Papers by Author: Joop G.C. Wolke

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Authors: Joop G.C. Wolke, E. Vandenbulcke, B. van Oirschot, John A. Jansen
Abstract: The RF magnetron sputter technique was used to deposit Bioglass (BG) and hydroxyapatite (HA) coatings onto titanium substrates. In the current study, the physico-chemical and dissolution properties of various deposited coatings were investigated. X-ray diffraction demonstrated that the as-sputtered coatings had an amorphous structure, a heattreatment for 2 hours at 600°C changed only the HA coating into a crystalline apatite structure. Dissolution experiments demonstrated that all the amorphous coatings dissolved during the incubation for 4 weeks in simulated body fluid, while all the heattreated sputter coatings were still maintained. In contrast with the HA heattreated sputter coatings all the bioglass containing sputter coatings showed the formation of a crystalline apatite phase. Scanning electron microscopical examination of the sputtered coatings demonstrated that on all the heattreated BG/HG sputter coating a thick CaP precipitate was formed, while on the BG sputter coating occasionally a globular precipitate was observed.
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Authors: Edwin van der Wal, Arnoud W. Denier van der Gon, Siwart J. Oldenburg, Joop G.C. Wolke, John A. Jansen, Arjen M. Vredenberg
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Authors: John A. Jansen, Joop G.C. Wolke, E.M. Ooms
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Authors: R.P. Félix Lanao, J.W.M. Hoekstra, Joop G.C. Wolke, Sander C.G. Leeuwenburgh, A.S. Plachokova, O.C. Boerman, Jeroen J.J.P. van den Beucken, John A. Jansen
Abstract: Periodontitis is one of the most common inflammatory diseases, which can lead to early tooth loss. The conventional treatment of periodontitis is to arrest the disease progression. Most reconstructive procedures involve application of bone substitutes, barrier membranes or a combination of both into the bony defects. Calcium phosphate cements (CPCs) are the predominant type of bone substitute material used for reasons of injectability and hence perfect filling potential for bone defects. Recently, injectable apatitic CPCs demonstrated to be more rapidly degradable when combined with poly (lactic-co-glycolic) acid (PLGA) microspheres. Further, PLGA microspheres can be used as a delivery vehicle for growth factors. In this study, the performance of injectable CPCs as a bone substitute material for alveolar bone defects created in Beagle dogs was evaluated. Four CPC-formulations were generated by incorporating hollow or dense PLGA microspheres, either or not loaded with the growth factors (platelet derived growth factor (PDGF) and insulin-like growth factor (IGF). Implantation period was 8 weeks. Bone formation was based on histological and histomorphometrical evaluation. The results demonstrated that filling alveolar bone defects with CPC-dense PLGA revealed significant more bone formation compared to CPC-hollow PLGA either or not loaded with IGF and PDGF. In summary, we conclude that injectable CPC-dense PLGA composites proved to be the most suitable material for a potential use as off the shelf material due to its good biocompatibility, enhanced degradability and subsequent bone formation.
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Authors: Kemal Sariibrahimoglu, Joop G.C. Wolke, Sander C.G. Leeuwenburgh, John A. Jansen
Abstract: Calcium phosphate cements (CPCs) can be a suitable scaffold material for bone tissue engineering because of their osteoconductivity and perfect fit with the surrounding tissue when injected in situ. However, the main disadvantage of hydroxyapatite (HA) forming CPC is its slow degradation rate, which hinders complete bone regeneration. A new approach is to use hydraulic apatite cement with mainly α/β-tricalciumphosphate (TCP) instead of α-TCP. After hydrolysis the α/β-TCP transforms in a partially non-absorbable HA and a completely resorbable β-TCP phase. Therefore, α-TCP material was thermally treated at several temperatures and times resulting in different α/β-TCP ratios. In this experiment, we developed and evaluated injectable biphasic calcium phosphate cements (BCPC) in vitro. Biphasic α/β-TCP powder was produced by heating α-TCP ranging from 1000-11250°C. Setting time and compressive strength of the CPCs were analyzed after soaking in PBS for 6 weeks. Results demonstrated that the phase composition can be controlled by the sintering temperature. Heat treatment of α-TCP, resulted in 100%, 75% and 25% of α-to β-TCP transformation, respectively. Incorporation of these sintered BCP powder into the cement formulation increased the setting time of the CPC paste. Compressive strength decreased with increasing β-TCP content. In this study, biphasic CPCs were produced and characterized in vitro. This injectable biphasic CPC presented comparable properties to an apatitic CPC.
