EFFECT OF CROSSLINKING TO THE MECHANICAL PROPERTY OF APATITE GELATIN HYBRID FOR BONE SUBSTITUTION PURPOSES

The clinical success of current generation of synthetic bone substitute relies on bio-inspired design which has a performance level close to that of natural one. In this context, biomedical approaches are considered very important to result bio-functional hybrid for bone substitution purposes. In this study, effect of cross-linking to the mechanical properties of apatite gelatin hybrid has been investigated. Cross-linking was employed by 1-ethyl-3-3- dimethylaminopropyl carbodiimide (EDC) agent. The EDC agent creates a peptide bond between gelatin molecules inside the hybrid to the cross-linked structure. Cross-linked structure of gelatin increases physical property of the hybrid since it can hold the outer forces longer than that of without cross-linking

Effect of ice algal community on the increase of chlorophyll a concentration during spring in coastal water of the Sea of Okhotsk

A seasonal study of size fractionated chlorophyll α concentration was conducted weekly in Monbetsu Harbor from October 1996 to November 1997 to investigate the annually persistent occurrence of the spring peak of the chlorophyll α concentration in the >10μm size fraction immediately after the retreat of sea ice, as described by K. Hamasaki et al. (Plankton Biol. Ecol., 45,151,1998). Species composition of natural phytoplankton assemblages was also investigated to study whether phytoplankton or ice algae were responsible for the spring peak in the coastal water. The spring peak occurred immediately after the retreat of sea ice but timing of the occurrence was different between the stations occupied in the present study. The spatial heterogenity in occurrence of the spring peak seemed to be related to the sea ice distribution between the stations. New sea ice provided only a small supply of ice algae due to the relatively short growth period inside of the harbor. Large ice floes provided for a large supply of ice algae due to the long growth period outside of the harbor. The magnitude of the spring peak was related to sea ice growth. However, those ice algae seemed to sink to the bottom with little contribution to phytoplankton assemblage in the harbor, while ice algae contributed significantly to the spring peak outside of the harbor. Species composition revealed relatively fast response of phytoplankton to the environmental change after the disappearance of sea ice. Surface assemblages of phytoplankton including ice algae seemed to respond fully to the regional optical condition by changing in the species composition

The Effect of Microwave Sintering on the Microstructure and Properties of Calcium Phosphate Ceramic

AbstractDespite good ability to improved biological affinity and activity of calcium phosphate (CP) ceramic to the surrounding host tissue when implanted, CP ceramic is capable to encourage direct bond with bone as their chemical compositions are similar to the mineral phase of bone. However, the low mechanical property of CP ceramic restricts use in load-bearing applications. Therefore, the primary aim of this study was to fabricate dense CP ceramic via used of microwave sintering analyze the microstructure and mechanical properties comparison to conventional ceramic sintering. The sintered specimens were characterized by their surface microstructure, density measurement and hardness test. The result demonstrated that the density and hardness values of sintered CP ceramic specimens by microwave sintering were higher than conventional sintering. The microstructures of CP ceramic microwave sintered specimens show also better microstructures (analyzed by FESEM technique), with fines grain size and the present of apatite layer growth on the surface when examined with SBF solution. It can be concluded that the microwave sintering enhanced better microstructure and mechanical properties of CP ceramic

Physical and Histological Comparison of Hydroxyapatite, Carbonate Apatite, and β-Tricalcium Phosphate Bone Substitutes

Three commercially available artificial bone substitutes with different compositions, hydroxyapatite (HAp; Neobone®), carbonate apatite (CO3Ap; Cytrans®), and β-tricalcium phosphate (β-TCP; Cerasorb®), were compared with respect to their physical properties and tissue response to bone, using hybrid dogs. Both Neobone® (HAp) and Cerasorb® (β-TCP) were porous, whereas Cytrans® (CO3Ap) was dense. Crystallite size and specific surface area (SSA) of Neobone® (HAp), Cytrans® (CO3Ap), and Cerasorb® (β-TCP) were 75.4 ± 0.9 nm, 30.8 ± 0.8 nm, and 78.5 ± 7.5 nm, and 0.06 m2/g, 18.2 m2/g, and 1.0 m2/g, respectively. These values are consistent with the fact that both Neobone® (HAp) and Cerasorb® (β-TCP) are sintered ceramics, whereas Cytrans® (CO3Ap) is fabricated in aqueous solution. Dissolution in pH 5.3 solution mimicking Howship’s lacunae was fastest in CO3Ap (Cytrans®), whereas dissolution in pH 7.3 physiological solution was fastest in β-TCP (Cerasorb®). These results indicated that CO3Ap is stable under physiological conditions and is resorbed at Howship’s lacunae. Histological evaluation using hybrid dog mandible bone defect model revealed that new bone was formed from existing bone to the center of the bone defect when reconstructed with CO3Ap (Cytrans®) at week 4. The amount of bone increased at week 12, and resorption of the CO3Ap (Cytrans®) was confirmed. β-TCP (Cerasorb®) showed limited bone formation at week 4. However, a larger amount of bone was observed at week 12. Among these three bone substitutes, CO3Ap (Cytrans®) demonstrated the highest level of new bone formation. These results indicate the possibility that bone substitutes with compositions similar to that of bone may have properties similar to those of bone

Effects of acidic calcium phosphate concentration on setting reaction and tissue response to β-tricalcium phosphate granular cement

