Abstract: Fibronectin (FN)-apatite composite layers were formed on a hydroxyapatite (HAP) ceramic using supersaturated calcium phosphate (CP) solutions. The surface roughness of the composite layer could be controllable by changing the magnesium (Mg) concentration in the CP solution. The higher the Mg concentration, the smaller the apatite crystals in the layer were. The
thickness of the layer formed in the CP solution containing 1.5 mM Mg decreased to 68% that formed in the Mg-free CP solution. The amount of FN immobilized in the layer was almost constant regardless of Mg concentration in the CP solution in the range from 0 to 1.5 mM. The results of the present study revealed that a thin FN-apatite composite layer with a smooth surface and a high protein content is formed in a CP solution at a Mg concentration of 1.5 mM.
Abstract: Cultured osteoblasts with mineralized matrix (regenerative cultured bone; RCB) have been used for patients having osseous defects. The RCB can be fabricated on various ceramic substrata using patient’s mesenchymal stem cells (MSCs) at our cell processing center (CPC). Since we have to transport the RCB for hospitals outside of our town, the RCB should maintain the cell viability for a
long time. To determine a suitable condition for transportation of the RCB, stability of the RCB was analyzed by biochemical assays. Even outside CO2 incubator, the RCB kept high level of viability until 24 hours at 25°C and also showed low level of cytotoxicity for 24 hours at 37°C and 25°C. On the other hand, the RCB incubated for 24 hours at 4°C outside CO2 incubator resulted in extremely
low level of viability with obvious cytotoxicity. These data indicated that stability of the RCB can be maintained for 24 hours at 37°C and 25°C, but not at 4°C. Therefore, the RCB derived from patient’s MSCs can be transported and utilized for the patients at hospitals far away from the CPC.
Abstract: To promote the activity of normal human osteoblasts (NHOst), the novel HAp ceramics containing Nb ions (NbHAp) were synthesized by wet chemical process, which reacting aqueous solution containing a mixture of Ca(NO3)2, (NH4)2HPO4, and the Nb aqueous solution. X-ray diffraction
patterns indicated that NbHAp had a monolithic apatitic structure, although crystallite decreased as Nb content increased. From inductively coupled plasma analysis, maximum amount of Nb ions in the sample was almost 8.2atom% of P ions. The NbHAps were presented as aggregates and composed of fine crystal of <1µm in diameter. Nb ions in NbHAp were uniformly distributed in the aggregates. Furthermore, high-resolution XPS spectra of Nb 3d5/2 indicated that Nb ions in the
HAp were presented as Nb5+. These results suggested that Nb ions were at PO4 site in crystal structure of HAp. When NHOst were cultured with the NbHAp, their ALP activity were twice as much as that of NHOst cultured with HAp without Nb ions.
Abstract: Composites of calcinated bovine bone derived hydroxyapatite (HA) with 0.25, 0.5, 1, and 2 wt % La2O3 were prepared by sintering. The experimental results indicated that compression strength and microhardness of HA-La2O3 composites increase when the content of La2O3 and sintering temperature increase. The best mechanical properties were achieved after sintering at 1300°C. The results are in agreement with densification measurements and microstructure analysis.
Abstract: Biocompatibility has long been associated with surface microtopography, microtexture and microchemistry. The surface topography ultimately affects the nature and the strength of the interactions that occur at biomaterial-biological environment (cell adhesion, mobility, spreading and proliferation). Thus, it is necessary to produce and work with controlled microtopographical surfaces that present reproducible microdomains of a dimension similar to that of the biological elements of interest (for instance, cells).  There are a number of substrates that already have been studied (such as silicone, polystyrene, poly-L-lactic acid and titanium coated polystyrene) in terms of surface topography.  However, few studies are related to hydroxyapatite substrates. As it is well established, hydroxyapatite is a well known ceramic that is extremely used in medical applications, namely implants and coatings. In this work, the surface topography of dense hydroxyapatite substrates was altered by using KFr excimer laser. Excimer lasers produce high-intensity, pulsed ultraviolet radiation and are especially well suited for materials processing due to their large beam cross-section area, which permits using mask projection technologies to process relatively large areas in a single step.
Abstract: There are two crystal planes in hydroxyapatite (Ca10(PO4)6(OH)2; HAp) that is clinically applied to artificial bone or dental root. The two crystal planes, a- and c-planes, are anisotropy. We have successfully fabricated dense HAp ceramics with preferred orientation to a-plane from single-crystal apatite fibers (AF) and apatite gels (AG). We examined the cellular response, such as adhesion, proliferation and morphology, of orthoclastic MC3T3-E1 cells, to the surface of the HAp ceramics with preferred orientation to a-plane. The initial cell attachment efficiency of the HAp ceramics with a-plane was lower than that
of isotropic HAp ceramics as a control. This may be due to the difference of surface potential of the examined HAp ceramics. The proliferation of cells cultured on the HAp ceramics with a-plane was almost the same as that of isotropic HAp one.
Abstract: Silicon-substituted hydroxyapatite (SiHA) attracts particular interest due its enhanced bioactivity compared with pure hydroxyapatite. In this study we seek to clarify the effects on the lattice parameters of both composition and sintering temperature in experimentally-produced HA and 0.8wt% SiHA, 1.5wt% SiHA and 2.0wt% SiHA sintered at 800oC and 1200oC. X ray diffraction was
used to determine the phase purity and crystallographic structure. We found that while the c parameter increased with increasing silicon concentration, the a parameter decreased with initial silicon incorporation then recovered with further increases in silicon incorporation. The calcium (2)
channel expanded with silicon incorporation while tetrahedron distortion index (TDI) and the radius of the P channel showed a similar dependence on silicon content as the a parameter.
Abstract: In this study silicon release from SiHA into tissue culture medium was investigated under static and semi-dynamic conditions. The effect of silicon release under semi-dynamic conditions on alkaline phosphatase activity (ALP) and collagen I (CICP) expression by osteoblast like cells (HOS TE85)
was also examined. Under static conditions a low level of silicon was released within 24 hours, this initial level dropped over 3-7 days but subsequently increased again by 10-14 days. Under semi-dynamic conditions silicon was released within 24 hours and was subsequently reduced with each medium change until
equilibrating at close to 0 after 10 days. ALP and CICP showed significant variation in expression between culture conditions. In direct contact with SiHA ALP peaked at day 10 and CICP was constantly elevated. Cells grown in the presence of but not on SiHA expressed progressively decreasing levels of ALP from 7-14 days, with CICP peaking at day 10. On thermanox (TMX) ALP constantly increased and CICP peaked at day 10. The results indicate that silicon leaches out of the
lattice of the SiHA crystal structure but may also be reprecipitated onto the substrate. We have also demonstrated that Si influences osteoblast metabolism and differentiation whether it is available as free silicon or 'bound' in the apatite lattice.
Abstract: The object of this study was to investigate the effect of the concentration of orthosilicic acid (0, 0.5, 1, 5 and 10µM) on gene expression in human osteoblast cells isolated from trabecular bone. This was measured using reverse transcriptase-polymerase chain reaction (RT-PCR) to quantify messenger RNA (mRNA) levels for collagen type I, alkaline phosphatase and osteocalcin.
Results showed that while collagen type I mRNA expression was increased by the addition of up to 10µM orthosilicic acid, ALP message was suppressed over time and osteocalcin levels were decreased.