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Bone grafting is crucial for bone regeneration. Recent studies have proposed the use of calcium citrate (CC) as a potential graft material. Notably, citrate does not inhibit hydroxyapatite (HAp) formation at specific calcium-to-citrate molar ratios. Octacalcium phosphate (OCP)/gelatine (Gel) composites, which are commonly produced from porcine Gel, are valued for their biodegradability and bone replacement capability. This study introduces fish Gel as an alternative to porcine Gel because of its wide acceptance and eco-friendliness. This is the first study to examine the interaction effects between two osteogenic materials, OCP/CC, and the influence of different gelatine matrix components on HAp formation in an SBF. Samples with varying CC contents were immersed in an SBF for 7 d and analysed using various techniques, confirming that high CC doses prevent HAp formation, whereas lower doses facilitate it. Notably, small-sized OCP/CC/porcine Gel composites exhibit a high HAp generation rate. Porcine Gel composites form denser HAp clusters, whereas fish Gel composites form larger spherical HAps. This suggests that lower CC doses not only avoid inhibiting HAp formation but also enhance it with the OCP/Gel composite. Compared with porcine Gel, fish Gel composites show less nucleation but an increased crystal growth for HAp. [ABSTRACT FROM AUTHOR]

Porcine collagen is widely used in regenerative therapies to generate membranes for bone augmentation. However, porcine or bovine gelatin or collagen is often not appropriate for patients with creed and religious beliefs or for allergic reasons. In this study, we evaluated the potential of fish gelatin to generate membranes. Fish gelatin and hydroxyapatite (HAp) were used at three different ratios (2:0, 2:1, 2:1.5, and 2:2) to prepare gelatin-hydroxyapatite (G-HAp) membranes via freeze-drying and heat-crosslinking. The surface morphology and cell attachment of G-HAp membranes were observed using scanning electron microscopy and confocal laser microscopy. G-HAp membrane was placed at the bottom of a well plate, and MC3T3-E1 cells were seeded on it. Cell viability and cytotoxicity were tested after 1 and 3 days of culture. Alkaline phosphatase (ALP) and alizarin red staining was performed at 10 and 21 days, respectively. Viability of cells on G-HAp membrane with the gelatin:HAp ratio of 2:1.5 was significantly higher than that on membranes with other gelatin:HAp ratios. ALP and alizarin red staining showed that ALP-positive areas and calcium deposition were the highest on G-HAp membrane with the gelatin:HAp ratio of 2:1. These membranes showed negligible cytotoxicity. Fish-derived G-HAp membranes have the potential to promote osteogenic differentiation of MC3T3-E1 cells with negligible cytotoxicity. [ABSTRACT FROM AUTHOR]

Improving the damage tolerance and reliability of ceramic artificial bone materials, such as sintered bodies of hydroxyapatite (HAp), that remain in vivo for long periods of time is of utmost importance. However, the intrinsic brittleness and low damage tolerance of ceramics make this challenging. This paper reports the synthesis of highly damage tolerant calcium phosphate-based materials with a bioinspired design for novel artificial bones. The heat treatment of isophthalate ion-containing octacalcium phosphate compacts in a nitrogen atmosphere at 1000°C for 24 h produced an HAp/β-tricalcium phosphate/pyrolytic carbon composite with a brick-and-mortar structure (similar to that of the nacreous layer). This composite exhibited excellent damage tolerance, with no brittle fracture upon nailing, likely attributable to the specific mechanical properties derived from its unique microstructure. Its maximum bending stress, maximum bending strain, Young's modulus, and Vickers hardness were 11.7 MPa, 2.8 × 10‒2, 5.3 GPa, and 11.7 kgf/mm2, respectively. The material exhibited a lower Young's modulus and higher fracture strain than that of HAp-sintered bodies and sintered-body samples prepared from pure octacalcium phosphate compacts. Additionally, the apatite-forming ability of the obtained material was confirmed in vitro, using a simulated body fluid. The proposed bioinspired material design could enable the fabrication of highly damage tolerant artificial bones that remain in vivo for long durations of time. Synthesis of hydroxyapatite/β-tricalcium phosphate/pyrolytic carbon composites with excellent damage tolerance as promising new artificial-bone materials. [ABSTRACT FROM AUTHOR]

