Biomedical subjects

P Ducheyne

Publications and source records attributed to P Ducheyne.

At least 19 recordsLinked to original sources

PubMed1998

Quasi-biological apatite film induced by titanium in a simulated body fluid.

Commercially pure titanium (c.p.Ti) is capable of inducing the formation of a carbonated apatite onto its surface in a simulated body fluid (SBF) comprised of calcium ions, phosphate ions, and other inorganic species present in the body fluid. In addition to the incorporation of carbonate ions, such formed apatite has other important characteristics of the bone mineral phase, such as a small crystal size and ionic substitution by Mg2+ and Cl-. Thus, we call this apatite a quasi-biological apatite. The formation of the quasi-biological apatite is proposed to be related to TiOH groups that develop on the titanium surface through interaction with the SBF. The results suggest that titanium implants may be activated such that they can form a strong bond with bone tissue through the in vivo formation of apatite. Since the solution can reach any open space, the process discussed in this study is very suitable for coating porous titanium implants with a quasi-biological apatite film.

Apatites↗

PubMed1998

Bioactive glass fiber/polymeric composites bond to bone tissue.

Bioactive glass fibers were investigated for use as a fixation vehicle between a low modulus, polymeric composite and bone tissue. In an initial pilot study, bioactive glass fiber/polysulfone composites and all-polysulfone control rods were implanted into the rabbit tibia; the study was subsequently expanded with implantation into the rabbit femur. Bone tissue exhibited direct contact with the glass fibers and adjacent polymer matrix and displayed a mechanical bond between the composite and bone tissue after six weeks implantation. Interfacial bond strengths after six weeks implantation averaged 12.4 MPa, significantly higher than those of the all-polymer controls. Failure sites for the composite at six weeks generally occurred in the bone tissue or composite, whereas the failure site for the polymer implants occurred exclusively at the implant/tissue interface. The bioactive glass fiber/polysulfone composite achieved fixation to bone tissue through a triple mechanism: a bond to the bioactive glass fiber, mechanical interlocking between the tissue and glass fibers, and close apposition and possible chemical bond between the portions of the polymer and bone tissue. This last mechanism resulted from an overspill of bioactivity reactions from the fibers onto the surface of the surrounding polymer which we call the "halo" effect.

Animals↗

PubMed1998

Effect of serum proteins and osteoblasts on the surface transformation of a calcium phosphate coating: a physicochemical and ultrastructural study.

Changes occurring at the surface of a calcium phosphate coating when in contact with osteoblasts versus those in acellular solutions were analyzed. The coating studied is one with a well-documented extensive effect on short-term bone growth stimulation. Precipitates associated with original crystals and organized in a weblike structure were observed after a 3-week culture with osteoblasts. The precipitates were identified as carbonated hydroxyapatite (c-HA). In contrast, no significant surface changes were detected after immersion in an acellular serum-containing solution. However, in an acellular serum-free solution simulating the ionic composition of plasma, precipitates, identified as c-HA, were abundantly formed. Dissolution of the original coating preceded precipitation. The data support the hypothesis that dissolution of synthetic calcium phosphate ceramics is an initial step in their transformation to a biologically equivalent apatite, and suggest that both solution-mediated (dissolution-precipitation) and cell-mediated mechanisms are involved in the surface transformation.

Animals↗

PubMed1998

Effect of surface reaction stage on fibronectin-mediated adhesion of osteoblast-like cells to bioactive glass.

