Key Engineering Materials Vols. 361-363

Abstract: The biological behavior of a new bioactive material composed of calcium-deficient hydroxyapatite, octacalcium phosphate, and β-tricalcium phosphate was investigated by in vitro indirect and direct cytotoxicity, cell adhesion and proliferation tests, and by in vivo subcutaneous and bone implantation in rats. The results of the in vitro studies showed that the material is biocompatible and no cytotoxic. Slightly poorer initial cell adhesion and lower cell proliferation than in control was observed, which were attributed to the reactivity and roughness of the material surface. In vivo results showed that the material is biodegradable and bioactive in bone tissue, but only biocompatible and partially biodegradable in soft tissue.

Abstract: This paper it supposed to demonstrate how to obtain the hydroxylapatite on the surface of TiAlNb biomaterial used as dental implant. The bone-forming bioactivity of TiAlNb is associated with its chemical and structural properties, including composition, porosity, specific surface area and particle size. After different bioactivation surface treatments as chemical and electrochemical treatments, it was observed a better stability for the TiAlNb alloy that was treated electrochemically.

Abstract: Hydroxyapatite (HA) and apatite based biomaterials are important for bone replacement. Different apatites could be produced by substituting calcium, phosphate or hydroxyl groups, resulting in new materials with different physical, chemical and biological properties. In this work we investigate the biological compatibility of apatites modified by divalent cations in cultured mammalian cells using Balb/c 3T3 fibroblasts cell line. Modified apatites, Ca9.5M0.5(PO4)6(OH)2 (M=Fe, Zn, Cu, Co, Sr, V e Pb) and Ca10(VO4)6(OH)2 were produced and characterized by FTIR, XRD and XRF. Extracts of each metal-modified apatites (0.1mg/mL of Dulbeco Modified Eagle Medium – DMEM without serum) were obtained. Cells (3x104) were exposed for 24 h/37C to the pure extract (100%). Afterwards, the number of viable cells was determined in a hemocitometer. The number of viable cells in the absence of any extract was taking as 100%. SHA didn’t present any toxicity while phenol killed 82% of the cells. In the presence of pure extract of Fe-HA or Sr- HA an increase of 70% and 20%, respectively, in the number of relative cells was observed. On the other hand, the number of residual cells after treatment with the pure extract of Pb+2, Zn+2, Co+2, and (VO4)3- was73, 65, 48, and 21%, respectively. In conclusion, cells response was strongly dependent on the metal that substitutes calcium or phosphate. Further studies are required to better understand the biological effect of these substitutions.

Abstract: The purpose of this study was to determine the effect of sintering conditions on microporosity of and cell proliferation and bone ingrowth on biphasic calcium phosphate (BCP) bioceramics. Discs were prepared from a calcium-deficient apatite preparation that upon sintering at 1050oC and above, results in a BCP with 60% hydroxyapatite (HA)/ 40% beta-tricalcium phosphate (β-TCP) ratio. The discs were divided into groups which were sintered under different conditions of heating rate (programmed vs. non-programmed) and temperature (1050°C vs. 1200°C). The discs were characterized in terms of composition (HA/β-TCP ratio), surface morphology, surface area, surface microporosity, per cent microporosity, and dissolution properties. The in vitro effect of sintering conditions on cell proliferation was determined using an established mouse fibroblast cell line (L929). Results demonstrated the following: (a) the HA/β-TCP ratio remained 60/40 regardless of sintering conditions; (b) the % microporosity, surface microporosity, surface area of the BCP and cell proliferation on the BCP significantly decreased with increasing sintering temperature, and (c) the extent of dissolution decreased with decreasing per cent microporosity. The in vivo study indicated no tissue adverse reaction and direct bone contact with the implant surface, confirming the biocompatibility of the BCP bioceramics. Resorption of the BCP and bone ingrowth was directly related to the sintering temperature: the higher the temperature, the lower the resorption and the bone ingrowth. Results of this study indicate that per cent microporosity of the BCP bioceramics affects its dissolution properties and cell response. The study demonstrates that optimum per cent microporosity elicits optimum cell response and should be considered to provide osteogenic/osteoinductive property to bioceramics.

