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Klaas de Groot

Publications and source records attributed to Klaas de Groot.

12 recordsLinked to original sources
PubMed2006

Osteoinduction by biomaterials--physicochemical and structural influences.

Osteoinduction by biomaterials has been shown to be a real phenomenon by many investigators in the last decade. The exact mechanism of this phenomenon is, however, still largely unknown. This in vivo study in goats was performed to get insight into processes governing the phenomenon of osteoinduction by biomaterials and had four main goals: (i) to further investigate the influence of physicochemical properties and structure on biomaterial osteoinductive potential, (ii) to investigate the influence of implant size on the amount of induced bone, (iii) to investigate implantation site dependence, and (iv) to investigate changes occurring on the surface of the material after implantation. Intramuscular implantations of four different biphasic calcium phosphate ceramics, consisting of hydroxyapatite and beta-tricalcium phosphate and a carbonated apatite ceramic, indicated that, for a maximal osteoinductive potential, there is an optimal specific surface area for each material type. It was further shown that a decrease of the implant size with a half significantly decreased the relative amount of induced bone. In addition, subcutaneous implantation did not give rise to ectopic bone formation in any of the animals, while bone was induced in most animals intramuscularly. Analysis of the surfaces of the materials after subcutaneous implantation inside diffusion chambers indicated that the increased specific surface area leads to more surface reactivity, which is hypothesized to be essential for osteoinductivity by biomaterials.

Animals↗
PubMed2006

Electrolytic deposition of calcium phosphate/chitosan coating on titanium alloy: growth kinetics and influence of current density, acetic acid, and chitosan.

Electrolytically deposited calcium phosphate/chitosan coating demonstrated good bone marrow stromal cell attachment. The aim of this study was to understand the coating's growth kinetics as well as the effects of current density, acetic acid, and chitosan on the coating's formation. The scanning electron micrographs found that calcium phosphate crystals homogeneously distributed into chitosan aggregates as early as 30 min. X-ray diffraction patterns and Fourier transform infrared spectra demonstrated that the coating experienced a compositional conversion from octacalcium phosphate to carbonate apatite during the deposition process. Electric current influenced the deposition. Higher current density accelerated the process and induced faster and more chitosan deposition. Both acetic acid and chitosan were found to inhibit calcium phosphate deposition. Chitosan was thought to induce stronger effects than acetic acid did. Furthermore, the inhibitive effect related to their concentration in the electrolyte. When chitosan concentration increased to a certain degree, this inhibitive effect not only affected calcium phosphate deposition, but also affected its own deposition. The chitosan content within the hybrid coating was small, which could be verified through Raman spectrum. At the same time, no clear evidence of chemical reactions could be found between these two components. We considered that both components were just naturally wrapped to form as a whole.

Alloys↗
PubMed2006

Relevance of osteoinductive biomaterials in critical-sized orthotopic defect.

Several publications have shown the phenomenon of osteoinduction by biomaterials to be real. However, whether the ability of a biomaterial to initiate bone formation in ectopic implantation sites improves the performance of such osteoinductive biomaterial in clinically relevant orthotopic sites remains unclear. No studies have been published in which osteoinductive potential of a biomaterial is directly related to its performance orthotopically. In this study, we compared osteoinductive and nonosteoinductive biphasic calcium-phosphate (BCP) ceramics ectopically and in a clinically relevant critical-sized orthotopic defect in goats. The two materials, BCP1150 and BCP1300, had similar chemical compositions, crystallinities, and macrostructures, but their microstructures differed significantly. BCP1150, sintered at a lower temperature, had a large amount of micropores, small average crystal size, and hence a high specific surface area. In contrast, BCP1300, with few micropores, had a significantly lower specific surface area as compared to BCP1150. Twelve-week intramuscular implantation in goats (n = 10) showed that bone was induced in all BCP1150 implants, while no signs of bone formation were found in any of the BCP1300 implants. After 12 weeks of implantation in a bilateral critical-sized iliac wing defect in the same goats, BCP1150 showed significantly more bone than BCP1300. In addition, the analysis of fluorochrome markers, which were administered to the animals 4, 6, and 8 weeks after implantation to follow the bone growth dynamics, showed an earlier start of bone formation in BCP1150 as compared to BCP1300. Significantly better performance of an osteoinductive ceramic in a critical-sized orthotopic defect in a large animal model in comparison to a nonosteoinductive ceramic suggests osteoinduction to be clinically relevant. Further improvement of material osteoinductive properties is thus a significant step forward in the search for alternatives for autologous bone graft.