Bioactive glasses and ceramics enhance bone formation and bond directly to bone, and have emerged as promising substrates for bone tissue engineering applications. Bone bioactivity involves physicochemical surface reactions and cellular events, including cell attachment to adsorbed extracellular matrix proteins. The effects of fibronectin (Fn) adsorption and glass surface reaction stage on the attachment of osteoblast-like cells (ROS 17/2.8) to bioactive glass were analyzed. Bioactive glass disks were pretreated in a simulated physiologic solution to produce three reaction layers: unreacted glass (BG0), amorphous calcium phosphate (BG1d), and carbonated hydroxyapatite (BG7d). Synthetic hydroxyapatite (sHA) and nonreactive borosilicate glass (CG) were used as controls. A spinning disk device which applied a linear range of forces to attached cells while maintaining uniform chemical conditions at the interface was used to quantify cell adhesion. The number of adherent cells decreased in a sigmoidal fashion with applied force, and the resulting detachment profile provided measurements of adhesion strength. For the same amount of adsorbed Fn, cell adhesion was higher on surface-reacted bioactive glasses (BG1d and BG7d) than on BG0, CG, and sHA. For all substrates, cell attachment was primarily mediated by the RGD binding site of Fn, as demonstrated by blocking experiments with antibodies and RGD peptides. Cell adhesion strength increased linearly with adsorbed Fn surface density. Analysis of this fundamental relationship revealed that improved adhesion to reacted bioactive glasses resulted from enhanced cell receptor-Fn interactions, suggesting substrate-dependent conformational changes in the adsorbed Fn.

Biocompatible Materials↗

PubMed1998

Si-Ca-P xerogels and bone morphogenetic protein act synergistically on rat stromal marrow cell differentiation in vitro.

This study describes a novel bioactive xerogel glass as a carrier for bone morphogenetic protein (BMP) and the value of this carrier in terms of stimulating osteogenic activity of rat stromal marrow cells in vitro. These cells were seeded onto the surface of xerogel glass disks with BMP either incorporated in the glass, adsorbed to the surface of the glass, or added to the culture media and then compared to cells on glass with no added BMP or to cells on tissue culture plastic (TCP) with and without BMP. Cells were cultured for 6 and 10 days and examined for total DNA, alkaline phosphatase activity, and osteocalcin and total protein production. Stromal cell differentiation, as measured by alkaline phosphatase activity and osteocalcin synthesis was most increased when the BMP was incorporated or adsorbed onto the xerogel glass. Cells on xerogel glass without BMP were more differentiated than cells grown on plastic with BMP, thereby demonstrating the additive effect of a bioactive substrate and BMP on osteoblastic cell differentiation. These data indicate that xerogel glass effects differentiation of cells with osteogenic potential and that it can serve as a delivery vehicle for BMP.

Alkaline Phosphatase↗

PubMed1998

Flow intrusion characteristics and fracture properties of titanium-fibre-reinforced bone cement.

Two clinically relevant considerations for a new bone cement are its fracture properties and flow intrusion characteristics. We present data for a titanium-fibre-reinforced poly(methyl methacrylate) (Ti-PMMA). The fracture properties presented are a concise review of previously published material, while the flow intrusion observations are new. We performed fracture toughness and fatigue fracture experiments. Two types of fatigue specimens were designed and tested. A 'smooth' specimen represented the extreme case of minimum surface flaws. The lifetime of a 'smooth' specimen incorporates fatigue crack initiation (FCI) and fatigue crack propagation (FCP). 'Notched' specimens were created by machining a sharp notch into cylindrical specimens. The sharp notch effectively eliminated FCI from a random surface flaw and thus we made the assumption that the lifetime of the notched specimen was a function of FCP only. Fatigue testing was performed on rotating-bending fatigue machines until failure. Fibre addition resulted in a significant increase in fracture toughness over the control bone cement. Fibre addition and the combination of fibre addition and centrifugation increased the fatigue crack initiation and propagation resistance of the bone cement. For the intrusion studies, eight femurs were obtained from four dogs. The femurs were prepared following a procedure similar to that in human hip replacement surgery. One of the pair of femurs from each dog was filled with non-reinforced bone cement and the other was filled with Ti-PMMA. A stainless-steel rod was inserted into the cement to simulate the insertion of a prosthesis stem. The cemented bones were sectioned and then stained with Alizarin Red S to distinguish the bone from the PMMA or Ti-PMMA. Because of the irregular bone morphology, it was not practical to quantify intrusion depth, but instead to make general observations on the intrusion characteristics. The Ti fibres did not generally flow into the small openings; however, fibre addition did not hinder the bone cement's ability to penetrate into bone interstices.

Animals↗

PubMed1997

The effect of in vitro modeling conditions on the surface reactions of bioactive glass.

