Biomedical subjects

A El-Ghannam

Publications and source records attributed to A El-Ghannam.

8 recordsLinked to original sources

PubMed2006

Effect of bioactive ceramic dissolution on the mechanism of bone mineralization and guided tissue growth in vitro.

A major objective of this research work was to evaluate the effect of bone cells on the dissolution-precipitation reaction in vitro. Rat bone marrow stem cells were seeded on silica-calcium phosphate nano composite (SCPC) with different chemical compositions and crystalline structures. Measurements of the Ca, P, Si, and Na concentrations in the tissue culture media using inductively coupled plasma indicated that bone marrow stem cells attached to the surface of SCPC did not affect the dissolution behavior of the material. However, bone marrow stem cells interfered with the back precipitation reaction and inhibited the formation of a calcium phosphate (Ca-P) layer on the material surface. Scanning electron microscope-energy-dispersive X-ray analyses showed that, in the absence of cells, a Ca-P layer formed on the material surface because of the dissolution-precipitation reaction. Bone cells attached to SCPC that contains high silica content absorbed significantly higher concentrations of medium Ca than cells attached to SCPC that contains low silica content. In conjunction with the absorption of high Ca concentration, attached bone marrow stem cells produced calcified nodules and mineralized extracellular matrix, indicating osteoblastic differentiation. Results of the study strongly suggest that the mechanism of bone mineralization at the interface with bioactive ceramics is mainly cell mediated and is enhanced by the absorption of critical concentrations of dissolved Ca and P. The silicon-rich phase also provided a guided cell adhesion and tissue growth in vitro. The enhanced bioactivity reactions and strong stimulatory effect on bone cell function are attributed to the modified crystalline structure of the SCPC material.

Animals↗

PubMed2005

Effects of silica on the bioactivity of calcium phosphate composites in vitro.

In the present study, silica-calcium phosphate composites (SiO(2)-CaP composites) were developed by mixing the starting materials (SiO(2) and CaHPO(4)) in different ratios with the addition of 0.1% w/v NaOH solution. The phase composition of the SiO(2)-CaP composites was determined by XRD and FTIR. After thermal treatment at 350 degrees C/1 h and at 1000 degrees C/3.5 h; all SiO(2)-CaP composites composed of beta-quartz, alpha-cristobalite and beta-Ca2P2O7. The presence of calcium phosphate enhanced the transformation of beta-quartz into alpha-cristobalite at 1000 degrees C. SEM observation indicated favorable attachment and spreading of neonatal rat calvaria osteoblasts onto the surface of silica-rich SiO(2)-CaP composites. After attachment, these cells produced significantly higher amount of protein and expressed higher AP activity than cells attached to silica-poor samples. Results of the study suggested that the silica-based composites are more bioactive than calcium phosphate-based composites. Silica promoted the expression of osteoblast phenotype by both solution-mediated effect and direct interaction with the surface of the substrate.

Alkaline Phosphatase↗

PubMed2004

Cyclosilicate nanocomposite: a novel resorbable bioactive tissue engineering scaffold for BMP and bone-marrow cell delivery.

Porous bioactive resorbable silica-calcium phosphate nanocomposite (SCPC) was prepared by a sintering technique. XRD analyses showed that the main crystalline phases of the SCPC are Na(3)CaPSiO(7) (clinophosinaite), beta-NaCaPO(4) (rhenanite), Na(2)CaSiO(4), and beta-quartz (SiO(2)). The clinophosinaite is a novel cyclosilicate bioactive mineral that enhanced the mechanical and bioactivity properties of the SCPC. TEM analysis showed that the grain sizes of the multiphase SCPC are in the nanometer scale. Moreover, the SCPC was engineered with nano- and microscale porosity. The SCPC had significantly higher compressive strength than porous hydroxyapatite (HA). FTIR analyses revealed the formation of biological hydroxyapatite layer on the SCPC surface after 4 days of immersion in SBF. When SCPC was loaded with rhBMP-2, it provided a superior release profile of biologically active rhBMP-2 compared to porous HA. Bone-marrow cells incubated with medium treated with the rhBMP-2 released from the SCPC-rhBMP-2 hybrid expressed significantly higher alkaline phosphatase activity than that expressed by cells incubated with media treated with rhBMP-2 released from HA-rhBMP-2. In addition, cells attached to the SCPC-rhBMP-2 hybrid produced mineralized extracellular matrix (ECM) and bone-like tissue that covered the material surface and filled pores in the entire thickness of the template after 3 weeks in culture. In contrary, cells attached to the HA-rhBMP-2 produced limited amount of unmineralized ECM after the same time period. Results of the study strongly suggest that the porous bioactive silica-calcium phosphate nanocomposite can serve as a delivery system for cells and biological molecules. The SCPC-rhBMP-2-marrow cell hybrid may serve as an alternative to autologous bone grafting.

