Victor V. Jinga

The two step nanotube formation on TiZr as scaffolds for cell growth

Various TiO2 nanotubes on Ti50Zr alloy have been fabricated via a two step anodization method in glycol with 15vol.% H2O and 0.2M NH4F under anodization controlled voltages of 15, 30 and 45V. A new sonication treatment in deionized water with three steps and total sonication time as 1min was performed after the first anodization step in order to remove the oxide layer grown during 2h. The second step of anodization was for 1h and took place at the same conditions. The role of removed layer as a nano-prepatterned surface was evidenced in the formation of highly ordered nanotubular structures and morphological features were analyzed by SEM, AFM and surface wettability. The voltage-controlled anodization leads to various nanoarhitectures, with diameters in between 20 and 80nm. As biological assay, cell culture tests with MG63 cell line originally derived from a human osteosarcoma were performed. A correlation between nanostructure morphological properties as a result of voltage-controlled anodization and cell response was established.

Osteoblast ontogeny and implications for bone pathology: an overview.

Osteoblasts are specialized mesenchyme-derived cells accountable for bone synthesis, remodelling and healing. Differentiation of osteoblasts from mesenchymal stem cells (MSC) towards osteocytes is a multi-step process strictly controlled by various genes, transcription factors and signalling proteins. The aim of this review is to provide an update on the nature of bone-forming osteoblastic cells, highlighting recent data on MSC—osteoblast—osteocyte transformation from a molecular perspective and to discuss osteoblast malfunctions in various bone diseases. We present here the consecutive stages occurring in the differentiation of osteoblasts from MSC, the transcription factors involved and the role of miRNAs in the process. Recent data concerning the pathogenic mechanisms underlying the loss of bone mass and architecture caused by malfunctions in the synthetic activity and metabolism of osteoblasts in osteoporosis, osteogenesis imperfecta, osteoarthritis and rheumatoid arthritis are discussed. The newly acquired knowledge of the ontogeny of osteoblasts will assist in unravelling the abnormalities taking place during their differentiation and will facilitate the prevention and/or treatment of bone diseases by therapy directed against altered molecules and mechanisms.

In Vitro Biocompatibility of Human Endothelial Cells with Collagen-Doxycycline Matrices

The aim of this study was to test the biocompatibility between collagen-doxycycline matrices with various porosities and human endothelial cells. Collagen matrices were prepared by freeze-drying process. The crosslinking degree of collagen matrices was evaluated by FT-IR spectroscopy, the matrices morphology by SEM microscopy. The biocompatibility of collagen matrices with endothelial cells was monitored byfluorescence and transmission electron microscopy. We found that the three-dimensional structures of matrix with 1.2% collagen, 0.2% doxycycline crosslinked with 0.25% glutaraldehyde was optimal in terms of biodegradability, morphology and endothelial cells biocompatibility indicating the use of these scaffolds in tissueengineering.

Natural Polymer-Cell Bioconstructs for Bone Tissue Engineering

The major goal of bone tissue engineering is to develop bioconstructs which substitute the functionality of damaged natural bone structures as much as possible if critical-sized defects occur. Scaffolds that mimic the structure and composition of bone tissue and cells play a pivotal role in bone tissue engineering applications. First, composition, properties and in vivo synthesis of bone tissue are presented for the understanding of bone formation. Second, potential sources of osteoprogenitor cells have been investigated for their capacity to induce bone repair and regeneration. Third, taking into account that the main property to qualify one scaffold as a future bioconstruct for bone tissue engineering is the biocompatibility, the assessments which prove it are reviewed in this paper. Forth, various types of natural polymer- based scaffolds consisting in proteins, polysaccharides, minerals, growth factors etc, are discussed, and interaction between scaffolds and cells which proved bone tissue engineering concept are highlighted. Finally, the future perspectives of natural polymer-based scaffolds for bone tissue engineering are considered.