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Authors: Sander C.G. Leeuwenburgh, Joop G.C. Wolke, J. Schoonman, John A. Jansen
Abstract: The recently developed Electrostatic Spray Deposition (ESD) technique was used in order to deposit calcium phosphate (CaP) coatings onto various substrates, since this technique enables deposition of inorganic thin films with a variety of morphological and chemical properties. In the present study, the relationship between various deposition parameters and the physicochemical properties of deposited coatings was investigated in order to be able to deposit CaP coatings with defined chemical and morphological properties using ESD. The results showed that the chemical characteristics of the coatings were determined by both the composition of the precursor solutions (solution acidity, absolute and relative precursor concentrations) and apparatus-related parameters, such as the liquid flow rate and the nozzle-tosubstrate distance. By varying these parameters, several crystal phases and phase mixtures were obtained (carbonate apatite, carbonated hydroxyapatite, a/b-tricalciumphosphate, monetite, b/g-pyrophosphate, metaphosphate, calcite/calcium oxide). Coating morphology was also shown to be strongly dependent on several deposition parameters. A wide range of coating morphologies was obtained, varying from relatively dense to highly porous, reticular coating surface architectures.
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Authors: Sander C.G. Leeuwenburgh, M.C. Heine, Joop G.C. Wolke, Sotiris E. Pratsinis, J. Schoonman, John A. Jansen
Abstract: In situ measurements of electrospray droplet sizes and velocities were performed by Phase Doppler Anemometry during Electrostatic Spray Deposition (ESD) of calcium phosphate (CaP) coatings. Numerous processing parameters were varied (nozzle-to-substrate distance, deposition temperature, nozzle geometry, and composition of the precursor solution), whereafter the morphological characteristics of these ESD-derived CaP coatings were correlated with measured droplet characteristics. Equal droplet sizes and velocities were measured for nozzle-to-substrate distances up to 40 mm and deposition temperatures up to 400 °C, indicating that electrospray droplets did not shrink at all during droplet flight using an involatile solvent butyl carbitol with a high boiling point (Tb = 231 °C). Nevertheless, coatings with considerably different surface morphologies were obtained under these conditions, varying from microporous structures with coalesced pore walls to morphologies revealing isolated rings on top of dense or grainy underlayers. The chemical composition of the precursor solutions and the mixing characteristics of the calcium and phosphate precursor components strongly influenced the initial droplet sizes, precipitation kinetics of the CaP solute, and subsequent coating morphology. Unique, reticular coating morphologies were deposited at a deposition rate of 3.2 µm/hour, which have a graded structure consisting of a dense underlayer, a submicron-porous intermediate layer, and a roughened toplayer revealing droplet-derived features such as isolated rings or coalesced, hollow surface pits.
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Authors: Edwin van der Wal, Joop G.C. Wolke, John J. Jansen, Arjen M. Vredenberg
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Authors: Lise de Jonge, Jeroen J.J.P. van den Beucken, Sander C.G. Leeuwenburgh, Joop G.C. Wolke, John A. Jansen
Abstract: Protein thin films were prepared by electrostatic spray deposition (ESD) from aqueous solutions of the enzyme alkaline phosphatase (ALP). ALP thin films with preserved functional properties were successfully deposited using the ESD technique. The biological activity of the deposited ALP films was investigated in vitro by immersing the ESD-coated titanium substrates in both simulated body fluid (SBF) and cell-culture medium. Mineral deposition occurred on substrates immersed in both SBF and medium. Various analytical techniques (SEM,XRD,FTIR,EDS) showed that the calcium phosphate layers deposited in SBF and medium differ in both crystallinity and morphology. The results demonstrated that ESD is a successful method for the deposition of biomedical coatings with enhanced functionality.
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Authors: Joop G.C. Wolke, Jeroen J.J.P. van den Beucken, John A. Jansen
Abstract: The RF magnetron sputter technique was used to deposit Bioglass (BG) and hydroxyapatite (HA) coatings onto titanium substrates. The aim of this study was evaluated the growth behavior of rat bone marrow cells of various deposited coatings. The EDS measurements demonstrated that the composition BG coating was changed during magnetron sputtering. The rat bone marrow derived osteoblast-like cells showed improved osteogenic response on crystalline magnetron sputtered HA coatings compared BG coatings. Scanning electron microscopical examination showed an extensive mineralization after 16 days of culture, while on the surface of the BG coating only a multilayer without mineralization could be observed.
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