Low Crystalline Apatite Research Articles

Bioactive Non-Woven Silica Fabric Made Through Electro-Spinning Method

Non-woven silica fabric was made by electro-spinning method for the application as a bone grafting material. The silica gel, the source material for electro-spinning, was prepared by the hydrolysis of tetraethyl orthosilicate in the presence of water, hydrochloric acid and ethanol. It was transferred to a syringe (spinneret), which was connected to the high voltage supply generating a high electric field between the spinneret and the ground collecting drum. The silica fibers were spun under the electric field of 2 KV/cm. Their diameters were in the range from about 100 nm to 5 µm. After soaking in the SBF for 4 week, low crystalline apatite crystals were observed to occur partly on their surfaces. From the results, it can be concluded that the non-woven silica fabric made by electro-spinning method has the apatite forming ability in the SBF and it means it has a potential to be used as a bone grafting material because of its apatite-forming ability, high surface area to volume ratio and high porosity.

Fabrication of Biporous Low-crystalline Apatite Based on Mannitol Dissolution from Apatite Cement

Biporous (macro- and microporous) calcium phosphate gains much attention as a bone substitute material because of its large surface area and that it improves cell penetration. In the present study, we evaluated the feasibility of biporous, low-crystalline apatite based on dissolution of mannitol from self-setting apatite cement (Biopex). Mannitol--known as a biocompatible, easily dissolved monosaccharide alcohol--was recrystallized to obtain larger crystals. It was crushed with pestle and mortar, sieved to obtain crystals which passed through a 500-microm mesh but which remained against a 300-microm mesh, and then used as porogen. Although Biopex containing 60 wt% mannitol was not able to be taken out of the mold, addition of mannitol caused no initial setting inhibition to Biopex if the amount was 40 wt% or less. Similarly, transformation to apatitic product was confirmed when the apatite cement was immersed in 0.9% saline kept at 37 degrees C for seven days. The set mass became low-crystalline, biporous apatite with approximately 60% porosity.

Hydrolysis and cytocompatibility of zinc-containing α-tricalcium phosphate powder

Zinc is an essential trace element with stimulatory effects on bone formation in vitro and in vivo. In order to apply zinc-containing α-tricalcium phosphate (αZnTCP) to αTCP-based calcium phosphate cement, αZnTCP powders containing various amounts of zinc were prepared and the optimum zinc content was examined from the viewpoints of hydrolysis property and cytocompatibility. Single-phase αZnTCP containing zinc from 0.00 to 1.26 wt.% was obtained by heating zinc-containing β-tricalcium phosphate at 1450 °C. At a zinc content of 0.11 wt.%, there was no significant difference in the amount of calcium-deficient low-crystalline apatite formed by hydrolysis between pure αTCP and αZnTCP. The hydrolysis of αZnTCP was significantly retarded by incorporating zinc at or more than 0.26 wt.% due to the inhibitory effect of zinc on the crystal growth of apatite. The MC3T3-E1 cell densities cultured with pure αTCP and 0.11 Zn wt.% αZnTCP powders showed no significant difference in the range of powder dose from 10 to 1000 μg mL −1. The result indicated that the cytocompatibility of pure αTCP powder was comparable to that of αZnTCP at the zinc content of 0.11 wt.%. Therefore, the optimum zinc content of αZnTCP powder is less than 0.26 wt.%, and preferably at or less than 0.11 wt.% to apply to an αTCP-based calcium phosphate cement.

The interaction between osteoclast-like cells and osteoblasts mediated by nanophase calcium phosphate-hybridized tendons

We developed a novel technique of hybridizing calcium phosphate (CaP) with bioorganic soft tissue using an alternating soaking process. By this technique, we hybridized CaP with a grafted tendon tissue to bond with a bone tunnel. Tendons were soaked in Ca and NaHPO 4 solutions alternately for 10 min. Needle-like CaP crystals 30–50 nm in length including low-crystalline apatite were deposited on and between collagen fibrils from the surface to 200 μm deep in the tendon. In light and transmission electron microscopic images, osteoclast-like cells and osteoblasts appeared on the implanted tendon and osteoid was observed on the tendon surface at 1 week postoperatively. At 2 weeks postoperatively, osteoclast-like cells resolved the tendon by forming Howship's lacuna-like spaces on the surfaces and osteoblasts formed osteoid in these spaces. Direct bonding between the implanted tendon and the newly formed bone was observed. At 3 weeks postoperatively, thick newly formed bone firmly bonded to tendon surface. From these results, we conclude that the tendons prepared by an accelerated CaP hybridization method efficiently enhance osteoclast-like cells and osteoblasts to bond the implanted tendons to newly formed bone.

The interaction between osteoclast-like cells and osteoblasts mediated by nanophase calcium phosphate-hybridized tendons

We developed a novel technique of hybridizing calcium phosphate (CaP) with bioorganic soft tissue using an alternating soaking process. By this technique, we hybridized CaP with a grafted tendon tissue to bond with a bone tunnel. Tendons were soaked in Ca and NaHPO 4 solutions alternately for 10 min. Needle-like CaP crystals 30–50 nm in length including low-crystalline apatite were deposited on and between collagen fibrils from the surface to 200 μm deep in the tendon. In light and transmission electron microscopic images, osteoclast-like cells and osteoblasts appeared on the implanted tendon and osteoid was observed on the tendon surface at 1 week postoperatively. At 2 weeks postoperatively, osteoclast-like cells resolved the tendon by forming Howship's lacuna-like spaces on the surfaces and osteoblasts formed osteoid in these spaces. Direct bonding between the implanted tendon and the newly formed bone was observed. At 3 weeks postoperatively, thick newly formed bone firmly bonded to tendon surface. From these results, we conclude that the tendons prepared by an accelerated CaP hybridization method efficiently enhance osteoclast-like cells and osteoblasts to bond the implanted tendons to newly formed bone.

Preparation of a bioactive and degradable poly( ε-caprolactone)/silica hybrid through a sol–gel method

A bioactive and degradable poly( ε-caprolactone)/silica hybrid was synthesized for the application as a bone substitute. Triethoxysilane end capped poly( ε-caprolactone) was prepared by the reaction with α, ω-hydroxyl poly( ε-caprolactone) and 3-isocyanatopropyl triethoxysilane using 1,4-diazabicyclo[2,2,2,]octane as a catalyst. It was then co-condensed with tetraethyl orthosilicate and calcium nitrate tetrahydrate via a sol–gel method. The bioactivity of the poly( ε-caprolactone)/silica hybrid was assessed using simulated body fluid and low crystalline apatite was successfully formed on its surface after soaking for 1 week at 36.5°C. Its biodegradability was evaluated in the phosphate buffered saline and the degradability was mostly come from the poly( ε-caprolactone) phase in the hybrid. It means that this hybrid is likely to be applicable to a bioactive and degradable bone substitute.

Preparation of a Bioactive Poly(methyl methacrylate)/Silica Nanocomposite

The nanocomposite of a poly(methyl methacrylate)/silica containing calcium salt was synthesized through the sol–gel method. Methyl methacrylate was co‐polymerized with 3‐(trimethoxysilyl)propyl methacrylate and then co‐condensed with tetraethyl orthosilicate and calcium nitrate tetrahydrate. Low crystalline hydroxycarbonate apatite was successfully formed on the surface after soaking in simulated body fluid for 1 week at 36.5°C. This study demonstrates that this nanocomposite may be used as a bioactive bone substitute or filler for poly(methyl methacrylate) bone cement.