Absorption↗

PubMed2004

Crystallization behavior of silica-calcium phosphate biocomposites: XRD and FTIR studies.

Silica and calcium phosphates (CaP) are the most important ingredients in bioactive materials that bond to bone and enhance bone tissue formation. In this study, silica-calcium phosphate (SiO2-CaP) composites were developed by powder metallurgy method, using silica (SiO2) and anhydrous dicalcium phosphate (CaHPO4) powders (CaP) in the ratios (wt%): 20/80, 40/60, 60/40 and 80/20. The effects of temperature and chemical composition on crystallization and phase transformation of the SiO2-CaP composites were evaluated by XRD and FTIR. Thermal treatment of the starting material suggested that CaHPO4 transforms into: gamma-Ca2P2O7 at 800 degrees C; beta-Ca2P2O7 at 1000 degrees C and alpha-Ca2P2O7 at 1200 degrees C. On the other hand, beta-quartz was the only detected phase after thermal treatment of silica in the temperature range 800-1200 degrees C. For all SiO2-CaP composites, SiO2 and CaP did not modify the crystallization behavior of each other when sintered in the temperature range 800-1000 degrees C. However, at 1200 degrees C, CaP promoted the transformation of gamma-quartz into alpha-cristobalite. Moreover, SiO2 stabilized beta-Ca2P2O7. The modifications in the crystallization behavior were related to ion substitution and formation of solid solutions.

Bone Substitutes↗

PubMed2001

Effect of thermal treatment on bioactive glass microstructure, corrosion behavior, zeta potential, and protein adsorption.

Bioactive glass ceramic is characterized by high mechanical strength and a slow rate of bone bonding. To understand the factors contributing to a decrease in the rate of bone bonding to bioactive glass ceramic, we evaluated the effect of different percentages of bioactive glass crystallization on corrosion behavior, zeta potential, and serum protein adsorption. X-ray diffraction analysis showed that heat treatment of bioactive glass in the temperature range 550 degrees -700 degrees C resulted in the precipitation of Na(2)Ca(2)Si(3)O(9) crystals in the glass matrix. The percentage of crystallization increased in the order: 5%, 8%, 45%, and 83% after thermal treatment at 550 degrees, 600 degrees, 650 degrees, and 700 degrees C/1 h, respectively. Scanning electron microscopic analyses of bioactive glass treated at 550 degrees C showed major glass in glass-phase separation. Moreover, energy-dispersive X-ray analyses indicated that during crystallization P is concentrated in the glassy phase. Induced-coupled plasma analyses showed that after 24 h immersion in simulated body fluid, the concentration of the released P ion increased as the crystallization percentage of bioactive glass increased. zeta potential of bioactive glass samples containing 5% crystallization had a statistically significant higher negative value than control untreated bioactive glass (p <.02). Control untreated bioactive glass adsorbed a statistically significant higher amount of serum protein than bioactive glass samples containing 5% crystallization (p <.02). Results of our study suggest that inhibition of protein adsorption might be responsible for the slow rate of bone bonding to bioactive glass ceramic. It is also possible that conformation changes inhibit the activity of the protein adsorbed onto thermally treated bioactive glass.

Adsorption↗

PubMed1999

Effect of serum proteins on osteoblast adhesion to surface-modified bioactive glass and hydroxyapatite.