Animals↗
PubMed2006

Cross-species comparison of ectopic bone formation in biphasic calcium phosphate (BCP) and hydroxyapatite (HA) scaffolds.

Material-induced bone formation reported in canine, bovid, suid, and primate species does not often occur in lagomorph or rodent models. In this study, we test biphasic calcium phosphate and hydroxyapatite- induced bone formation in subcutaneous pockets of mice and intramuscular pockets in rats, rabbits, and dogs. All scaffolds are of similar size, and all animals were sacrificed at 90 days post-implantation. In dogs (N = 8), all implants showed bone formation with significantly more bone formed in biphasic calcium phosphates (30 +/- 6%, N = 8) as compared to hydroxyapatite (14 +/- 5%, N = 8) (p = 0.003). Hydroxyapatite implants did not induce bone formation in mice, rats, or rabbits. Biphasic calcium phosphate induced bone in 6 of 8 scaffolds implanted in 4 rabbits and 3 of 16 scaffolds implanted in 16 mice, whereas it did not induce bone formation in any of the 8 rats. The results presented herein suggest that the incidence of material-induced bone formation varies with animal species and is related to the implant material used.

Animals↗
PubMed2005

Porous Ti6Al4V scaffold directly fabricating by rapid prototyping: preparation and in vitro experiment.

Three-dimensional (3D) fiber deposition (3DF), a rapid prototyping technology, was successfully directly applied to produce novel 3D porous Ti6Al4V scaffolds with fully interconnected porous networks and highly controllable porosity and pore size. A key feature of this technology is the 3D computer-controlled fiber depositing of Ti6Al4V slurry at room temperature to produce a scaffold, consisting of layers of directionally aligned Ti6Al4V fibers. In this study, the Ti6Al4V slurry was developed for the 3D fiber depositing process, and the parameters of 3D fiber depositing were optimized. The experimental results show how the parameters influence the structure of porous scaffold. The potential of this rapid prototyping 3DF system for fabricating 3D Ti6Al4V scaffolds with regular and reproducible architecture meeting the requirements of tissue engineering and orthopedic implants is demonstrated.

3T3 Cells↗
PubMed2005

Biological performance of uncoated and octacalcium phosphate-coated Ti6Al4V.

The in vivo behavior of a porous Ti6Al4V material that was produced by a positive replica technique, with and without an octacalcium phosphate (OCP) coating, has been studied both in the back muscle and femur of goats. Macro- and microporous biphasic calcium phosphate (BCP) ceramic, known to be both osteoconductive and able to induce ectopic bone formation, was used for comparison purpose. The three groups of materials (Ti6Al4V, OCP Ti6Al4V and BCP) were implanted transcortically and intramuscularly for 6 and 12 weeks in 10 adult Dutch milk goats in order to study their osteointegration and osteoinductive potential. In femoral defects, both OCP Ti6Al4V and BCP were performing better than the uncoated Ti6Al4V, at both time points. BCP showed a higher bone amount than OCP Ti6Al4V after 6 weeks of implantation, while after 12 weeks, this difference was no longer significant. Ectopic bone formation was found in both OCP Ti6Al4V and BCP implants after 6 and 12 weeks. The quantity of ectopically formed bone was limited as was the amount of animals in which the bone was observed. Ectopic bone formation was not found in uncoated titanium alloy implants, suggesting that the presence of calcium phosphate (CaP) is important for bone induction. This study showed that CaPs in the form of coating on metal implants or in the form of bulk ceramic have a significantly positive effect on the bone healing process.