Using one parametric variation in solution composition, this paper documents that the surface reactions on bioactive glass (BG) 45S5 are exquisitely dependent upon the modeling conditions. The solutions used were 0.05 M tris hydroxymethyl aminomethane/HCl (tris buffer), tris buffer complemented with plasma electrolyte and/or serum, and serum. The reacted surfaces were analyzed using Fourier transform infrared (FTIR), scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDXA), and Rutherford backscattering spectroscopy (RBS). Post-immersion solutions were analyzed for changes in Ca and PO4 concentrations. After a short immersion (3 h), a crystalline, carbonated hydroxyapatite (c-HA) layer formed only in tris. Reaction surfaces of different structure, morphology, and composition were observed after various short and longer term immersions in all other solutions. They comprised two layers with the layer in contact with the bulk consisting mainly of Si; the outer layer, composed of Si, Ca, and P, was amorphous, and had a Ca/P ratio of about 1. Serum proteins adsorbed on the BG surfaces at the early stages of the solution-mediated BG reactions. Formation of a crystalline c-HA layer was delayed up to three or more days in solution with plasma ions. In the presence of serum, only amorphous surfaces composed of Si, Ca, and P were observed for any time up to seven days of immersion. The present data suggest that serum proteins adsorb in tandem with the occurrence of solution-mediated reactions leading to formation of a silica-gel. Amorphous Ca-P phases accumulate in the Si-rich matrix. Furthermore, the present data, in conjunction with the data published before, suggest that physicochemical and cell-mediated reactions occur in parallel to form the glass-tissue interfacial layer.

Biocompatible Materials↗

PubMed1997

Surface reaction layer formation in vitro on a bioactive glass fiber/polymeric composite.

In order to provide a fixation vehicle between a polymeric composite femoral hip prosthesis and bone tissue, we fabricated bioactive glass fibers. The glass fibers had a tensile strength of 596 MPa, 14 times that of bulk bioactive glass. After immersion in protein-free simulated body fluid for 10 days, we observed the development of a calcium phosphate layer (specifically, partially crystallized, calcium-deficient carbonated hydroxyapatite) on the surface of the glass fibers. The stages of the surface reaction layer formation were similar to those of 45S5 bioactive glass although the kinetics of the reaction layer formation were slower. We combined the bioactive glass fibers with a polymeric matrix to form a fiber-reinforced composite material and observed the formation of a calcium phosphate layer on the surface of the glass fibers within the composite material after immersion in both protein-free and protein-containing simulated body fluids. The rate of reaction layer formation was reduced in the presence of proteins. In both protein-free and protein-containing solutions, a "halo" of bioactivity reactions was observed on the surface of the polymer in regions surrounding the glass fibers. Our results suggest these glass fibers and glass fiber composites will exhibit bioactivity reactions in vivo.

Biocompatible Materials↗

PubMed1997

A comparison of the inflammatory potential of particulates derived from two composite materials.

In order to develop total joint prostheses with moduli of elasticity close to bone while retaining excellent strength characteristics, composite materials are being developed. Composites consist of graphite fibers embedded in a polymer matrix. We studied the inflammatory potential of particulates derived from two composites with different matrix components, polysulfone (PFS) and polyetherketoneketone (PEKK), in the rat subcutaneous air pouch model. Neat components of the composites were studied separately in the air pouch. Particulates also were studied in culture using the macrophage cell line RAW 264.7, adherent synovial cells (ASC), and human polymorphonuclear neutrophils (PMNs). Particles derived from the PEKK-containing composite material consistently were less inflammatory than the PFS composite-derived particles, as measured by PMN infiltration, neutral metalloprotease activity, tumor necrosis factor (TNF) activity, and prostaglandin E2 (PGE2) accumulation. Results from the neat materials confirmed the findings in the composite-derived material. PEKK composite-derived material produced less TNF from macrophage cultures, but there were no significant differences noted in PGE2 production from ASC or in superoxide anion generation from PMNs. Particles from both PSF and PEKK produced minimal inflammatory responses in the rat subcutaneous air pouch. PEKK elicited a response virtually the same as the saline control and significantly less than that produced by particles of PSF.

Animals↗

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↗

PubMed1997

Formation of surface reaction products on bioactive glass and their effects on the expression of the osteoblastic phenotype and the deposition of mineralized extracellular matrix.

