Bioceramics Development and Applications

Amorphous calcium polyphosphate (CPP) has potential as an implantable drug delivery matrix by virtue of a low temperature gelling protocol that has been shown to eliminate burst release and extend drug release time from the matrix. However, a greater understanding of this material’s interaction with aqueous environments is needed to more fully exploit this application. Variations in aqueous exposure were assessed using as-made amorphous CPP as well as CPP processed using established low temperature protocols. Solid-state 31P-NMR along with thermal and X-ray diffraction analyses were used to track resulting structural changes. Exposure to aqueous environments caused a reduction in CPP chain length that was dependant on gel time and mode of exposure. Significantly, increased gel times or water availability further resulted in crystallization events upon drying, except in the presence of a buffered solution. In general, drug elution studies showed an increase in the burst release of vancomycin from CPP disks gelled for extended periods, with matrix-water interactions appearing to be most influential during the drug loading stage. Overall, this study shows that CPP drug delivery matrices can be produced with tailored properties by closely controlling CPP-water interactions during processing.

We developed a novel thermal spraying technology for a silver-containing hydroxyapatite (Ag-HA) coating with antibacterial activity to reduce the incidence of implant-associated infections. In this study, we determined the concentration of Ag ions that show antibacterial activity in fetal bovine serum (FBS) and antibacterial activity of the Ag-HA coating in FBS. The minimum inhibitory concentration (MIC) of Ag ions for several bacteria in FBS was in the range of 4.0–7.9 ppm. When 10 ppm Ag were added (as AgNO3 solution), 0.01 ppm of free Ag ions was detected. As the MIC of Ag ions approached the concentration that enabled formation of free Ag ions in FBS, the antibacterial activity of added Ag can be attributed to the free Ag ions. The Ag-HA coating showed strong antibacterial activity in FBS as well; the Ag concentration in FBS was 26 ppm for the antibacterial test of the Ag-HA coating. Because the Ag-HA coating can release sufficient free Ag ions in FBS, we observed that the Ag-HA coating shows a strong antibacterial effect in the biological medium studied.

Objective. The aim of the present study is to prepare a 3D porous silk fibroin scaffold with a hierachical structure that can meet the demands for bone tissue engineering. Materials and Methods. 3D fibroin scaffold was prepared by the methods of partial dissolution in acid solution and freeze drying fibroin solution. Results. The nets were composed of a mesh of randomly oriented fibers that ranged between 10 ?m and 30 ?m in diameter. Branchpoints and three dimensional open spaces were distributed throughout the structure with an average pore size of about 177.9 ± 40.0 ?m. Conclusion. With the methods of non-woven silk fibroin net preparation and frozen-dried technics, it is possible to prepare a 3D porous silk fibroin scaffold with hierachical fine structure.

Difference in osteoclast responses (i.e., apoptosis, actin ring formation) to tricalcium phosphate (TCP) in culture medium supplemented with zinc and to zinc-containing tricalcium phosphate (ZnTCP) was investigated in this study. On the TCP ceramic, an increase in zinc ion in the culture medium within the range between 0.3 and 6.8 ppm significantly induced an increase in osteoclast apoptosis and a decrease in actin ring formation. However, even a high level of magnesium ion up to 100 ppm in the culture medium or up to 6.8mol% in the ceramic was unlikely to influence osteoclast activity. There was almost no significant difference in osteoclast apoptosis and actin ring formation between ZnTCP with 1mol% zinc and magnesiumcontaining tricalcium phosphate with 1.5mol% magnesium ceramic which have the same solubility and the same dissolution rate. It is suggested that only an increase in zinc level outside resorption lacuna has an inhibitory effect on osteoclast resorption and that an increase in zinc level inside resorption lacuna could not influence osteoclast activity.

Template-assisted electrohydrodynamic atomisation (TAEA) spraying of nanometer-sized siliconsubstituted hydroxyapatite (nanoSiHA) was used to pattern implant surfaces for guided cell growth to improve the repair and regeneration of medical implants. A suspension of nanoSiHA was prepared and characterized. Patterns of pillars and tracks of various dimensions were prepared using the suspension. It was found that the resolution of the pattern was affected by TAEA processing parameters, such as applied voltage, flow rate, distance between needle and substrate, and spray time. Fifteen minutes spraying time provided the most clear and uniform patterned topography with a distance between nozzle and substrate of 50mm and a flow rate of 4?l/min. Therefore, well-defined nanoSiHA patterns can be achieved by TAEA deposition, it thus offers great potential for patterning the surface of medical implants.