Alloys↗
PubMed2005

3D microenvironment as essential element for osteoinduction by biomaterials.

In order to unravel the mechanism of osteoinduction by biomaterials, in this study we investigated the influence of the specific surface area on osteoinductive properties of two types of calcium phosphate ceramics. Different surface areas of the ceramics were obtained by varying their sintering temperatures. Hydroxyapatite (HA) ceramic was sintered at 1150 and 1250 degrees C. Biphasic calcium phosphate (BCP) ceramic, consisting of HA and beta-tricalcium phosphate (beta-TCP), was sintered at 1100, 1150 and 1200 degrees C. Changes in sintering temperature did not influence the chemistry of the ceramics; HA remained pure after sintering at different temperatures and the weight ratio of HA and beta-TCP in the BCP was independent of the temperature as well. Similarly, macroporosity of the ceramics was unaffected by the changes of the sintering temperature. However, microporosity (pore diameter <10 microm) significantly decreased with increasing sintering temperature. In addition to the decrease of the microporosity, the crystal size increased with increasing sintering temperature. These two effects resulted in a significant decrease of the specific surface area of the ceramics with increasing sintering temperatures. Samples of HA1150, HA1250, BCP1100, BCP1150 and BCP1200 were implanted in the back muscles of Dutch milk goats and harvested at 6 and 12 weeks post implantation. After explantation, histomorphometrical analysis was performed on all implants. All implanted materials except HA1250 induced bone. However, large variations in the amounts of induced bone were observed between different materials and between individual animals. Histomorphometrical results showed that the presence of micropores within macropore walls is necessary to make a material osteoinductive. We postulate that introduction of microporosity within macropores, and consequent increase of the specific surface area, affects the interface dynamics of the ceramic in such a way that relevant cells are triggered to differentiate into the osteogenic lineage.

Animals↗
PubMed2004

Nano-scale study of the nucleation and growth of calcium phosphate coating on titanium implants.

The nucleation and growth of a calcium phosphate (Ca-P) coating deposited on titanium implants from simulated body fluid was investigated by using atomic force microscopy (AFM) and environmental scanning electron microscopy (ESEM). Forty titanium alloy plates were assigned into two groups. One group with a smooth surface having a maximum roughness R(max) < 0.10 microm (s-Ti6Al4V) and a group with a rough surface with an R(max) < 0.25 microm (r-Ti6Al4V) were used. Titanium samples were immersed in SBF concentrated by five (SBF x 5) from 10 min to 5 h and examined by AFM and ESEM. Scattered Ca-P deposits of approximately 15 nm in diameter appeared after only 10 min of immersion in SBF x 5. These Ca-P deposits grew up to 60-100 nm after 4 h on both s- and r-Ti6Al4V substrates. With increasing immersion time, the packing of Ca-P deposits with size of tens of nanometers in diameter formed larger globules and then a continuous Ca-P film on titanium substrates. A direct contact between the Ca-P coating and the Ti6Al4V surface was observed. The Ca-P coating was composed of nanosized deposits and of an interfacial glassy matrix. This interfacial glassy matrix might ensure the adhesion between the Ca-P coating and the Ti6Al4V substrate. In the case of s-Ti6Al4V substrate, failures within this interfacial glassy matrix were observed overtime. Part of the glassy matrix remained on s-Ti6Al4V while part detached with the Ca-P film. The Ca-P coating detached from the smooth substrate, whereas the Ca-P film extended onto the whole rough titanium surface over time. In the case of r-Ti6Al4V, the Ca-P coating covered evenly the substrate after immersion in SBF x 5 for 5 h. The present study suggested that the heterogeneous nucleation of Ca-P on titanium was immediate and did not depend on the Ti6Al4V surface topography. The further growth and mechanical attachment of the final Ca-P coating strongly depended on the surface, for which a rough topography was beneficial.

