Abstract: Hydroxycarbonate apatite (HCA), which formed on a poly(lactic acid) (PLA) composite membrane containing vaterite or calcium chloride after soaking in simulated body fluid, was examined to clarify the importance of the ceramic phases in the composites. FT-IR spectra showed that the ratio of CO3/PO4 in the infrared adsorption bands of HCA formed on the PLA composite containing vaterite was much larger than that of HCA formed on the PLA composite containing
calcium chloride. Substitution of carbonate ion in hydroxyapatite is believed to be strongly influenced by ceramic phases in the composites. The zeta potentials of HCA formed on the PLA composite containing vaterite or calcium chloride was -6 mV or -17 mV, respectively. The zeta potential may be influenced by the amount of carbonate ion in hydroxyapatite.
Abstract: Bioactive glass scaffolds with interconnected macroporous networks have been
developed by foaming sol-gel derived bioactive glass of the 70S30C (70 mol% SiO2, 30 mol% CaO) composition. The effect of sintering temperature on the dissolution of the scaffolds in simulated body fluid (SBF) was investigated in 3D using x-ray micro-computer tomography (micro CT) and inductive coupled plasma (ICP) analysis. Micro-CT is non-destructive and allows observation of specific parts of the scaffold at various stages of degradation. However, data analysis is complex at present. Percentage porosity data obtained by micro-CT was compared to physical data and pore size distributions obtained from mercury intrusion porosimetry were compared to the interconnected pore diameters observed from the micro CT images.
Abstract: Dense, polycrystalline, synthetic hydroxyapatite (HA) was incubated for 36 days in modified simulated body fluid (SBF) with increased HCO3
- and reduced Cl- ion concentrations (27 and 120 mM, respectively) closer to actual blood plasma than typical SBF. The resulting precipitated apatite layer was characterized by X-ray photoelectron spectroscopy (XPS) and contact angle measurements and found to be nonstoichiometric, calcium deficient (Ca/P~1.06),
non-carbonate containing, and of intermediate hydrophilicity (advancing contact angle, qa=76.5±1.3°). The nanoscale surface topography of the SBF-incubated HA sample was imaged by tapping mode atomic force microscopy (TMAFM), observed to be ≤100 nm in thickness, and composed of three distinct morphologies. These topographically distinct regions were localized within individual grains and facets of the initial HA surface and included: hemispherical, globular structures (maximum lateral dimension, d=44.7±12.7 nm, peak-tovalley height, h=3.6±2.7 nm); elongated, needle-like structures (minimum lateral dimension, w=31.0±8.5 nm, d=104.4±31.1 nm, h=5.0±3.2 nm), and regions of larger, irregularly shaped
structures that were relatively smooth (d=504.9±219.1 nm, h=104.0±51.7 nm).
Abstract: A/W bioactive glass (BG) particles (600-1000 microns) were soaked in 0.1 M 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) solutions (0.01 g BG per 1 mL solution) at three pH ranges (acidic: 4.45-6.31, neutral: 7.45-7.64 and basic: 10.31-10.42). Crystalline calcium phosphates developed on BG surfaces after soaking in either acidic or neutral solutions. Electron diffraction (ED) results showed that whitlockite and octa-calcium phosphate (OCP) were the newly developed materials on BG in the acidic HEPES solution after soaking for 7 d and 14 d, respectively. Whitlockite also developed on the BG particles in the
neutral solution of 0.5Na-HEPES after soaking for 14 d. No crystalline materials developed on BG surfaces after soaking in the basic Na-HEPES solution up to 14 d. The results of this study demonstrated that the pH of a soaking solution strongly affect both the ions release of the A/W BG particles, and the development of crystalline calcium phosphates on BG particles.
Abstract: Organic polymer coated with hydroxyapatite (so-called apatite) on its surface is a
candidate of new hybrid materials for medical applications since it is expected to show bone-bonding ability and achieve mechanical properties derived from organic substrate. We have shown that some kinds of polyamide films containing carboxyl group or sulfonic group form hydroxyapatite in the simulated body environment, when they are incorporated with calcium chloride. In the present study, the polyamide containing carboxyl groups were modified with silanol groups and its apatite-forming ability was investigated in 1.5SBF, which has ion concentrations 1.5
times those of a simulated body fluid (SBF). It was found that polyamide films modified with silanol groups showed higher ability to induce apatite on its surface in 1.5SBF than the films without the modification, when they were incorporated with calcium chloride.