Octacalcium phosphate (OCP; Ca8(HPO4)2(PO4)4 ∙ 5H2O) is a precursor of hydroxyapatite found in human bones and teeth, and is among the inorganic substances critical for hard tissue formation and regeneration in the human body. OCP has a layered structure and can incorporate carboxylate ions into its interlayers. However, studies involving the incorporation of tetracarboxylic and multivalent (pentavalent and above) carboxylic acids into OCP have not yet been reported. In this study, we investigate the incorporation of pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid), a type of tetracarboxylic acid, into OCP. We established that pyromellitate ions could be incorporated into OCP by a wet chemical method using an acetate buffer solution containing pyromellitic acid. The derived OCP showed a brilliant blue emission under UV light owing to the incorporated pyromellitate ions. Incorporation of a carboxylic acid into OCP imparted new functions, which could enable the development of novel functional materials for biomedical applications. Octacalcium phosphate is a precursor to a key component of human bone and tooth enamel which can incorporate carboxylate species, but the effect of multivalent carboxylates is not well understood. Here the incorporation of tetracarboxylic acids into OCP is shown to influence the structural and optical properties of the resultant composite. [ABSTRACT FROM AUTHOR]

Initial cellular responses following implantation are important for inducing osteoconduction. We investigated cell adhesion, spreading, proliferation and differentiation of mouse MC3T3-E1 osteoblastic cells on untreated or fibronectin (Fn)-coated discs of hydroxyapatite (HAp) or alpha-type alumina (α-Al 2 O 3 ). Fn coating significantly enhanced adhesion and spreading of MC3T3-E1 cells on HAp, but did not affect MC3T3-E1 cell proliferation and differentiation on HAp or α-Al 2 O 3 . Fn-coated HAp likely does not stimulate pre-osteoblast cells to initiate the process of osteoconduction; however, Fn adsorption might affect the response of inflammatory cells to the implanted material or, in conjunction with other serum proteins, stimulate pre-osteoblast cell proliferation and differentiation. Further studies on the effect of serum proteins in cell culture and the efficacy of Fn-coated HAp and α-Al 2 O 3 in vivo are warranted. [ABSTRACT FROM AUTHOR]

Initial cell responses following implantation are important for inducing osteoconductivity. We investigated cell adhesion, spreading, and proliferation in response to native and bovine serum albumin (BSA)-adsorbed disc of hydroxyapatite (HA) or alpha-type alumina (α-Al2O3) using mouse MC3T3-E1 osteoblastic cells and mouse RAW264.7 macrophages. The adsorbed BSA inhibited adhesion and spreading of MC3T3-E1 cells, but did not affect MC3T3-E1 cell proliferation on HA and α-Al2O3 substrates. Thus, MC3T3-E1 cells quickly adhere to original HA before cell binding is impeded by adsorption of BSA in quantities sufficient to inhibit the adhesion of MC3T3-E1 cells. The adsorbed BSA inhibits adhesion of RAW264.7 cells to α-Al2O3, but not to HA. BSA adsorption does not affect RAW264.7 cell spreading and proliferation on both HA and α-Al2O3 substrates. Thus, BSA adsorbed on HA stimulates a different cell response than α-Al2O3. Moreover, quick adherence of osteoblast cells and monocyte-macrophage lineage cells plays a role in HA osteoconductivity. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 1880-1886, 2014. [ABSTRACT FROM AUTHOR]

Bone cement containing alumina particles with a specific crystalline structure exhibits the ability to bond with bone. These particles (AL-P) are mainly composed of delta-type alumina (δ-AlO). It is likely that some of the proteins present in the body environment are adsorbed onto the cement and influence the expression of its bioactivity. However, the effect that this adsorption of proteins has on the bone-bonding mechanism of bone cement has not yet been elucidated. In this study, we investigated the characteristics of the adsorption of bovine serum albumin (BSA) onto AL-P and compared them with those of its adsorption onto hydroxyapatite (HA), which also exhibits bone-bonding ability, as well as with those of adsorption onto alpha-type alumina (α-AlO), which does not bond with bone. The adsorption characteristics of BSA onto AL-P were very different from those onto α-AlO but quite similar to those onto HA. It is speculated that BSA is adsorbed onto AL-P and HA by interionic interactions, while it is adsorbed onto α-AlO by electrostatic attraction. The results suggest that the specific adsorption of albumin onto implant materials might play a role in the expression of the bone-bonding abilities of the materials. [ABSTRACT FROM AUTHOR]

