Papers by Keyword: BCP

Abstract: The present report aims to fabricate biphasic calcium phosphate (BCP) biocomposite in order to study the effects of sintering temperature on the sintered BCP biocomposite characteristics (phase’s formation, porosity and hardness properties). These effects were quantified using design of experiment (DOE) to develop mathematical models. BCP biocomposite pellets (60 wt% HA) were fabricated using mixing, pressing and sintered at two different temperatures (1100°C and 1250°C). The experiment was run by following the run order suggested by DOE software (Minitab 16) through randomization stage. Results show that sintering temperature will affect the formation of α-tricalcium phosphate (α-TCP) and the porosity of the samples. The formation of α-TCP phases will reduce the hardness value of BCP biocomposite.

Abstract: The processing of porous ceramics spheres (PCS) has been developed for biphasic calcium phosphates (BCP), hydroxyapatite (HAp) and beta tricalcium phosphate (β-TCP) in order to be used mostly as bone fillers and drug delivery systems. The importance of the PCS is due to better accommodation of them in order to fill empty spaces and also because is more friendly to cells and bone tissue growth. Also is important to obtain a surface roughness to increase the surface area in contact with the living tissue and their fluids. There are several methods used to achieve the PCS form and most of them use suspensions based on liquids immiscibility effect or additives. The aim of this work was to achieve PCS of BCP, HAp and β-TCP with rough surface and varying size without using solutions or additives. The method developed is based on a mechanical continuous movement of the particles, relying on the normal ability of the ceramic powders to aggregate themselves while rolling in a cylindrical container for long periods. The physical forces involved in the process, gravity, particle attraction, centripetal force and shocking make the ceramic rounds with golf ball appearance on its surface. With this method it was possible obtain PCS with 30% of porosity with rough surface and size between 1 to 4 mm in diameter.

Abstract: The biphasic calcium phosphate (BCP) concept was introduced to overcome disadvantages of single phase biomaterials. In this study, we prepared BCP from nanoHA and β-TCP that were synthesized via a solid state reaction. Three different ratios of pure BCP and collagen-based BCP scaffolds (%HA/%β-TCP; 30/70, 40/60 and 50/50) were produced using a polymeric sponge method. Physical and mechanical properties of all materials and scaffolds were investigated. XRD pattern proved the purity of each HA, β-TCP and BCP. SEM showed overall distribution of macropores (80-200 µm) with appropriate interconnected porosities. Total porosity of pure BCP (93% ± 2) was found to be higher than collagen-based BCP (85%± 3). It was observed that dimensional shrinkage of larger scaffold (39% ± 4) is lower than smaller one (42% ± 5) and scaffolds with higher HA (50%) ratio experienced greater shrinkage than those with higher β-TCP (70%) ratio (45% ±3 and 36% ±1 respectively). Mechanical properties of both groups tend to be very low and collagen coating had no influence on mechanical behavior. Further studies may improve the physical properties of these composite BCP.

Abstract: Orthopedics surgeries frequently are open surgeries, but the improvement of the specific instrumentation and the use of bioresorbable polymerics implants for regeneration of bone fractures are contributing to the development of noninvasive techniques such as an injectable bone substitute. These injectable materials are composites, formed by a particulate ceramic phase and a polymeric phase, and have the advantages of combining bioactivity and the ability to control degradation and some mechanical properties. In addition, microparticles present flexibility to fill several types of defects with closer packing and allow new bone growth and vascularization through the interconnected pores formed by the spaces between them. Another advantage of the particulate materials is that they have the potential to incorporate drugs such as antibiotics that can be applied in situ for treatment or prevention of bone infection, which is important because the poor circulation of blood in the osseous tissues makes necessary large amounts of these drugs to guarantee that an adequate dose reaches the affected site. This work evaluates the release potential of gentamicin from BCP spherical microparticles to be used in osseous injectable implants. The particles present a smooth geometry to prevent inflammatory reactions frequently caused by an irregular morphology, and their compositions offer a combination of biodegradability and stability. Microparticles with diameters between 150-425µm, were obtained by a method based on the immiscibility of liquids. To encapsulate the antibiotic, the spheres were immersed in a gentamicin solution, and after 24h they were separated and dried. The evaluation of the gentamicin release from the microspheres was carried out at 37°C in PBS, and the release medium was collected at predetermined time intervals for measurement of the amount released. This work demonstrates that these microspheres can find potential application in bone repair and regeneration.

Abstract: In the present study, an Intelligent Multi-parameter Simulated Evaluation in vitro （IMSE system） was used to study the deposition properties of apatite formation on the surface of biphasic calcium phosphate porous ceramic (BCP) from static and dynamic r-SBF. Results showed that apatite formed on the surface of BCP from static and dynamic r-SBF differed between each other. In static r-SBF, ions were transferred by diffusion, which could not compensate the consuming of calcium ions, and mist apatite layer was formed on the surface of samples. But in the dynamic r-SBF, simulated fluid was adjusted precisely and flowed forcedly, the concentrations of ions were homogeneous; with the compensation of ions, calcium and phosphate were supersaturated, and the free energy of apatite formation was negative, bone-like apatite sheets were formed on the surface of samples.

Abstract: Biphasic calcium phosphate powders (BCP) of hydroxyapatite (HA) and tricalcium phosphate (β-TCP) with the various ratio of HA to β-TCP were prepared by utilizing mechanochemical synthesis. Calcium hydrogen-phosphate dihydrate (brushite, CaHPO4⋅2H2O) and calcium carbonate (calcite, CaCO3) powders have been chosen as the starting materials. The original Ca/P ratio of CaHPO4⋅2H2O - CaCO3 batch was set to be 1.67. A mixture of starting materials was milled using a planetary mill (ZrO2 jar and balls) with water for 3, 4, 5, 6 and 7 hrs. The XRD study of calcined powders was conducted for phase identification and for HA/β-TCP ratio as well. The phases of the calcined powders were HA and β-TCP, and the HA/β-TCP ratio varied with the milling time. The mass fraction of HA and β-TCP phases was calculated from the XRD intensities of HA and β-TCP. The ratio of the mixture milled for 4 hrs and calcined at 900°C was 85(HA):15(β-TCP) (BCP 85/15) and the content of β-TCP increased with the milling time. It is believed defective HA powder formed at relatively short period of milling time (less than 3 hrs The research revealed that nanocrystalline BCP powders could be synthesized by an employment of a medium-high energy mechanical activation at room temperatures (~25°C) without any preliminary chemical processing.

Abstract: Studying on the interaction between proteins and calcium phosphate implants is one of the basic subjects in biomaterials science and engineering. In this work, zeta potentials and contact angles of hydroxyapatite (HA) and biphasic calcium phosphate (BCP) ceramics were measured, and the adsorption behaviors of bovine serum albumin (BSA) on the surfaces were investigated. The adsorption isotherms of BSA on both ceramics follow the Langmuir type, however, BCP shows higher BSA adsorption ability. The differences of contact angles and zeta potentials in HA and BCP are the key factors to determine their ability to bind BSA molecules.