Abstract: Using an acellular simulated body fluid (SBF), bone-like apatite can be formed on a variety of biomaterials, bioactive or bioinert, after these materials have undergone appropriate treatment(s). This biomimetic apatite-forming process is now applied to tissue engineering scaffolds in an attempt to make the scaffolds osteoconductive. In the current investigation, to form bone-like apatite on polymers such as poly(L-lactic acid) (PLLA) and poly(glycolic acid) (PGA) which degrade fast in aqueous environment, a solution (5SBF) of five times the ion concentrations of SBF was used so that an accelerated apatite formation could be achieved on PLLA and PGA. It was shown that indeed apatite could be formed on PLLA and PGA in 5SBF within 24 hours and that the apatite formed in 5SBF was similar in morphology and composition to that formed in the classical biomimetic process employing SBF or 2SBF. Results obtained in this investigation are very useful for producing osteoconductive scaffolds for bone tissue engineering.
Abstract: The development of phosphate glasses for use in orthopaedic implants has attracted much interest because their chemical and physical properties make them suitable for use as bone-bonding materials. We prepared various compositions of CaO-P2O5-MO or CaO-P2O5-M2O (M: K, Li, Na, Mg, Zn) glasses to measure ion release, solubility and bioactivity. The compositions with (Ca,M)/P molar
ratio 0.6 were fixed P2O5 mol% content at 45.45 mol%, and varying MO or M2O mol% at 10, 20 and 30 mol%. Ca2+ ion release properties were investigated in 0.1M potassium acetate with pH 6 at 37oC by immersing 50 mg of powder into 100 ml of acidic buffer solution. The highest and lowest extent of released Ca2+ ion was observed for composition with 10 mol% of K2O and 30 mol% of MgO, respectively. The weight loss in distilled water at 37oC was measured. Solubility increased with
decreasing CaO content, but decreased with increasing MgO content. Bioactivity in the simulated body fluid at 37oC was measured.
Abstract: The structural change of bovine serum albumin (BSA) was analyzed by means of
ultraviolet (UV) and circular dichroism (CD) spectroscopy due to in contact with ceramics powders such as Al2O3, SiO2, TiO2, ZrO2, hydroxyapatite and b-tricalcium phosphate. The absorbance of the UV spectra increased for the BSA solution in contact with TiO2, ZrO2 and Al2O3, that is, the BSA solution clouded. This indicated the aggregation of BSA after contact with those ceramics powders.
The CD spectroscopy showed that the ordered secondary structure of BSA was diminished on contact with TiO2 and ZrO2. We discussed the protein adsorption property of ceramics on the basis of the magnitude of the interaction forces between proteins and the bioceramics.
Abstract: A series of synthetic apatites bulk samples, characterized by different atomic
substitutions were polarized by field of 1 and 2 kV·cm-1 at 300 °C. The thermally stimulated depolarization currents (TSDC) were measured and the stored electric charge density evaluated. The recent development in the synthesis of non-stoichiometric HA powders, whose chemical composition resembles that of the natural bone, is promising for the realization of improved biomimetic implants for bone substitution; therefore, electrical polarization applied on the ceramic pieces could further enhance the already strong bioactivity of these materials. The depolarization processes in the various material were evaluated by the Arrhenius’ method and
related with the corresponding chemical features; finally, SEM observations of some polarized samples immersed in SBF at 37 °C revealed a wide growth of HA particles within a few days in all the investigated materials.
Abstract: Concentrated H2SO4 acid was applied to pretreatment for the alkaline treatment of
commercially pure titanium, and the effect of acid-etching on apatite-forming ability of
alkaline-treated titanium in a simulated body fluid (SBF) was investigated. Characterization analysis revealed that the concentrated H2SO4 etching formed much amount of sodium titanate, resulting a large amount of formation of apatite in SBF. It is confirmed that the etching in concentrated H2SO4 enhance apatite-forming ability of alkaline-treated titanium.