Papers by Author: Paul Ducheyne

Abstract: Although autogenous bone grafts are currently the standard of care for bone reconstruction in implant dentistry, bone substitute materials are extensively studied in order to avoid harvesting autogenous bone. Recently, the use of tricalcium phosphate (TCP) and bioactive glass 45S5 particles as alloplastic bone graft materials for alveolar ridge augmentation and sinus floor elevation procedures has received increasing attention in implant dentistry. However, given the clinical findings with these current bone substitute materials there continues to be interest in bone substitute materials which degrade more rapidly, but still stimulate osteogenesis at the same time. As a result considerable efforts have been undertaken to produce rapidly resorbable bone substitute materials, which exhibit good bone bonding behaviour by stimulating enhanced bone formation at the interface in combination with a high degradation rate. This has led to the synthesis of a new series of bioactive, rapidly resorbable calcium alkali phosphate materials. These are glassy crystalline calcium alkali orthophosphates, which exhibit stable crystalline Ca₂KNa(PO₄)₂ phases. These materials have a higher solubility than TCP and therefore they are designed to exhibit a higher degree of biodegradability than TCP. On this basis, they are considered as excellent alloplastic materials for alveolar ridge augmentation. In order to evaluate the osteogenic potential in vitro, we first examined the effect of various rapidly resorbable calcium alkali orthophosphate bone grafting materials on the expression of osteogenic markers characteristic of the osteoblastic phenotype in vitro and compared this behaviour to that of the currently clinically used materials β-tricalcium phosphate (TCP) and bioactive glass 45S5. These studies showed that several calcium alkali orthophosphate materials supported osteoblast differentiation to a greater extent than TCP.

Abstract: Controlled release silica sol-gels are room temperature processed, porous, resorbable, and biocompatible materials. Many molecules including drugs, proteins, and growth factors can be released from sol-gels, and the quantity and duration of the release can vary widely. Processing parameters render these release properties exquisitely versatile [1]. The synthesis of controlled release sol-gels involves several steps: an acid-catalyzed hydrolysis to form a sol with the molecules included, followed by casting, aging, and drying. Additional steps such as grinding and sieving are required to produce sol-gel granules of a desirable size. In this study, we focus on the synthesis of controlled release sol-gel microspheres by using a novel process, which involves only two steps:sol formation followed by emulsification. Sol-gel microspheres containing either vancomycin (antibiotic) or bupivacaine (analgesic) were successfully synthesized via this synthesis route. Both drugs showed controlled, load-dependent and time-dependent release from the microspheres. The in vitro release properties of sol-gel microspheres were different from those of sol-gel granules produced by grinding and sieving. In comparison to a fast, short-term release from the granules, the release from the microspheres was slower and of longer duration. In addition, the degradation rate of microspheres was significantly slower than that of the granules. These data enable the use of sol-gel powders for controlled long-term release.

Abstract: In this paper, the hydration product of calcium phosphate cement with bioactive glass containing Si was used to investigate the effect of chemical composition on its bioactivity. The variation of concentrations of Ca2+, P and Si in TE solution complemented with electrolytes typical for plasma (TEE) and the formation of amorphous calcium phosphate layer on the surface of the materials were investigated by immersing the designed materials in TEE solution in vitro. The results showed that the composition of the bioactive composite CPC greatly affected its behavior in the solution and the formation of bioactive apatite. After immersed in TEE solution, the Ca ions were uptaken for all the samples, showing the decreases of Ca concentration during the entire duration, but the concentration of P ions increased sharply at the initial stage, and then decreased due to the formation of amorphous calcium phosphate layer on the surface of the materials. FTIR revealed that the layer was poorly crystallized Ca-deficient carbonate apatite. The thickness of the layer was more than 12 um, which layer was composed of rod-like apatite with directional arrangement. All the data obtained would be useful for the design and optimization of the orthopedic degradable implant inorganic materials.

Abstract: Beneficial properties of room temperature processed silica sol-gels as resorbable and biocompatible materials for the controlled release of drugs and macromolecules have been described before. Recently, it was shown that a thin sol-gel film can be used for the controlled delivery of antibiotics such as vancomycin. It was also demonstrated that the release and degradation properties of the sol-gel films can be tailored via processing parameters. In this work, we evaluated the in vitro and in vivo bactericidal effects of vancomycin-containing thin sol-gel films applied on Ti-alloy intramedullary nails. Both the in vitro and the in vivo results demonstrate a pronounced bactericidal effect of the sol-gel/antibiotic films. This study suggests that thin antibiotic-containing sol-gel film holds great promise for the prevention and treatment of bone infections.

Abstract: Current tissue engineering strategies involve the use of scaffold materials with properties specific for the target tissue. When the tissue being treated is bone, properties such as bone bonding behaviour and excellent biological performance are very desirable. Many strategies involve the creation in vitro of a suitable hybrid construct (i.e., comprising a scaffold material and cells). These scaffolds are then inserted into the defect site, thus achieving faster integration and hence, repair. Herein, we describe the synthesis and characterization of starch-based microparticles for bone tissue engineering. This study describes the properties of two types of starch-based microparticles: their bioactivity in vitro (when processed with Bioactive Glass 45S5), the good biological performance and also the ability to be used as controlled release vehicles of bioactive molecules, such as steroids and growth factors.

Abstract: Previously, the properties of room temperature processed silica sol gel (also called xerogels) as resorbable and biocompatible controlled release systems were described. It was demonstrated that drugs and macromolecules with a variety of properties and characteristics could be released in a controlled manner. In this study, we focus on the synthesis of antibacterial thin solgel films on intramedullary nails and fracture fixation materials. We determine the effect of processing parameters on the in vitro properties and demonstrated a time- and load- dependent release of vancomycin from the film. This study suggests that thin sol-gel films hold great promise for the prevention and treatment of bone infections.

Abstract: A previous study demonstrated that the incorporation of bioactive glass (BG) into poly (lactic-co-glycolic acid) (PLGA) can promote the osteoblastic differentiation of marrow stromal cells (MSC) on PLGA by forming a calcium phosphate rich layer on its surface. To further understand the mechanisms underlying the osteogenic effect of PLGA-BG composite scaffolds, we tested whether solution-mediated factors derived from composite scaffolds/hybrids can promote osteogenesis of marrow stromal cells. The dissolution product from PLGA-30%BG scaffold stimulated osteogenesis of MSC, as was confirmed by increased mRNA expression of osteoblastic markers such as osteocalcin (OCN), alkaline phosphatase (ALP), and bone sialoprotein (BSP). The three-dimensional structure of the scaffolds may contribute to the production of cell derived factors which promoted distant MSC differentiation. Thus PLGA-BG composites demonstrates significant potential as a bone replacement material.