How useful is SBF in predicting in vivo bone bioactivity

Ceramics used for the repair and reconstruction of diseased or damaged parts of the musculo-skeletal system, termed bioceramics, may be bioinert (alumina, zirconia), resorbable (tricalcium phosphate), bioactive (hydroxyapatite, bioactive glasses, and glass-ceramics), or porous for tissue ingrowth (hydroxyapatite-coated metals, alumina). Applications include replacements for hips, knees, teeth, tendons, and ligaments and repair for periodontal disease, maxillofacial reconstruction, augmentation and stabilization of the jaw bone, spinal fusion, and bone fillers after tumor surgery. Carbon coatings are thromboresistant and are used for prosthetic heart valves. The mechanisms of tissue bonding to bioactive ceramics are beginning to be understood, which can result in the molecular design of bioceramics for interfacial bonding with hard and soft tissues. Composites are being developed with high toughness and elastic modulus match with bone. Therapeutic treatment of cancer has been achieved by localized delivery of radioactive isotopes via glass beads. Development of standard test methods for prediction of long-term (20-year) mechanical reliability under load is still needed.

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Bioceramics: From Concept to Clinic

Bioceramics : from concept to clinic

High-strength bioactive glass-ceramic A-W was soaked in various acellular aqueous solutions different in ion concentrations and pH. After soaking for 7 and 30 days, surface structural changes of the glass-ceramic were investigated by means of Fourier transform infrared reflection spectroscopy, thin-film x-ray diffraction, and scanning electronmicroscopic observations, in comparison with in vivo surface structural changes. So-called Tris buffer solution, pure water buffered with trishydroxymethyl-aminomethane, which had been used by various workers as a "simulated body fluid," did not reproduce the in vivo surface structural changes, i.e., apatite formation on the surface. A solution, ion concentrations and pH of which are almost equal to those of the human blood plasma--i.e., Na+ 142.0, K+ 5.0, Mg2+ 1.5, Ca2+ 2.5, Cl- 148.8, HCO3- 4.2 and PO4(2-) 1.0 mM and buffered at pH 7.25 with the trishydroxymethyl-aminomethane--most precisely reproduced in vivo surface structure change. This shows that careful selection of simulated body fluid is required for in vitro experiments. The results also support the concept that the apatite phase on the surface of glass-ceramic A-W is formed by a chemical reaction of the glass-ceramic with the Ca2+, HPO4(2-), and OH- ions in the body fluid.

Solutions able to reproduce in vivo surface-structure changes in bioactive glass-ceramic A-W.

Titanium and titanium alloys are widely used in biomedical devices and components, especially as hard tissue replacements as well as in cardiac and cardiovascular applications, because of their desirable properties, such as relatively low modulus, good fatigue strength, formability, machinability, corrosion resistance, and biocompatibility. However, titanium and its alloys cannot meet all of the clinical requirements. Therefore, in order to improve the biological, chemical, and mechanical properties, surface modification is often performed. This article reviews the various surface modification technologies pertaining to titanium and titanium alloys including mechanical treatment, thermal spraying, sol–gel, chemical and electrochemical treatment, and ion implantation from the perspective of biomedical engineering. Recent work has shown that the wear resistance, corrosion resistance, and biological properties of titanium and titanium alloys can be improved selectively using the appropriate surface treatment techniques while the desirable bulk attributes of the materials are retained. The proper surface treatment expands the use of titanium and titanium alloys in the biomedical fields. Some of the recent applications are also discussed in this paper.