Discs of poly carbonate urethane (PCU) were coated with a thin layer of calcium phosphate (CaP) by a biomimetic process at temperatures of 28?C and 37?C. The coating morphology was analyzed by SEM. Contact angle analysis was used to assess surface wettability. Human osteoblasts (HOBs) were cultured on uncoated and CaP-coated PCU discs for up to 14 days. Cell metabolism, structure, and morphology were analyzed and compared with the wettability of each sample group. HOBs proliferated and grew on uncoated and CaP-coated samples, but a greater cell metabolism was observed for uncoated samples at early time points in cell culture. A more even dispersion of HOBs across the disc surface, attributable to the increased surface wettability, was seen for CaP-coated samples.

Understanding of interactions between cells and biomaterials is a huge parameter for improving tissue engineering and regenerative medical fields. Many different materials have already been tested (including calcium phosphate ceramics) and it has been established that surface characteristic is a parameter that influences cell responses. The aim of this work was to characterize calcium phosphate discs containing various ratios of HA/?-TCP and specific microstructure. First results show that chemical composition and compression parameters modify surface materials. Secondly, cells were cultured (osteoblast-like cells MC3T3- E1) and morphology, viability, and differentiation were studied. SEM observations, mitochondrial (MTS assay), and alkaline phosphatase activity (ALP) measurements showed that osteoblasts have better viability and a higher rate of differentiation when cultured on dense surface compared to porous surface. The aim of this experiment was to contribute to the knowledge of interactions between osteoblast-like cells and microstructured calcium phosphate bioceramics pellets.

Synthetic hydroxyapatite was modified with zinc and strontium by two methods: ion exchange and coprecipitation synthesis. Hydroxyapatite and metal modified hydroxyapatite samples were characterized by XRD, ICP-OES, and FTIR-DRS. BSA adsorption experiments were accomplished during 24 hours using 1.0mg/mL of protein. UV spectrometry was used to quantify the protein at 278 nm. The results suggest that metal presence on the surface or in the bulk of hydroxyapatite improves the protein adsorption efficiency. FTIR-DRS showed that the protein main secondary structure ?-Helix is involved in the adsorption process.

This study proposed a new strategy for preparing self-assembling one-dimensional HAp nanorods into organized superstructures. We employed glass of a few specific compositions in the system Na2O-CaO-SiO2 because it may yield Si-OH groups on the surface when soaked in an aqueous system, and their formation is one of the key factors to induce apatite nucleation. A nanometerscale rod array of HAp having preferred orientation to the c-axis was successfully prepared simply by soaking the soda-lime silica glass substrates in Na2HPO4 aqueous solution at 80 °C. Those HAp rods grew up perpendicularly to the glass surface, and the crystallites covered glass surface uniformly, resulting in “dental enamel-like� rod array structure. The present procedure is significant as it allows to design biomimetic materials and therapeutic agents with applicable both the biomedical and material science fields because the nano-textured HAp crystals exhibit a hierarchical architecture and may provide specific cell attachment and proliferation with controlled planes of growth and nano- and micrometer-scale topography.

Profile accuracy of spherical ?-TCP ceramics (artificial bone units) was improved by a precision fabrication method named “hydro-casting.� Hydro-casting shapes ?-TCP slurry into spherical shape by dispensing definite quantity of ?-TCP slurry in an oil and fixing the slurry’s shape by two-stage gellation. Resulting ?-TCP spheres exhibit almost uniform shape and interunit gaps that would establish schematic features of porous body fabricated by “Mosaic-like ceramics fabrication (MLCF).�

The response of human bone marrow cell to bone ash-derived hydroxyapatite (HA) and tuna bonederived HA powders was compared. HA ceramics were prepared from the commercial bone ash and waste of tuna bone. HA powders were prepared by soaking the bone ash and tuna bone in 0.1M of NaOH solution at 80 °C for 4 hours. Both powders were calcined at 800 °C for 1 hour to completely remove organic and were attritor-milled for 24 hours. The bone ash-derived HA (AHA) and tuna bone-derived HA (THA) ceramics were prepared by cold isostatically pressed and sintered 1200 °C with a dwell time of 1 hour. A human bone cell line MG-63 cells were used to test biocompatibility of AHA and THA ceramics. Cell suspensions in DMEM containing 10% FBS and 1% penicillin-streptomycin were seeded onto 24-well plate containing THA and AHA ceramics. Cell proliferation was evaluated by MTS assay, and cell morphology was observed by SEM.