Alloys↗
PubMed2003

Osteogenecity of octacalcium phosphate coatings applied on porous metal implants.

The biomimetic route allows the homogeneous deposition of calcium phosphate (Ca-P) coatings on porous implants by immersion in simulated physiologic solution. In addition, various Ca-P phases, such as octacalcium phosphate (OCP) or bone-like carbonated apatite (BCA), which are stable only at low temperatures, can be deposited. In this pilot study, experiments were designed with a twofold-purpose: (1) to investigate the osteoinduction of OCP-coated and noncoated porous tantalum cylinders and of dense titanium alloy cylinders (5 mm in diameter and 10 mm in length) in the back muscle of goats at 12 and 24 weeks (n = 4); and (2) to compare the osteogenic potentials of BCA-coated, OCP-coated, and bare porous tantalum cylinders in a gap of 1 mm created in the femoral condyle of a goat at 12 weeks (n = 2). In the goat muscle, after 12 weeks the OCP-coated porous cylinder had induced ectopic bone as well as bone within the cavity of the OCP-coated dense titanium cylinder. In the femoral condyle, bone did not fill the gap in any of the porous implants. In contrast with the two other groups, OCP-coated porous cylinders exhibited bone formation in the center of the implant. The nature of the Ca-P coating, via its microstructure, its dissolution rate, and its specific interactions with body fluids, may influence the osteogenecity of the Ca-P biomaterial.

Animals↗
PubMed2003

Screening molluscan cDNA expression libraries with anti-shell matrix antibodies.

In a previous paper [Marin et al., Protein Expr. Purif. 23 (2001) 175], we showed that polyclonal antibodies raised against molluscan shell matrices could be useful tools for visualizing shell proteins after a preparative fractionation of the shell matrix. In this paper, we have used the same antibodies for screening a cDNA library constructed from mantle tissues of the nacro-prismatic bivalve Pinna nobilis. The immunoscreening led to the identification of a new protein, mucoperlin [Marin et al., J. Biol. Chem. 275 (2000) 20667], which was subsequently overexpressed. A polyclonal antibody was obtained from the recombinant mucoperlin. In a control assay, we unambiguously demonstrated that this antibody and one of the sera used for the initial screening hybridize with the same clones. We assess that screening cDNA libraries with antibodies elicited against unfractionated calcifying matrices is a good alternative to oligonucleotide screening techniques, particularly in the field of molluscan biomineralization where only few gene sequences are known.

Animals↗
PubMed2002

Synthesis of macroporous hydroxyapatite scaffolds for bone tissue engineering.

A novel method of preparing macroporous hydroxyapatite (HA) by dual-phase mixing was developed: HA slurry and Polymethylmethacrylate (PMMA) resin were mixed together at the volume ratio of 1:1. After pyrolytic removal of the PMMA phase, HA with an open porous structure was obtained. In this way, the porosity of the ceramic was limited to 50%. Attempts to increase the porosity by adding more PMMA resin were confronted with the technical hurdle of sample collapse during the pyrolysis process. To increase the porosity and to improve pore interconnection, an extra foaming step was introduced before the polymerization of PMMA resin. Three foaming agent systems were tried, based on the reactions of citric acid and (bi)carbonate salts: sodium bicarbonate, calcium carbonate, and ammonium bicarbonate. Although all the three foaming agents were able to increase the porosity up to 70%, keeping all the pores interconnected throughout, only ammonium bicarbonate system turned out to be applicable to make HA scaffolds or implants, because both NaHCO(3) and CaCO(3) systems caused alkalic residues in the final ceramic. The porous HA samples were fully characterized by FTIR, XRD, ESEM (EDX), and optical microscopy.

Bone and Bones↗