Fabrication of novel bone haemostasis sheet by using sugar-containing hydroxyapatite and plant-derived polymer.

The fabrication conditions of bone-haemostasis sheet were examined by using (i) phosphoryl oligosaccharides of calcium (POs-Ca), sugar-containing hydroxyapatite (s-Ca10(PO4)6(OH)2: s-HAp) derived from POs-Ca and (ii) natural plant-derived polymers (locust bean gum (LBG), guar gum (GG) and alginate (AG)). The sol, which had been prepared by dissolving 2 mass% LBG/GG and 2 mass% AG into 200 cm3 deionized water and then by agitating at the speed of 20 000 r.p.m., was immersed into 3 mass% POs-Ca solution at room temperature for 24 h; it was hydrothermally treated at 100°C for 5 h, and then freeze-dried at -50°C for 24 h to form porous composite sheet. The microscopic observation showed that the pore sizes were controlled in the range of 5-100 µm by the optimization of LBG/GG ratio. The composite sheet showed the noted uptake of simulated body fluid (1426%) at 37.0°C and also the human blood. Thus, the porous composite sheet was found to be a promising candidate of the bone haemostasis, on the basis of the data of haemostasis, uptake ability of SBF and solubility in acetic acid-sodium acetate buffer solution.

Calcium-mediated secondary cross-linking of bisphosphonated oligo(poly(ethylene glycol) fumarate) hydrogels.

This study demonstrates, for the first time, that synthetic PEG-based hydrogels can be cross-linked reversibly by calcium upon functionalization of the polymer backbone with bisphosphonate groups (BPs) that allow for the formation of strong coordination bonds with divalent metal ions such as Mg(2+) and Ca(2+). More specifically, it is shown that BP-functionalized hydrogels can be shaped by providing calcium ions as reversible physical cross-linkers.

Influence of the pore generator on the evolution of the mechanical properties and the porosity and interconnectivity of a calcium phosphate cement.

Porosity and interconnectivity are important properties of calcium phosphate cements (CPCs) and bone-replacement materials. Porosity of CPCs can be achieved by adding polymeric biodegradable pore-generating particles (porogens), which can add porosity to the CPC and can also be used as a drug-delivery system. Porosity affects the mechanical properties of CPCs, and hence is of relevance for clinical application of these cements. The current study focused on the effect of combinations of polymeric mesoporous porogens on the properties of a CPC, such as specific surface area, porosity and interconnectivity and the development of mechanical properties. CPC powder was mixed with different amounts of PLGA porogens of various molecular weights and porogen sizes. The major factors affecting the properties of the CPC were related to the amount of porogen loaded and the porogen size; the molecular weight did not show a significant effect per se. A minimal porogen size of 40 µm in 30 wt.% seems to produce a CPC with mechanical properties, porosity and interconnectivity suitable for clinical applications. The properties studied here, and induced by the porogen and CPC, can be used as a guide to evoke a specific host-response to maintain CPC integrity and to generate an explicit bone ingrowth.

Effects of blood on bone cement made of calcium phosphate: problems and advantages.

In recent years, calcium phosphate cements (CPCs) have frequently been used as bone substitutes in the field of orthopedic surgery. When CPC is used as a bone substitute in vivo, blood contamination is unavoidable. To date, however, no detailed study has been conducted focusing on how the physical properties of CPCs would change under the influence of blood. In this study, the effects of blood contamination on Biopex-R (BPR, PENTAX, Tokyo) are examined in vitro and in vivo. The compressive strength of BPR after setting decreased depending on the amount of contaminating blood. The BPR, which has set in vivo, not only has a fragile surface due to the contamination by blood, but also has a propensity to shorten and be destroyed during the early postoperative stage, especially in the bone exposed to loads. On the other hand, radiographic and histological features in vivo indicated that the absorption and the bone replacement of BPR were stimulated by blood contamination. In the clinical evaluation, the patient's own peripheral venous blood was added to the BPR. One year after the surgery, the absorption was noted around the hardened BPR. To advance CPCs (including BPR) as bioabsorbable bone replaceable materials, it is essential to utilize the patient's own blood in combination with the CPC.

Effect of metal-oxide addition on the sintering of beta-calcium orthophosphate.

The effect of metal-oxide addition (1 approximately 10 mol %) on the sintering of beta-calcium orthophosphate (beta-Ca(3)(PO(4))(2)) was examined by pressureless sintering at 1070 degrees C for 5 h. The metal-oxide additives used were as follows: (i) monovalent metal-oxides, Li(2)O, Na(2)O, and K(2)O; (ii) divalent metal-oxides, MgO, CaO, SrO, and BaO; (iii) trivalent metal-oxides, Al(2)O(3) and Fe(2)O(3); and (iv) tetravalent metal-oxides, SiO(2), TiO(2), and ZrO(2). The relative densities of the sintered beta-Ca(3)(PO(4))(2) compacts were reduced with increasing amounts of monovalent and divalent metal-oxide additions, except for the case of MgO addition when the relative density remained with increasing amount of MgO up to 4 mol %. In the case of trivalent metal-oxide additions, the relative density of sintered beta-Ca(3)(PO(4))(2) compact was reduced with increasing amount of Al(2)O(3) addition, whereas it was enhanced with increasing amount of Fe(2)O(3) addition and reached 98.7% at 10 mol % Fe(2)O(3) addition. In the case of tetravalent metal-oxide additions, relative densities of the sintered beta-Ca(3)(PO(4))(2) compacts were slightly reduced with increasing amounts of SiO(2) and ZrO(2) additions, whereas no appreciable changes in the relative density were observed with increasing amount of TiO(2) addition.