Papers by Keyword: Calcium Phosphate Ceramic

Abstract: Local drug delivery devices especially based on osteoconductive porous calcium phosphate ceramics are of clinical importance. However, the brittleness, pore structure, porosity and pore size should be controlled for their wider applications in hard tissue implants and load bearing compartments. An approach to the fabrication of the bone graft exhibiting bone regeneration function as well as the local drug delivery was made. Hydroxyapatite (HAp)/β-tricalcium phosphate (β-TCP) porous scaffolds were prepared and mechanical properties (compression strength 20MPa), porosity (>50%), pore size (60-350µm) and structure as well as interconnectivity of pores were investigated. Porous scaffolds were impregnated with 4-5 mg of lidocaine hydrochloride (LidHCl) and drug release rate was evaluated and compared for scaffolds with and without poly lactic acid (PLA), poly(-caprolactone) (PCL) and polyvinyl alcohol (PVA) coatings. From in vitro dissolution tests it was seen that biopolymer coatings sustained the drug release up to 12h.

Abstract: Calcium phosphate ceramics such as hydroxy apatite (HA), β-tricalcium phosphate (β-TCP) and bicalcium phosphate (BCP) have been used as a bone graft biomaterial because of their good biocompatibility and similarity of chemical composition to natural bones. To increase the mechanical and osteoconductive properties, the granules and spongy type porous bone graft substitutes were prepared by fibrous monolithic process and polyurethane foam replica methods, respectively. The pore sizes obtained using these approaches ranged between 100-600 µm. The cytotoxicity, cellular proliferation, differentiation and ECM deposition on the bone graft substitutes were observed by SEM and confocal microscopy. Moreover, the scaffolds were implanted in the rabbit femur. New bone formation and biodegradation of bone graft were observed through follow-up X-ray, micro-CT analysis and histological findings. After several months (2, 3, 6, 12 and 24 months) of implantation, new bone formation and ingrowths were observed in defect sites of the animal by CaP ceramics and 2 to 3 times higher bone ingrowths were confirmed than that of the normal trabecular bones in terms of total bone volume (BV).

Abstract: The use of bone grafts is constantly increasing, their employ is principally linked to bone trauma, prosthesis revision surgery, and arthrodesis applications. In the case of biological bone grafts and depending on the origin of the graft, these grafts are classified as autografts, allografts, or xenografts. The autograft is the most commonly used and corresponds to a fresh bone graft harvesting taken from a second operating site, i.e. iliac crest, parietal bone, tibial plateaux or the fibula. The autograft has many advantages in terms of biotolerance and osteogenic potential, which justify its widespread utilization in reconstructive surgery[1]. From a practical point of view, sampling and grafting take place during the same surgical session. However, the longer exposure to the anesthetic and the surgical operation per se increases the risk of complications. For example, this procedure results in sever post-operation pain, iliac hernias, or even haemorrhages[2]. Furthermore, the volume of the bone graft taken is generally limited to 20 cm3. In the case of allografts, it generally leads to an acute inflammatory reaction which participates to the resorption/substitution process. Xenografts are less used since it involves a donor and a recipient from different species.

Abstract: Micrometric sphere beads of HA-alginate composite were produced to remove Pb2+ and Cd2+ from contaminated gastric fluid. It was shown that the composite was effective in Pb2+ and Cd2+ immobilization from high-contaminated simulated gastric fluid. X-ray diffraction and scanning electron microscope analyses performed on HA-alginate beads after the Pb2+ uptake showed that lead phosphate, (Pb10-x Cax (PO4)6Cl2), was precipitated on beads surface. X-ray diffraction patterns of HA powder after Cd2+ sorption experiments showed no evidence of other phases, however, dispersive energy spectrometer analyses of the HA-alginate confirmed the presence of Cd2+ on the composite surface. Desorption experiments in simulated enteric fluid showed that composite beads containing Pb2+ and Cd2+ remained stables for one hour in simulated gastrointestinal fluid. The results reinforce the hypothesis that HA-alginate composite can be a very efficient system for Pb2+ and Cd2+ uptake from contaminated gastrointestinal fluid preventing systemic contamination by bloody stream uptake.

Abstract: This study aims at evaluating bone growth in critical-sized femoral defects of rats filled with macro micro porous biphasic calcium phosphate ceramic (MBCP) cylinders surrounded or not by a resorbable collagen membrane. Femoral defects left empty (control) exhibited partial bone ingrowths after 3 and 6 weeks and were completely healed at 12 weeks. The defects filled with the collagen membranes appeared partially healed suggesting that the membranes constraint bone ingrowth. Bone formation occurred around the collagen membrane which partially degraded over time. In the MBCP/membrane group, bone has grown inside the macro pores of the MBCP cylinders. Bone ingrowth was more rapid and abundant in the defects filled with MBCP alone. The combination MBCP/collagen membrane may be beneficial for the reconstruction of large bone defects without using repetitive surgeries and autologous bone grafting.

