Masataka Ohgaki

Manipulation of selective cell adhesion and growth by surface charges of electrically polarized hydroxyapatite.

Adherence of cells to a surface, such as a biomaterial surface, can be significantly influenced by the surface charge on that material. The applicability of electrically charged hydroxyapatite ceramics to selective cell adhesion was examined, and we show that polarized hydroxyapatite has significant effects on cell growth and adhesion. The surface charge applied to polarized hydroxyapatite promotes (i) enhanced colony formation of osteoblast-like cells, (ii) activation of gap junctions, and (iii) specific orienting of neuroblastoma cells. These findings will be of great utility and have significance in applications of tissue engineering, for example, in potential treatments for osteoporosis.

A New Approach to Enhancement of Bone Formation by Electrically Polarized Hydroxyapatite

An electrical field may affect osteogenesis. Since we found that hydroxyapatite (HA) ceramics may be polarizable, we hypothesized that electrically polarized HA may foster production of new bone in vivo. Both polarized and non-polarized HA ceramics were inserted into the subperiosteum spaces at the parietal bone area of rats. After 2, 4, and 8 weeks, the implant sites were examined histologically. Morphometric analysis revealed that new bone formation was accelerated on the negatively charged surface of the polarized HA (N-surface) at 2 weeks. The newly formed bone approached maturation at 4 weeks and was thicker on the N-surface than in the controls. By 8 weeks, newly formed bone in the controls was almost the same as that on the N-surface. These findings suggest that polarized HA is biocompatible and that bone formation on the N-surface is enhanced in the early stage of bone healing.

Effect of bone-like layer growth from culture medium on adherence of osteoblast-like cells

The electrical polarization of ceramic HAp had an effect on the acceleration of bone restoration. Cell behavior in the bone-like growth layer was investigated. The deposits on the ceramic HAp was grown and formed layers by soaking in alpha-minimum essential medium supplemented with 10% fetal bovine serum (alpha-MEM supplemented with 10% FBS). The shapes of the adhering cells on the grown layer gradually changed from spindle to flat with growth of the layer. On the totally grown layer that was grown on the ceramic HAp by soaking in alpha-MEM supplemented with 10% FBS for 7 days, all the adhering cells were flat and the surface was filled with the grown cells. From these results, it was revealed that the grown layer on the ceramic HAp is one of the activation factors of cell growth. Consequently, cell growth was reinforced by acceleration of the layer growth on the negatively charged surface of the polarized ceramic HAp.

Application of hydroxyapatite-sol as drug carrier

The application of hydroxyapatite-sol as a drug carrier is being developed. Hydroxyapatite-sol which is a suspension consisting of hydroxyapatite nano-crystals, was synthesized using an ultrasonic homogenizer. The size of the crystals was 40 x 15 x 10 mm3 on average and their specific surface area was 100 m2/g. An amount of a glycoside antibiotics adsorbed onto hydroxyapatite nano-crystals was measured. The drug adsorbed 0.2 mg per 1 mg of hydroxyapatite. The affect of the drug adsorbed onto the hydroxyapatite was investigated using cancer cells. The drug, adsorbed onto the hydroxyapatite nano-crystals, inhibited cancer cell growth.

Electrovectorial effect of polarized hydroxyapatite on quasi-epitaxial growth at nano-interfaces

Abstract Controllability of crystal growth on polarized hydroxyapatite (HAp) associated with simulated body fluid (SBF) was studied. Polarizing microscopic observation showed the crystal layer with c-axis vertically oriented to the polarized HAp surface. Scanning electron microscopic observation (SEM) showed an initial growth of the crystal. Structurally and micromorphologically oriented particles were precipitated on the surfaces of polarized HAp ceramics. Confocal laser scanning microscopic observation (CLSM) revealed higher Ca2+ concentration near negatively polarized surfaces. The polarization on HAp may make the crystal deposition with an orientation, and an electrostatic field to the ambient ions.