The objective of the study was to examine the effect of alkali ion release, pH control and buffer capacity on the expression of the osteoblastic phenotype. In addition we determined the importance of modifications of the surface of porous bioactive glass (BG) on the activity of rat calvaria osteoblasts in vitro. We found that at a low tissue culture medium (TCM) volume to BG surface area (Vol/SA) ratio, the products of glass corrosion elevated the pH of the TCM to a value that adversely affected cellular activity; thus, the matrix synthesized by the cells was non-mineralized. On the other hand, when the Vol/SA was high and the buffer capacity of the medium was not exceeded, the cells generated a mineralized extracellular matrix. Addressing the second issue, we observed that modification of the composition of the BG surface markedly influenced osteoblast activity. BG that was coated with either a calcium phosphate-rich layer only or a serum protein layer changed the phenotypic characteristics of the osteoblasts. The presence of either of these surfaces lowered the alkaline phosphatase activity of the attached cells; this finding indicated that the osteoblast phenotype was not conserved. However, when the BG was coated with a bilayer of calcium phosphate and serum proteins, the alkaline phosphatase (AP) activity was elevated and the extracellular matrix contained characteristic bone markers. Our findings indicate that the calcium phosphate-rich layer promotes adsorption and concentration of proteins from the TCM, and it is utilized by the osteoblasts to form the mineralized extracellular matrix.

Adsorption↗

PubMed1997

Bone tissue reactions to an electrophoretically applied calcium phosphate coating.

Oral implants of a threaded design, calcium phosphate (CaP)-coated using an electrophoretic deposition technique, were compared to uncoated commercially pure (c.p.) titanium control in an animal study with 4 weeks and 6 months of follow-up, respectively. The 3D surface roughness of a CaP-coated implant was about three times greater than that of an uncoated control. Histomorphometric analyses of the direct bone-implant contact demonstrated a short-term advantage to the CaP-coated implants, whereas no significant difference to the uncoated titanium was found after 6 months. Comparison of the amount of bone inside or outside the threads showed similar values for test and control after 4 weeks. Significantly higher amounts of bone outside the uncoated c.p. titanium implants were measured after the long-term follow-up.

Animals↗

PubMed1997

Calcium phosphate ceramic coatings as carriers of vancomycin.

Infection in the setting of total joint arthroplasty remains a challenging problem. Attention has turned to developing methods of local delivery of antibiotics for prophylaxis. Vancomycin loaded into calcium phosphate ceramic coatings on titanium alloy substrates is a clinically relevant concept in the setting of total joint arthroplasty. Drug loading was accomplished by immersion of ceramic-coated discs in vancomycin-containing simulated physiological solution; in some experiments drug loading by immersion was followed by lipid coating in egg phosphatidylcholine solutions. The kinetics of vancomycin release and the efficacy of drug inhibition of Staphylococcus aureus were determined in vitro in comparison to the release from currently used antibiotic-laden poly(methyl methacrylate) (PMMA). The loading by immersion provided effective release and inhibition at early time points (up to 24 h); however, the lipid-coated samples demonstrated significant release and effective bacterial inhibition up to 72 h. The two-step procedure, i.e. drug loading followed by lipid coating in order to slow antibiotic elution, is more effective than the conventional one-step loading. The study indicated that the osteoconductive calcium phosphate coatings have the potential to serve as drug carriers to prevent infection in the setting of total joint arthroplasty.

Alloys↗

PubMed1997

In vitro release kinetics of biologically active transforming growth factor-beta 1 from a novel porous glass carrier.

Sol-gel silica-based porous glass (xerogel) was used as a novel carrier material for recombinant human transforming growth factor-beta 1 (TGF-beta 1). Room temperature synthesis procedures included sol preparation, the addition of TGF-beta 1 solution to the sol, subsequent gelation and drying. After determination of optimal synthesis parameters, the material was assayed in vitro for its ability to release biologically active TGF-beta 1 in a controlled manner. Sustained release of TGF-beta 1 over a 7-day period was demonstrated. On the basis of published TGF-beta 1 potency, the amount released is capable of eliciting bone tissue reactivity. These findings suggest that this novel glass-growth factor composite may serve as an effective bone graft material for the repair of osseous defects.