In Vitro Biocompatibility of Si Alloyed Multi-Principal Element Carbide Coatings.

In the current study, we have examined the possibility to improve the biocompatibility of the (TiZrNbTaHf)C through replacement of either Ti or Ta by Si. The coatings were deposited on Si and 316L stainless steel substrates by magnetron sputtering in an Ar+CH4 mixed atmosphere and were examined for elemental composition, chemical bonds, surface topography, surface electrical charge and biocompatible characteristics. The net surface charge was evaluated at nano and macroscopic scale by measuring the electrical potential and work function, respectively. The biocompatible tests comprised determination of cell viability and cell attachment to the coated surface. The deposited coatings had C/(metal+Si) ratios close to unity, while a mixture of metallic carbide, free-carbon and oxidized species formed on the film surface. The coatings’ surfaces were smooth and no influence of surface roughness on electrical charge or biocompatibility was found. The biocompatible characteristics correlated well with the electrical potential/work function, suggesting a significant role of surface charge in improving biocompatibility, particularly cell attachment to coatings surface. Replacement of either Ti or Ta by Si in the (TiZrNbTaHf)C coating led to an enhanced surface electrical charge, as well as to superior biocompatible properties, with best results for the (TiZrNbSiHf)C coating.

Collagen—Dexamethasone and Collagen-D3 Scaffolds for Bone Tissue Engineering

The aim of the study was to test the biocompatibility and osteoinductive potential of collagen with dexamethasone (Dex) and collagen with 1, 25 dihydroxycholecalciferol (D3) scaffolds on two human osteoblast cell lines, MG63 and hFOB1.19. The cell morphology was examined by SEM, the scaffolds colonization was monitored by fluorescence microscopy, viability by MTT assay and cells differentiation by PCR. The two utilized scaffolds sustained biointegration/proliferation of human osteoblast cells. However, collagen-Dex and collagen-D3 scaffolds promoted osteogenic activity of MG63 cells incresing the gene expression of osteonectine, osteocalcin and BSP II whereas no osteoinductive effect on hFOB1.19 cells was detected.

New Scaffold Structure Based on Collagen. Fabrication and Biocompatibility Evaluation

Development of bioactive material template for in vitro and in vivo synthesis of osteoinductive and biodegradable bone material was intensevely studied over the last decade and the research in the field of partial substitution of bone tissue, use a very large range of natural and synthetic polymers, inorganic components and their composites. Despite of composites collagen hydroxiapatite with a mimetic osseous composition until now was not defined a scaffold model suitable to biofunctionality of native osseous structure. The goal of the article is fabrication of a new scaffold structure, based on collagen fibrils with length 1–1.5 cm, thikness 0.1–0.3 and having a shroud structure. Collagen crosslinking was performed with aldehides in such way that aminic groups became bloked and carboxylic groups remain free in order to involve hydroxiapatite and biocompatible synthetic polymer (polyvinil alchol, polilactide) coupling. Crosslinking temperature for collagen fibrils is 70°C being a suitable temperature for resistance to “in vivo” resorbtion. Infrared spectra was performed and the amount of the hidroxyl bonds was correlated with hydrophilic [2] balance estimated from contact angle measurements. The morphology and the surface composition were determined with an Environmental Scanning Electron Microscope FEI/Phillips XL30 ESEM and all physical chemical properties especially surface features were used as basic factors in future cell growth and proliferation process. The main aim of biocompatibility tests is to multiply and to differentiate cells in vitro in osteoblasts from marrow. The environment of culture was supplemented with specific media containing Na β glicerofosfat and the cell was differentiated in osteoblasts. As arguments for differentiation were proposed the evidence of specific markers: osteonectine, sialoproteines and osteocalcine. Osteoprogenitors cells culture were tested on various samples of scaffold. Cell cultures were tested for alkaline phosphatase at a week after culture. The technique uses p-nitrophenole which is going to be change by alkaline phosphatase in dinitro-phenole.