Abstract: In this study we show that mechanical properties of bioceramic scaffolds can be significantly improved by repeated infiltration with a low-viscosity polycaprolactone solution. Biphasic calcium phosphate (BCP: 70% hydroxyapatite, 30% β-tricalcium phosphate) scaffolds characterized by a bimodal pore size distribution and a global porosity of 70% have been chosen as starting materials. Polymer content in the ceramic scaffold was varied so that an inorganic/organic ratio close to that of bone may be achieved. Work of fracture at maximum stress was 36 J/m2 for the ceramic scaffold alone and reached 127 J/m2 for the 8-times infiltrated samples. These results are superior to the ones previously obtained with polycaprolactone infiltrated alumina due to higher micropore content. We show that during bending tests, polycaprolactone phase formed fibrils while the crack propagated. Crack bridging by polycaprolactone ensured the integrity of the composite once the ceramic scaffold was broken and directly involved in the composite toughening. Because of its composition, microstructure and mechanical behavior of this kind composite can be an interesting candidate for bone substitution.

Abstract: It is well known that calcium phosphate compounds are widely used as bone substitute due to their biocompatibility and bioactivity. Furthermore, recent studies have shown that slight changes in morphology or crystal structure can lead to several in vivo behaviours. Therefore, the purpose of this study was to investigate two different β-TCP synthesis routes (solid state reaction and aqueous solution precipitation) and their consequences on the final cement properties. It was found out that both routes are equivalent as there were no significant differences on their cement properties, except for mechanical resistance. The latter difference can also be attributed to the difference on the particle size distributions of the obtained β-TCP. These facts indicate that solid state reaction route is more interesting given its simplicity and yield.

Abstract: In the last few years new fabrication methods, called rapid prototyping (RP) techniques, have been developed for the fabrication of hydroxyapatite scaffolds for bone substitutes or tissue engineering applications. With this generative fabrication technology an individual tailoring of the scaffold characteristics can be realised. In this work two RP techniques, a direct (dispense-plotting) and an indirect one (negative mould technique), are described by means of fabricating hydroxyapatite (HA) scaffolds for bone substitutes or bone tissue engineering. The produced scaffolds were characterised, mainly regarding their pore and strut characteristics. By these data the performance of the two fabrication techniques was compared. Dispense-plotting turned out to be the faster technique while the negative mould method was better suited for the fabrication of exact pore and strut geometries.

Abstract: The aim of this study is to analyse the influence of differently fabricated HA-scaffolds on bone marrow stromal cells. Therefore, three methods were used (a polyurethane (PU)-replica technique, the dispense-plotting and a negative mould technique) to produce porous hydroxyapatite (HA) ceramics. The different HA-scaffolds were then cultivated with an osteoblastic precursor cell line. In our study, highest cell proliferation and differentiation was achieved by using (PU)-replica technique. However, this study shows also that all three types of scaffolds are suitable for tissue engineering applications and as bone substitute material. The knowledge about the influence of pore size and geometry on the cell behaviour will help to tailor scaffolds, by different 3D fabrication methods, for the needs of tissue engineering laboratories or patients.

Abstract: Recently, nanomaterials have received considerable attention because of their potential applications in the biomedical field. In the present study, we investigated the effects of nano-sized calcium metaphosphate (CMP) particles (50 nm) compared with micro-sized CMP particles (200-500 nm and 10 μm) on the proliferation and osteoblastic differentiation of human bone marrow stem cells (BMSCs). BMSCs were challenged with CMP particles with different sizes for 3, 5, and 7 days. An analysis of the proliferation revealed that the nano-sized CMP particles (50 nm) stimulated the proliferation of BMSCs up to 27.79% compared to the untreated control. This stimulatory effect of the nano-sized CMP particle was dose-dependent. CMP particles appeared to adhere on the surface of BMSCs but this did not cause distinguishable morphological changes. Moreover, all CMP particles (50 nm to 10 μm) were capable of stimulating an osteoblastic differentiation of BMSCs as accessed by alkaline phosphatase (ALP) and von Kossa stainings. Further molecular analysis revealed that all the CMP particles induced an expression of osteoblast-related genes such as osteocalcin (OC) and collagen I (Col I). Taken together, our data demonstrate that nano-sized CMP particles have the potential to stimulate the proliferation and osteoblastic differentiation of BMSCs.