Previous studies indicate that modification of the surface of porous bioactive glass promotes osteoblast function. We hypothesize that bone formation on treated bioactive glass is due to the selective adsorption of serum attachment proteins. To test this hypothesis, we examined the profile of proteins adsorbed to treated bioactive glass and compared these proteins with those adsorbed to untreated bioactive glass and porous hydroxyapatite. Porous bioactive glass was treated with Tris-buffered electrolyte solution to generate a calcium phosphate-rich surface layer and then immersed in tissue-culture medium containing 10% serum. Proteins adsorbed to the ceramic surfaces were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analysis. Porous hydroxyapatite bound a higher amount of total protein than did the other substrates. However, surface-modified porous bioactive glass adsorbed more fibronectin than did hydroxyapatite. The effect of serum-protein adsorption on osteoblast adhesion to bioactive glass and hydroxyapatite was also evaluated. Cell adhesion to porous bioactive glass that was surface-modified and serum-treated was significantly greater than to porous bioactive glass that was either surface-modified or serum-treated. Furthermore, cell adhesion to porous bioactive glass treated to form the dual layer of calcium phosphate and serum protein was significantly higher than adhesion to porous hydroxyapatite with adsorbed serum protein. Results of the study strongly suggest that adsorption of serum fibronectin to the surface of modified porous bioactive glass coated with calcium phosphate may be responsible for enhanced osteoblast adhesion.

Absorption↗

PubMed1998

Laminin-5 coating enhances epithelial cell attachment, spreading, and hemidesmosome assembly on Ti-6A1-4V implant material in vitro.

Enhancement of epithelial cell attachment to laminin-5-coated titanium alloy (Ti-6Al-4V) implant material was evaluated in vitro. Protein analysis showed that Ti-6Al-4V has a high affinity for laminin-5 and adsorbed significantly more laminin-5 than laminin-1. DNA analysis showed that laminin-5 enhanced attachment of normal human epidermal keratinocytes (NHEK) to Ti-6Al-4V significantly more than did laminin-1 or uncoated controls. The effect of passivation on laminin-5 adsorption and activity on Ti-6Al-4V also was evaluated. Passivation had no significant effect on the amount of protein adsorbed; however, AFM, ESCA, and ToF-SIMS analyses suggested that passivation affects the conformation of adsorbed laminin-5. Although laminin-5 coating significantly enhanced rapid attachment of epithelial cells to both passivated and unpassivated Ti-6Al-4V, surface area measurements showed that cells spread on laminin-5-coated passivated Ti-6Al-4V covered a significantly larger surface area than cells spread on laminin-5-coated unpassivated samples. TEM analysis showed that cells formed significantly more hemidesmosomes on the surface of laminin-5 coated passivated than on the surface of laminin-5 coated unpassivated titanium alloy. The enhancement of rapid cell attachment, spreading, and hemidesmosome assembly on laminin-5-coated passivated samples may reflect better integration between epithelial cells and titanium alloy and thus may be predictive of long-term implant stability.

Cell Adhesion↗

PubMed1997

Porous bioactive glass and hydroxyapatite ceramic affect bone cell function in vitro along different time lines.

We describe the effects on cell function of treating porous bioactive glass (BG) such that its surface is a composite of carbonated hydroxyapatite and serum protein. The effects on bone cell function of porous hydroxyapatite (HA) ceramic and porous glass treated to become amorphous calcium phosphate only also were studied subsequent to their having adsorbed a serum protein layer. Substrates treated for different durations were seeded with MC3T3-E1 cells and cultured for 3-17 days. Whereas cells seeded on any substrates, BG and HA produced collagen types I and III, bone sialoprotein, and osteopontin, there were significant differences between HA and BG, and among the various surface conditions created on BG. Covering the glass surface with hydroxyapatite and serum protein enhanced expression of high alkaline phosphatase activity, high rates of cell proliferation, and production of mineralized extracellular matrix. The enhancement may be due to the adsorption of a high quantity of fibronectin from the serum onto the reacted bioactive glass surface.

Biocompatible Materials↗