In present study, a new composition of glass-ceramic was synthesized based on the Na2O-CaO-SiO2-P2O5 glass system. Heat treatment of glass powder was carried out in 2 stages: 600°C as the nucleation temperature and different temperature on crystallization at 850, 950 and 1000°C. The glass-ceramic heat-treated at 950°C was selected as bioactive filler in commercial PMMA bone cement; (PALACOS® LV) due to its ability to form 2 high crystallization phases in comparison with 850 and 1000°C. The results of this newly glass-ceramic filled PMMA bone cement at 0-16 wt% of filler loading were compared with those of hydroxyapatite (HA). The effect of different filler loading on the setting properties was evaluated. The peak temperature during the polymerization of bone cement decreased when the liquid to powder (L/P) ratio was reduced. The setting time, however, did not show any trend when filler loading was increased. In contrast, dough time was observed to decrease with increased filler loading. Apatite morphology was observed on the surface of the glass-ceramic and selected cement after bioactivity test. [ABSTRACT FROM AUTHOR]

Abstract: Calcium phosphate crystals were synthesized in polyacrylamide (PAAm) hydrogel, and the effects of the concentrations of calcium and phosphate ions on the crystalline phases and morphology were investigated. PAAm hydrogels containing diammonium hydrogen phosphate ((NH4)2HPO4) were transformed into calcified materials by diffusion of calcium ions from calcium nitrate (Ca(NO3)2) aqueous solution into the gels. Several kinds of calcium phosphate crystals were precipitated at various Ca(NO3)2 concentrations (0.5–4.0mol·dm−3), or (NH4)2HPO4 contents (3.6–21.6mmol) in the gels. The crystalline phases were mainly determined by the (NH4)2HPO4 content in the gels. When the (NH4)2HPO4 content was ≥10.8mmol, hydroxyapatite (HAp) formed near the interfaces between Ca(NO3)2 solution and the gels, whereas octacalcium phosphate (OCP) formed in gels with ≤10.8mmol (NH4)2HPO4. HAp crystals were granular in form and about 200nm in diameter, and OCP crystals were spherulitic with diameter 10–70μm. [Copyright &y& Elsevier]

Calcium phosphate crystals were synthesized by diffusing calcium ions into silica hydrogels containing phosphate ions. Hydroxyapatite [HAp, Ca10(PO4)6(OH)2] and octacalcium phosphate [OCP, Ca8(HPO4)2(PO4)4.5H2O] with different types of crystal morphology were formed in the gel. The HAp had an irregular or rod shape, a few micrometers in length, while the OCP had an irregular, spherulite, rod- or ribbonlike shape, ranging in size from a few micrometers to several tens of micrometers, depending on the amount of phosphoric acid added and the reaction temperature. The morphology of the OCP changed from an irregular shape to a ribbonlike or rod shape, via a spherulite shape, depending on the amount of phosphoric acid added and the reaction temperature. The degree of supersaturation of the reaction environment and the rate-determining step in the HAp and OCP crystal growth mechanism have been ascribed to the changes in crystal morphology of the HAp and OCP. [ABSTRACT FROM AUTHOR]

Carbonate-containing hydroxyapatite (CO 3 -HAp) shows higher osteoconductivity than pure hydroxyapatite but the underlying mechanism is unclear. As specific adsorption of proteins on CO 3 -HAp may affect cellular responses and osteoconductivity, we examined the contribution of protein adsorption to the high osteoconductivity observed with CO 3 -HAp. We prepared CO 3 -HAp powders with different carbonate contents (0.3, 4.8, or 8.3 wt%) and investigated the adsorption behaviour of fibronectin (Fn) on the powders. We found that the Fn adsorption capacity of CO 3 -HAp decreased with increasing carbonate content. Although the Hill or Langmuir isotherm was the best-fit for the adsorption of Fn onto CO 3 -HAp with a carbonate content of 0.3 or 4.8 wt%, the Brunauer–Emmett–Teller isotherm was the best-fit for Fn adsorption on CO 3 -HAp with an 8.3 wt% carbonate content. These results show that the carbonate content of CO 3 -HAp influences the adsorption behaviour of Fn and suggest that its specific adsorption contributes to the high osteoconductivity of CO 3 -HAp. The findings do not affect the clinical application of CO 3 -HAp directly, but they might lead to the development of bone substitutes with high osteoconductivity. [ABSTRACT FROM AUTHOR]