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Surface modification of titanium, titanium alloys, and related materials for biomedical applications

Verfahren zur herstellung von glasfilmen unter verwendung einer silizium-alkoxid enthaltenden loesung

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Preparation of Ag/TiO₂ Composite Films by the Sol-Gel Method (Commemoration Issue Dedicated to Professor Sumio Sakka On the Occasion of His Retirement)

ゾル-ゲ ル法1)~4)は溶液か ら低 温で各種 の材料 を合成 する方法で,現 在,先 端材料分野で広 く注 目を集 めて い る.こ の方法で は,主 として金属の アルコキシ ド,ア セ チルアセ トナ ト,カ ルボ ン酸塩の ような金属有機化合物 や金属硝酸塩の ような無機化合物の溶液 をつ くり,こ れ らの化合物の加水分解重 合によって分子 クラス ターや微 細 な粒子の分散 した ゾルに変 え,さ らに反応 を進 ませて ゲル とす る。ゲル として固化する際に,バ ルク(板 やロ ッ ド),繊 維,コ ーテ ィング膜の よ うな形 をもつ材料 につ くりあげ るのが ゾル-ゲル法の特徴であ るが,粉 末 ある いは粒体 として利用するこ ともある。 また,ゲ ルの状態 で使用 する材料利用法が しだいに新材料の合成法 として 盛んにな りつつある.し か し形 のある ゲル を加熱 して形 のある ガラス またはセ ラ ミックスをつ くる ことはゾルゲル法 の最 も重要な応用分野 である. ゾル-ゲ ル法 では,バ ル ク,繊 維,コ ー ティング膜 を 直接つ くる場合 も,ゾ ル-ゲ ル法でつ くった粉末 を焼結 原料 として使用する場合 も,結 晶性の酸化物や炭酸塩 の 原料 を利用する従来の方法に くらべて数百 °C ~1000°C も低い温度 で目的物 をつ くる ことがで きる.こ のため,' 従来の方法 ではで きない化合物 を新 しく合成する ことが で きる.ま た,従 来の方法ではで きない形状の材料,た とえば,セ ラ ミックスの繊維 やコーテ ィング膜 を比較的 容易につ くるこ とがで きる.さ らに,場 合 によっては高 い生産性 を期待す ることがで きる. 本報告では,ゾ ル-ゲ ル法の概略 を示 し,バ ルク,繊 維, コー テ ィング膜 の直接 合成 について述べ る。 と くに ゾ ル-ゲ ル法の コーテ ィング膜作製へ の応用 について詳 し く解説する.

Sol-Gel Method and Its Applications

lattice constants, oxygen content and microstructure were examined. Sr could be substituted for 20% of Ba in YBa2Cu4Os and the lattice constants a, b and c decreased monotonically with increasing Sr concentration. T, (onset) and T, (end) of YBai .aSro.2Cu4O8 were 3 K higher and 2 K higher than those of YBa2Cu4Os, respectively. K could be substituted for 10% of Ba and the lattice constant a slightly decreased with increasing K concentration, whereas b and c remained constant. T, of YBa2_,KXu4Os_8 was slightly lower than that of YBa2Cu4O8. Na could be substituted for 5% of Ba and the lattice constant a decreased with increasing Na concentration, whereas b and c remained constant. T, (end) of YBa2_.,Na,Cu4Os_s was 4 K higher than that of YBa2Cu4O8. Grain growth was observed in the K- and Na-substituted samples. Changes of 7', by the substitution were discussed in terms of the contraction of the lattice, the formation of oxygen vacancies, the concentration of holes and the role of grain boundaries.

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Effects of Substitution of Sr, K or Na for Ba on the Structure and Properties of Gel-Derived YBa2Cu4O8 Superconducting Oxide

http://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433/77052/1/chd061_5-6_376.pdf

Sumio Sakka

Papers

Verfahren zur herstellung von glasfilmen unter verwendung einer silizium-alkoxid enthaltenden loesung

Preparation of Ag/TiO₂ Composite Films by the Sol-Gel Method (Commemoration Issue Dedicated to Professor Sumio Sakka On the Occasion of His Retirement)

Sol-Gel Method and Its Applications

Effects of Substitution of Sr, K or Na for Ba on the Structure and Properties of Gel-Derived YBa2Cu4O8 Superconducting Oxide

Low Temperature Preparation of Oxide Glasses and Ceramics from Metal Alkoxide Solutions