Crystal growth and structure analysis of Sm 2− x Ce x CuO 4

The phase diagram of the Sm 2 O 3 –CuO system was investigated by the combination of the differential thermal analysis and the quench method. The results showed that Sm 2 CuO 4 incongruently melts at about 1220 °C, and that the solid Sm 2 CuO 4 exists in equilibrium with the liquid consisting of 81–95 mol% CuO in the range of 1060–1220 °C. On the basis of the phase diagram, Sm 2− x Ce x CuO 4 single crystals were grown by the traveling solvent floating zone method. The crystal structure [space group I 4/ mmm , a = 3.917(1), c 4 11.899(2) A] has been refined using single-crystal x-ray diffraction data with a precision corresponding to an R index of 0.02.

Conformation of self-assembled organic layer on the electrically polarized hydroxyapatite ceramics in nonaqueous solution

Abstract The conformation of organic compound deposited on hydroxyapatite (HAp) ceramics was manipulated by their surface charge induced by electrical polarization. The sintered HAp ceramics were electrically polarized in a d.c. field at 400 °C. The organic layers on the HAp ceramics were deposited from a toluene solution of phenyltrichlorosilane (PTCS). The results of contact angle measurements and IR spectroscopy clarified the organic layer containing the fragments of PTCS. The amount of the obtained layer on the positively charged surface was larger than those on the negatively charged and nonpolarized surfaces. The thickness of the layer on the nonpolarized surfaces was thinner than those on the polarized surfaces, based on the depth profiles of Ca2p and Si2p. Although the deposition prepared on the nonpolarized HAp surfaces from the PTCS solution was supposed to be a self-assembled layer including of phenyl–Si bond, the layers on the polarized HAp were aggregated irregularly. Consequently, the HAp ceramic surface charge induced by the polarization altered the electrostatic interaction to the organic compounds in nonaqueous system.

Synthesis of New Biocompatible Apatite-Type Rare-Earth Silicates

Series of apatite-type rare-earth silicates were synthesi zed by a solid state reaction at 1400 °C as a new biomaterial. The synthesized apatite-type rare-earth silicate s were analyzed by X-ray diffraction (XRD) and infrared spectroscopy (IR), and lattice parameters we e calculated. Single phase of the apatite-type rare-earth silicates was obtained, and the lattic e parameters became smaller with the increase of the rare-earth content or increasing of an atomic numbe r of the substituted ions. The ceramic apatite-type rare-earth silicates were obtained by a sintering at 1400 °C, and its biocompatibility was estimated by in vitro and in vivo tests. The ceramic apatite-type rare-earth silicates had a good cell proliferation, and no inflammation was obser ved in the vicinity of the implanted ceramic. It was suggested that the ceramic apatite -type rare-earth silicates could use as a biocompatible material.

In vitro interaction of carcinostatic substances adsorbed on hydroxyapatite microcrystals with cells derived from cancers

Hydroxyapatite microcrystals were synthesized by a neutral reaction of Ca(OH)2 suspension and H3PO4 aqueous solution using an ultrasonic homogenizer. The in vitro influence of hydroxyapatite microcrystals with the drug on cancer cell growth was investigated using Ca-9 and HSC-3 cells. The crystal shapes were plate-like, less than 0.1μm. The secondary particle sizes of the aggregated crystals dispersed into a physiological salt solution were determined as 1-10μm by a scattering laser diffraction method. The cell growth was drastically restricted by addition of hydroxyapatite microcrystals with doxorubicin hydrochloride compared to additions of doxorubicin hydrochloride alone and hydroxyapatite microcrystals alone. it was concluded that hydroxyapatite microcrystals are safe, absorbable, and very effective materials as new drug carriers for DDS.

Crystal Chemistry and Biocompatibility of α-TCP produced from β-TCP by a Plasma Spraying Technique

Abstract Titanium coated with α-TCP was prepared by plasma spraying β-TCP powders on titanium. The a-TCP coating was examined crystal chemically by the X-ray diffraction method. Moreover, the biocompatibility of a-TCP was examined by animal testing. The a-TCP coated on titanium was resorbable in bone tissue and had good compatibility, as did hydroxyapatite.