Beta-tricalcium phosphate granular cement (β-TCP GC), consisting of β-TCP granules and an acidic calcium phosphate (Ca-P) solution, shows promise in the reconstruction of bone defects as it sets to form interconnected porous structures, i.e., β-TCP granules are bridged with dicalcium phosphate dihydrate (DCPD) crystals. In this study, the effects of acidic Ca-P solution concentration (0–600 mmol/L) on the setting reaction and tissue response to β-TCP GC were investigated. The β-TCP GC set upon mixing with its liquid phase, based on the formation of DCPD crystals, which bridged β-TCP granules to one another. Diametral tensile strength of the set β-TCP GC was relatively the same, at approximately 0.6 MPa, when the Ca-P concentration was 20–600 mmol/L. Due to the setting ability, reconstruction of the rat’s calvarial bone defect using β-TCP GC with 20, 200, and 600 mmol/L Ca-P solution was much easier compared to that with β-TCP granules without setting ability. Four weeks after the reconstruction, the amount of new bone was the same, approximately 17% in both β-TCP GC and β-TCP granules groups. Cellular response to β-TCP granules and β-TCP GC using the 20 mmol/L acidic Ca-P solution was almost the same. However, β-TCP GC using the 200 and 600 mmol/L acidic Ca-P solution showed a more severe inflammatory reaction. It is concluded, therefore, that β-TCP GC, using the 20 mmol/L acidic Ca-P solution, is recommended as this concentration allows surgical techniques to be performed easily and provides good mechanical strength, and the similar cellular response to β-TCP granules

Histological comparison of three apatitic bone substitutes with different carbonate contents in alveolar bone defects in a beagle mandible with simultaneous implant installation

Since bone apatite is a carbonate apatite containing carbonate in an apatitic structure, carbonate content may be one of the factors governing the osteoconductivity of apatitic bone substitutes. The aim of this study was to evaluate the effects of carbonate content on the osteoconductivity of apatitic bone substitutes using three commercially available bone substitutes for the reconstruction of alveolar bone defects of a beagle mandible with simultaneous dental implant installation. NEOBONE®, Bio-Oss®, and Cytrans® that contain 0.1 mass%, 5.5 mass%, and 12.0 mass% of carbonate, respectively, were used in this study. The amount of newly formed bone in the upper portion of the alveolar bone defect of the beagle’s mandible was 0.7%, 6.6%, and 39.4% at 4 weeks after surgery and 4.7%, 39.5% and 75.2% at 12 weeks after surgery for NEOBONE®, Bio-Oss®, and Cytrans®, respectively. The results indicate that bone-to-implant contact ratio was the largest for Cytrans®. Additionally, the continuity of the alveolar ridge was restored in the case of Cytrans®, whereas the continuity of the alveolar ridge was not sufficient when using NEOBONE® and Bio-Oss®. Both Cytrans® and Bio-Oss® that has a relatively larger carbonate content in their apatitic structure was resorbed with time. We concluded that carbonate content is one of important factors governing the osteoconductivity of apatitic bone substitutes

Fabrication and Physical Evaluation of Gelatin-Coated Carbonate Apatite Foam

Carbonate apatite (CO3Ap) foam has gained much attention in recent years because of its ability to rapidly replace bone. However, its mechanical strength is extremely low for clinical use. In this study, to understand the potential of gelatin-reinforced CO3Ap foam for bone replacement, CO3Ap foam was reinforced with gelatin and the resulting physical characteristics were evaluated. The mechanical strength increased significantly with the gelatin reinforcement. The compressive strength of gelatin-free CO3Ap foam was 74 kPa whereas that of the gelatin-reinforced CO3Ap foam, fabricated using 30 mass % gelatin solution, was approximately 3 MPa. Heat treatment for crosslinking gelatin had little effect on the mechanical strength of the foam. The gelatin-reinforced foam did not maintain its shape when immersed in a saline solution as this promoted swelling of the gelatin; however, in the same conditions, the heat-treated gelatin-reinforced foam proved to be stable. It is concluded, therefore, that heat treatment is the key to the fabrication of stable gelatin-reinforced CO3Ap foam

マイクロファイバーを用いた多孔質炭酸アパタイト顆粒の開発とウサギ頭蓋骨における組織学的評価

Carbonate apatite (CO3Ap) granules are known to show good osteoconductivity and replaced to new bone. On the other hand, it is well known that a porous structure allows bone tissue to penetrate its pores, and the optimal pore size for bone ingrowth is dependent on the composition and structure of the scaffold material. Therefore, the aim of this study was to fabricate various porous CO3Ap granules through a two-step dissolution-precipitation reaction using CaSO4 as a precursor and 30-, 50-, 120-, and 205-μm diameter microfibers as porogen and to find the optimal pore size of CO3Ap. Porous CO3Ap granules were successfully fabricated with pore size 8.2-18.7% smaller than the size of the original fiber porogen. Two weeks after the reconstruction of rabbit calvarial bone defects using porous CO3Ap granules, the largest amount of mature bone was seen to be formed inside the pores of CO3Ap (120) [porous CO3Ap granules made using 120-μm microfiber] followed by CO3Ap (50) and CO3Ap (30). At 4 and 8 weeks, no statistically significant difference was observed based on the pore size, even though largest amount of mature bone was formed in case of CO3Ap (120). It is concluded, therefore, that the optimal pore size of the CO3Ap is that of CO3Ap (120), which is 85 μm