Metal nanoparticles play an important role in many different areas such as catalysis, electronics, sensors, and cancer therapy. Silver, in its many oxidation states (Ag0, Ag+, Ag2+, and Ag3+), has long been recognized as having an inhibitory effect towards many bacterial strains and microorganisms commonly present in medical and industrial processes. Silver was introduced in various materials including hydroxyapatite due to its biocompatibility. The unique size-dependent properties of nanomaterials make them superior and indispensable. In this work, nanohydroxyapatite/polyvinylpyrrolidone composite was doped with 2 different concentrations of silver nanoparticles prepared by reduction method. Several techniques like TEM, XRD, FT-IR, and SEM with EDS were used to characterize the prepared samples. The bioactivity test (soaking in SBF) at different short time intervals was characterized by using inductively coupled plasma-optical emission spectroscopy (ICP-OES) method. It is demonstrated that silver-doped nanohydroxyapatite obviously improves the bioactivity of the apatite at the early stages of immersion. The antibacterial inhibition over 3 types of bacteria (Staphylococcus aureus, Streptococcus mutans, and Pseudomonas) is under investigation.

Bioactivity and osteoconductivity of calcium phosphates as a function of ?-tricalcium phosphate contents, that is, biodegradability, were investigated. Three calcium phosphates, pure hydroxyapatite, biphasic calcium phosphates with different mixing ratios between hydroxyapatite, and ?-tricalcium phosphate (60HAp:40?- TCP and 40HAp:60?-TCP in wt.%), were synthesized through the precipitation method using calcium hydroxide and phosphoric acid as starting reactants. After drying, they were sintered at 1100 °C for 3 hours, and then bioactivity and osteoconductivity tests were carried out in simulated body fluid (SBF) and calvarial defect of New Zealand white rabbits, respectively. SBF exposure resulted in the deposition of a layer of carbonate apatite crystals on the surfaces of bicalcium phosphates but not on the hydroxyapatite. New bone forming capacity of the biphasic calcium phosphate with 60HAp:40?-TCP granules was the best, whereas that of the pure HAp was the worst. To this end, it can be concluded that the calcium phosphate with moderate biodegradability is good for producing good osteoconductivity.

In order to establish a reasonable biomimetic condition for compressive strength of bioactive ceramics, the compressive strengths of several commercial bioactive ceramics were measured under various conditions. All specimens except for one of Japanese ceramics, specimen A, showed no significant differences among the conditions, but showed a tendency of decreasing the compressive strength more than 10% in comparison to the dry condition that was conventionally described in product brochures. Further, the specimen A indicated a significant decrease of the compressive strength in 24 h soaking conditions. Accordingly, a recommended biomimetic condition would be that specimen would be soaked in PBS after deaeration at 25 °C for 24 h and measured in air after brief wiping surface liquid.

In this article, the mechanical characterization of a monolithic cup made of BIOLOXdelta with a porous ceramic coating for osseointegration is presented. During the coating process, a ceramic slurry is deposited on a green substrate, both slurry and substrate are based on BIOLOXdelta. To achieve a porous coating, organic pore-forming agents were used which are pyrolized in the following sintering process. Porosities of 18 to 47% could be reached depending on the layer thickness. Extensive mechanical investigations were applied on the fabricated cups to verify the suitability of the produced porous layers for biomechanical demands of the interface between bone and dense substrate. The test results showed that coated ceramic cups require comparable push out forces for the disconnection from artificial bone to established metal shells with plasma sprayed titanium coatings.

Porous titanium (Ti) metal with a structure similar to that of human cancellous bone was fabricated by selective laser melting (SLM) process. SEM observation showed that the core part of the walls of the porous body was completely melted by the laser beam and weakly bonded with small Ti particles on its surface. These Ti particles were joined with the core part by heating above 1000 °C, with remaining micro cavities on their surfaces. Tensile strength of the as-prepared solid rod was 530MPa and gradually decreased with increasing temperatures to 400MPa at 1300 °C, whereas its ductility increased with increasing temperatures. NaOH treatment formed fine network structure of sodium hydrogen titanate (SHT) on the walls of the porous Ti metal. The SHT was transformed into hydrogen titanates by HCl treatment and finally anatase and rutile by the heat treatment. Thus treated porous Ti metal formed apatite on its surface in simulated body fluid (SBF) within 3 days.

A biphasic calcium phosphate (BCP) powder is synthesized, mixed with various amounts of naphthalene particles, pressed and sintered at different temperatures to obtain ceramics with isolated macropores (from 3% to 52% of the specimen volume) and residual microporosity resulting from an incomplete sintering (from 2% to 45% of the ceramic matrix volume). Young’s modulus is measured on a classical three-point bending setup. A good agreement is found between an existing analytical model and the experimental Young’s modulus measurements, on the overall ranges of macro- and microporosity. The Young’s modulus variation as a function of macroporosity is also calculated by a finite element method, by simulating the mechanical response of a periodic tri-dimensional repetition of elemental cubes containing various dispersions of macropores. The contribution of the shape and dispersion (in size and location) of the macropores on the decrease of Young’s modulus as a function of porosity is simulated. Calculated trends are confirmed by experimental results.

