaborated according to tissue engineering principles are being regarded as an ideal choice for the reconstruction of segmental bone defects. In this study, proliferation and bone differentiation of marrow-derived mesenchymal stem cells [MSCs] were compared in different composite scaffolds containing varying morphologies of nano hydroxyapatite [nHAP]. Needle nHAP/PLLA [poly [L-lactide acid]], spherical nHAP/ PLLA and rod nHAP/PLLA scaffolds were prepared and 3D cultures of passaged-3 rat MSCs were established using the scaffolds. The loading of the cells onto the scaffold internal spaces was confirmed with microscopy and their proliferation was determined by MTT assay. To compare the osteogenic differentiation of the cells on the scaffold surfaces, osteogenic 3D cultures were established and kept for 21 days. At the end of this period culture mineralization and relative bone-related gene expression were quantified using the alizarin red quantification assay and semi quantitative RT-PCR analysis respectively. ANOVA was used to compare the data. According to the MTT assays, cells adhered to all the studied scaffold surfaces tended to proliferate. In this respect the microenvironment provided by the needle nHAP/ PLLA appeared much better than that of either the spherical or rod nHAP/PLLA scaffolds [P<0.05]. Similarly, mineralization was observed to be heavier for the needle nHAP/PLLA scaffold compared to the two other composite scaffolds. In addition, the relative expression of coll I, osteocalcin, runx2 and ALP genes all appeared to be significantly higher in the cells cultivated on needle nHAP/PLLA scaffolds versus their spherical and rod counterparts. Overall, needle nHAP/PLLA scaffolds appear to provide the most appropriate matrix for producing bone construct using MSCs

Matrigel enhances in vitro bone differentiation of human marrow-derived mesenchymal stem cells

The use of co-culture cells as well as extra cellular matrix are among those strategies that have been employed to direct mesenchymal stem cell [MSC] bone differentiation in culture. In this regard, there is no study considering the effects of Matrigel on mesenchymal stem cell [MSC] in vitro bone differentiation. This was the subject of the present study. Human passaged-3 MSCs isolated from the marrow aspirates were seeded on either Matrigel or conventional polystyrene plastic surfaces [as control] for 10 days. To compare the cell proliferation in two cultures, the cell numbers were determined during the cultivation period. For bone differentiation, the confluent cultures from either group were provided with osteogenic medium and incubated for 21 days during which the alkaline phosphates [ALP] activity, culture mineralization and the expression of some bone-related genes were quantified and statistically compared. MTT assay indicated that Matrigel-cultivated cells underwent statistically less proliferation than polystyrene-cultivated cells [P<0.05]. Regarding the osteogenic differentiation, ALP activity was significantly high in Matrigel versus plastic cultures. Calcium deposition in Matrigel cultures tended to be significantly extensive compared with that of control cultures [2.533 +/- 0.017 versus 0.607 +/- 0.09 mM]. Furthermore, according to the semi-quantitative RT-PCR analysis, compared with polystyrene plastic surface, Matrigel seemed to provide a microenvironment in which human MSC expressed osteocalcin and collagen I genes in a significantly higher level. Collectively it seems that Matrigel could be considered as an appropriate matrix for MSC osteogenic differentiation

[Comparison of proliferation and osteoblast differentiation of marrow-derived mesenchymal stem cells on nano- and micro-hydroxyapatite contained composite scaffolds]

Bones constructed by tissue engineering are being considered as valuable materials to be used for regeneration of large defects in natural bone. In an attempt to prepare a new bone construct, in this study, proliferation and bone differentiation of marrow-derived mesenchymal stem cells [MSCs] on our recently developed composite scaffolds of nano-, micro-hydroxyapatite/poly[l-lactic acid] were compared with pure poly[l-lactic acid] scaffolds. For this purpose, some passaged-3 rat MSCs were three-dimensionally cultivated on the scaffold surfaces and their morphology was observed with scanning electron microscopy. Cell proliferations on different scaffolds were examined by MTT assays. Osteogenic cultures were established with the scaffolds loaded with MSCs for 21 days at the end of which culture mineralization; the cell alkaline phosphatase [ALP] Level and the relative expression of selected bone specific genes were quantified and compared to each other. Our results indicated that the cells having been adhered and assumed spherical morphology were able to proliferate in all studied scaffolds. The microenvironment provided by nano-scaffolds appeared much better medium than those of micro-scaffolds and pure PLLA [P < 0.05]. The osteogenesis assays indicated to the superiority of nanoscaffolds in supporting MSCs undergoing bone differentiation, which was reflected in high cellular ALP levels, increased bone-related gene expression and enhanced culture mineralization. Collectively, the bone construct prepared with nano-hydroxyapatite/ poly [llactic acid] scaffold and proliferated MSCs would be suitable candidate for use in bone regenerative medicine