Biocompatible Materials↗

PubMed1997

Quantification of cell adhesion using a spinning disc device and application to surface-reactive materials.

Quantitative analysis of cell adhesion is essential in understanding physiological phenomena and developing biotechnological applications. Electrochemical measurements demonstrated that the transport patterns associated with a spinning disc device approximate the fluid flow and mass transport fields for a disc spinning in an infinite fluid. Therefore, this device applies a linear range of forces to attached cells under uniform and constant chemical conditions at the interface. The application of this apparatus for examining cell adhesion to surface-active materials was illustrated by investigating the attachment of osteoblast-like cells to fibronectin adsorbed onto bioactive and non-reactive glasses for different chemical environments. Cells were seeded on fibronectin-coated substrates for 15 min and then subjected to detachment forces for 10 min. The number of adherent cells decreased non-linearly with applied force and the detachment profile was accurately described by a sigmoidal curve fit, as expected for a cell population with normally distributed adhesion properties.

Adsorption↗

PubMed1997

Orderly oriented wire mesh: a novel porous coating.

As an alternative to commercially available porous beads and fiber metal mesh, a new porous coating, orderly oriented wire mesh (OOWM), was developed. Rectangular plugs, 10 x 5 x 5 mm with porous-coated beads, and four different OOWM configurations were inserted into bilateral femoral condyles of adult beagles. Dogs were sacrificed immediately after implantation, and at 4 weeks, 8 weeks, and 12 weeks postimplantation. Mechanical pullout strength of plugs revealed that porous beads are equivalent to the simplest OOWM at 12 weeks postimplantation. Of the four OOWMs tested, the 25 x 25 single layer was significantly more stable than others at 4 weeks postimplantation. These results indicate that in an in vivo unloaded model, OOWM is just as effective as the porous beads in achieving early bone ingrowth and stability.

Animals↗

PubMed1997

Bioactive glass particles of narrow size range for the treatment of oral bone defects: a 1-24 month experiment with several materials and particle sizes and size ranges.

The aim of this study was to evaluate bone growth around bioactive glass particles in bone defects in comparison to hydroxylapatite particles. The bioactive glass particles were implanted in the partial edentulous jaws of Beagle dogs in two different compositions and several sizes and size ranges. After 1, 2, 3, 6, 12 and 24 months the samples were harvested and processed for undecalcified sectioning. Histological analysis showed a superior response of the bioactive glass particles of composition A and narrow size range (300-355 microns). Besides extensive osteoconductive properties, the bone repair was also stimulated by bone growth in the internally eroded particles. The data demonstrate conclusively that the well known corrosion reactions of the bioactive glass lead to the formation of protective pouches. In these protective pouches formation of new bone is detected without this bone being connected to the bone tissue outside the particles. These islands of newly formed bone tissue function as nuclei for further bone growth and enhance the repair of the defect.

Animals↗

PubMed1996

Effect of serum proteins on solution-induced surface transformations of bioactive ceramics.

The kinetics of immersion-induced surface transformation reactions of synthetic bone bioactive ceramics were studied in vitro in either protein-free or protein-containing simulated physiological solutions. Both solutions had an ion content similar to that of plasma. Synthetic ceramics used for the study included Ca-deficient hydroxyapatite (CDHA), stoichiometric HA either not well crystallized or well crystallized (s-HA nwc or s-HA wc), oxyhydroxyapatite (OHA), beta-tricalcium phosphate (beta-TCP), and porous coralline HA (I-HA) and calcium carbonate (CC). Only CDHA and nwc s-HA led to immediate precipitation in both protein-free and protein-containing solutions. In contrast, reactions of wc HA and I-HA showed lag times to onset of precipitation in the protein-free solution and a further delay in the presence of proteins. The reactions of nonapatitic ceramics whose lag times in the protein-free solution were longer than those of apatitic, were completely blocked in the presence of proteins within the duration of the experiment (up to 3 days). CDHA and nwc s-HA were the only ceramics that, in the presence of serum proteins, led to the formation of B-type carbonated apatite, typical for calcified tissue apatite.

Animals↗