Objective. The aim of the present study is to prepare a 3D porous silk fibroin scaffold with a hierachical structure that can meet the demands for bone tissue engineering. Materials and Methods. 3D fibroin scaffold was prepared by the methods of partial dissolution in acid solution and freeze drying fibroin solution. Results. The nets were composed of a mesh of randomly oriented fibers that ranged between 10 ?m and 30 ?m in diameter. Branchpoints and three dimensional open spaces were distributed throughout the structure with an average pore size of about 177.9 ± 40.0 ?m. Conclusion. With the methods of non-woven silk fibroin net preparation and frozen-dried technics, it is possible to prepare a 3D porous silk fibroin scaffold with hierachical fine structure.

Due to osteoconductivity of hydroxyapatite (HA), HA/polymer composite scaffolds have been investigated for bone tissue engineering by various groups. In scaffold fabrication, electrospinning of ultrafine fibrous scaffolds incorporated with substantial amounts of evenly distributed HA nanoparticles is still a challenge. The problem of nanoparticle agglomeration not only reduces the electrospinning efficiency but also undermines the homogeneity of the distribution of the HA nanoparticles along the fibers. In this study, an approach using ultrasonification was developed so as to electrospin fibrous nanocomposite scaffolds having the carbonated HA (CHA) nanosphere content up to about 15 wt% with minimal agglomeration of CHA nanospheres. SEM and EDX results showed an even distribution of CHA nanospheres while FTIR results further confirmed the presence of CHA within the electrospun fibers. The nanocomposite fibrous scaffolds fabricated through this route could be used in further investigations for bone tissue engineering applications.

Chitosan-?-glycidoxypropyltrimethoxysilane (GPTMS)-tetraethoxysilane (TEOS) hybrid membranes were prepared by a sol-gel method. Effects of Si(IV) released from them on proliferation and differentiation were examined in terms of cell metabolic activity and alkaline phosphatase (ALP) activity of MG63 osteoblastic cells. The amount of Si(IV) released from the hybrid membranes increased with the TEOS content. Released Si(IV) inhibited cell proliferation, while it promoted cell differentiation. Thus, osteocompatibility of the chitosan hybrid membranes can be controlled due to the amount of Si(IV) released from them as the hybrids in the system chitosan-GPTMS-TEOS are applied for cell culture.

The purpose of this study was to obtain an appropriate geometry of porous hydroxyapatite scaffold for hard tissue formation in most of the pores. Porous cylindrical hydroxyapatite structures with a hollow center as a scaffold were manufactured. The diameter of a hollow center was 2 or 3 mm. Bone marrow cells were obtained from bone shafts of femora of 6-week-old male Fischer 344 rats. The cell/hydroxyapatite composite scaffolds were implanted in dorsal subcutis of 7-week-old male Fischer 344 rats. They were removed 8 weeks postoperatively. Serially sectioned paraffin specimens were made and observed histologically. The ratio of pores including hard tissue to the number of total pores per a square centimeter of the cross-sectional area in the scaffolds was calculated. In the scaffold with a hollow center measuring 2mm in diameter, a new hard tissue formation was observed near the superficies and the number of pores including hard tissue was 260.6 ± 60.8/cm2. In the scaffold with a hollow center measuring 3mm in diameter, new hard tissue was observed between superficies and the wall of the hollow center. The number of pores including hard tissue was 589.6 ± 73.3/cm2.

Scaffolds are commonly used as cell’s vehicles in order to promote cell development. The aim of this study was to investigate the proliferation of human periodontal ligament fibroblasts (PDLF) in composite ceramic scaffolds. Chitin (CHN), chitosan (CHS) and chitosangelatin (CH-G) scaffolds were fabricated on the surface of ceramic disks, coated with a mixture of a bioactive glass modified ceramic. Cell proliferation was evaluated with the MTS method. All composite ceramic scaffolds were successfully loaded with PDLF cells. However, only in CH-G composite ceramicscaffolds cell population progressively increased until day 7 and presented a sudden drop at day 10 before being stabilized for the rest of the testing period. In the case of CHN and CHS the cell number was progressively decreasing. The successful observed cellular response in CH-G composite ceramic scaffolds could support the development of a protocol for tissue engineering on the materials used.