Abstract: In order to enhance bone cell adhesion on hydroxyapatite (HA), collagen was used as a surface-grafting material on HA substrates because the collagen is a major constituent of connective tissues and has been regarded as one of the most excellent coating materials for bone bonding. First, HA disks (10mmΦ x 1mm) were prepared and then collagen was immobilbized on the HA surface using an 3-APTES coupling agent on HA disk surfaces. MC3T3-E1 osteoblasts were seeded on the collagen-grafted and non-grated HA disks and cultured in a Dulbecco’s modified eagle medium containing 10% fetal bovine serum for 4 hrs to evaluate the cell adhesion on the HA samples. The osteoblasts on the collagen-grafted sample were more spread than those on the non-grafted sample. It is believed that collagen-grafted HA surface provides suitable sites for cell attaching due to the high biocompatibility of collagen

Abstract: The relationships between donor age and gender and initial isolation yield and the osteogenic potentials of human bone marrow stromal cells (hBMSCs) have not been clearly elucidated. The authors investigated whether isolation yields and the osteogenic differentiation potentials of hBMSCs are indeed dependent on donor age or gender. Fresh bone marrow was aspirated from iliac crest of 72 donors (mean age 54.1 years; range, 23-84 years; 39 men and 33 women) undergoing total hip arthroplasty. Numbers of mononuclear cells, numbers of colony forming unit-fibroblasts (CFU-Fs) and alkaline phosphatase (ALP)-positive CFU-Fs, and numbers of BMSCs after isolation culture were not found to be significantly dependent on donor age or gender. Moreover, no significant age- or gender-related differences were observed in terms of the proliferation activities, ALP activities, and calcium contents of BMSCs during in vitro osteogenic differentiation. The data obtained from 72 human donors revealed no significant age- or genderrelated differences among hBMSCs in terms of isolation yields, proliferation activities, and osteogenic potentials.

Abstract: The unique characteristics of cell surface molecules on human bone marrow stromal cells (hBMSCs) have not been clearly elucidated. The authors characterized 19 cell surface molecules on culture-expanded hBMSCs obtained from 10 human donors, by flow cytometry, calculated the averages and standard deviations of the expression frequencies of individual surface molecules, and evaluated their expression patterns with respect to donor-dependent variations. Surface molecules expressed at frequencies of more than 80% on cells included, CD49e, CD29, CD90, CD73, CD44, CD105, and CD146, those expressed at frequencies of 20-80% included, Stro-1, CD51, CD54, CD31, CD106, CD163, and CD34, whereas CD49d, CD14, CD144, CD11b, and CD45 were expressed at less than 20%. Substantial donor-dependent variations (>10% standard deviation in expression percentage) were observed in the expressions of CD105, Stro-1, CD51, CD54, CD31, CD106, CD163, and CD34. Our results demonstrate that CD49e, CD29, CD90, CD73, and CD44 can be used as a positive marker for hBMSCs, and that CD144, CD11b, and CD45 could be used as a highly selective negative marker. However, the expressions of CD54, CD31, and CD106 observed in the present study, contradicted prior reports and thus, their expressions remain controversial.

Abstract: In present study a theoretical model was established to simulate the interaction between the adherent endothelial cell and fluid shear flow. A two-dimensional computational fluid dynamics (CFD) was conducted to solve the model equations. The results showed that the model cell was deformed under steady shear flow. It spread along the flow direction, and decreased its height. The deformation index (DI) increased with Reynolds number of applied fluid flow. The DI of the cell increased greatly when the initial contact angle (α) was smaller than 130°, and then it was less important with the increase of α. These results suggest that the fluid shear flow may play a particular role in the mechanism of cell activation and in the regulation of endothelial cells functions.

Abstract: In the field of tissue engineering for bone regeneration, there have been many studies that examined in the bone forming ability of the porous biomaterials with mesenchymal stem cells (MSCs). To promote the tissue engineering approach in clinical situation, there is a need for the establishment and standardization of evaluation methods for measuring the in vivo bone forming ability. In this study, we examined the seeding process using rat MSCs to ascertain whether it is a valid protocol for various materials. Our results showed that the cell seeding process for the fabrication method of MSCs/materials composite influenced the number and distribution of the MSCs in the materials, therefore the process is a key to show new bone formation which derived from the seeded MSCs. Here, we describe the detailed process which can show consistent new bone formation in pores of the materials.

Abstract: We have previously developed apatite-fiber scaffolds (AFSs) for bone tissue engineering using single-crystal apatite fibers and carbon beads. In the present investigation, we examined the possibility of reconstruction of a liver organoid via three-dimensional (3D) culture of hepatocytes using the AFSs and the radial-flow bioreactor (RFB), aiming to apply the scaffold as a matrix for regeneration of a real organ. FLC-4 cells were used as a model of hepatocyte. The cells were well-viable in the RFB settled with AFSs over a period for 28 d, compared with the cases of cellulose beads and apatite beads with high porosity of 85%. We conclude that the present AFS may be a promising scaffold for tissue engineering of liver.