A bone replacement-type calcium phosphate cement that becomes more porous in vivo by incorporating a degradable polymer.

This study investigated whether mixing low viscosity alginic acid with calcium phosphate cement (CPC) causes interconnected porosity in the CPC and enhances bone replacement by improving the biological interactions. Furthermore, we hypothesized that low viscosity alginic acid would shorten the setting time of CPC and improve its strength. CPC samples were prepared with 0, 5, 10, and 20% low viscosity alginic acid. After immersion in acetate buffer, possible porosification in CPC was monitored in vitro using scanning electron microscopy (SEM), and the setting times and compressive strengths were measured. In vivo study was conducted by placing CPC in a hole created on the femur of New Zealand white rabbit. Microcomputed tomography and histological examination were performed 6 weeks after implantation. SEM images confirmed that alginic acid enhanced the porosity of CPC compared to the control, and the setting time and compressive strength also improved. When incorporating a maximum amount of alginic acid, the new bone mass was significantly higher than the control group (P = 0.0153). These biological responses are promising for the translation of these biomaterials and their commercialization for clinic applications.

Effects of silica sputtering on adhesion between zirconia and composite resin cores.

Radiofrequency magnetron sputtering of silicon was applied onto zirconia surfaces by use of a non-doped Si wafer at 2%, 5%, 8%, and 10% oxygen volumes. Immediately after sputtering, the contact angle was practically 0 for all oxygen volume specimens. In terms of sustainability of the hydrophilicity, however, 5% oxygen volume was found to be optimal. Scanning electron microscopy and energy dispersive X-ray spectroscopy clearly suggested the presence of silica layer on zirconia surfaces. The shear bond strength of the pre-treated zirconia and resin was 35.03±4.97 MPa, which was approximately 3.5 times higher than that of zirconia without any sputtering treatment (9.26±1.21 MPa). The failure mode of the pre-treated zirconia specimen was cohesive failure, whereas that of the control specimen was observed to be interface failure.

Protein adsorption on spark plasma sintered 2d-, 3d- and lamellar type mesoporous silicate compacts.

The preparation of lamellar type mesoporous silica (MPS) compact through the spark plasma sintering (SPS) and the adsorption/desorption of protein onto MPS compact are reported to be compared with those onto 2d-hexagonal and 3d-cubic type MPS compacts. A lamellar-type MPS powder (MPS-la) was prepared using triblock copolymer, PEO5PPO68PEO5, and was compacted in a carbon die and heated at 500°C for 5 min under uniaxial pressure. The products are referred to as MPS-la-500. The MPS compacts keep the lamellar type mesoporous configuration. The adsorbed amount of protein onto MPS-la-500 was 100 mg/g, while that on MPS-la was 130 mg/g, and the former decreased by 23%. However, its decreasing ratio of the protein adsorption on MPS-la-500 was less than those of 2d-hexagonal and 3d-cubic type MPS compacts, which were 73 and 34%, respectively. The released amount of protein into PBS solution from MPS-la-500, which was soaked in the protein solution for 48 h, increased with the soaking time, while those from 2d- and 3d-type MPS compacts reached to plateau for 4 h of soaking. The lamellar type MPS compact was found to be easier to absorb and release proteins, which may be due to the large aperture of the mesoporous configuration.

Kinetic modelling of cytochrome c adsorption on SBA-15.

The adsorption capacity of mesoporous silicate (MPS) materials as an adsorbent for protein adsorption from the aqueous phase and the mechanism of the adsorption processes by comparative analyses of the applicability of five kinetic transfer models, pseudo-first-order model, pseudo-second-order model, Elovich kinetic model, Bangham's equation model, and intraparticle diffusion model, were investigated. A mixture of tetraethyl orthosilicate (TEOS) and triblock copolymer as a template was stirred, hydrothermally treated to form the mesoporous SBA-15 structure, and heat-treated at 550°C to form the MPS material, SBA-15. The synthesized SBA-15 was immersed in a phosphate buffered saline (PBS) solution containing cytochrome c for 2, 48, and 120 hours at 4°C. The TEM observations of proteins on/in mesoporous SBA-15 revealed the protein behaviors. The holes of the MPS materials were observed to overlap those of the stained proteins for the first 2 hours of immersion. The stained proteins were observed between primary particles and partly inside the mesoporous channels in the MPS material when it had been immersed for 48 hours. For MPS when it had been immersed for 120 hours, stained proteins were observed in almost all meso-scale channels of MPS. The time profiles for adsorption of proteins can be described well by Bangham's equation model and the intraparticle diffusion model. The Bangham's equation model is based on the assumption that pore diffusion was the only rate controlling step during adsorption, whose contribution to the overall mechanism of cytochrome c adsorption on SBA-15 should not be neglected. The kinetic curves obtained from the experiment for cytochrome c adsorption on SBA-15 could show the three steps: the initial rapid increase of the adsorbed amount of cytochrome c, the second gradual increase, and the final equilibrium stage. These three adsorption steps can be interpreted well by the multi-linearity of the intraparticle diffusion model, proving the significant role of intraparticle diffusion as one of the rate controlling mechanisms.

Phosphorylated, cellulose-based substrates as potential adsorbents for bone morphogenetic proteins in biomedical applications: a protein adsorption screening study using cytochrome C as a bone morphogenetic protein mimic.

Screening studies aimed at identifying useful biomedical materials that (when combined with implants) can attract bone morphogenetic proteins to their surfaces have been conducted. In this paper, the screening process has involved carrying out protein adsorption studies using cytochrome C, as a BMP protein mimic on phosphorylated cellulose-based substrates. These studies have shown that phosphorylation of cellulose produces materials that are capable of attracting the adsorption of cytochrome C to their surface. In contrast, negligible cytochrome C adsorption was observed on the unphosphorylated cellulose-based materials. The selective uptake of the positively charged cytochrome C (from solutions at pH 9.51) by the negatively charged phosphorylated cotton and microcrystalline cellulose substrates was primarily due to this protein's high isoelectric point (i.e.p) of 9.8 which gives it a positive charge at pH

Effect of drying conditions during synthesis on the properties of hydroxyapatite powders.

The effect of the drying conditions during the hydroxyapatite (HAp) powder synthesis on the size and microstructure was studied. The starting materials were agitated in water, dried at 60-150 degrees C, and heat-treated at 720 degrees C. The heat-treated HAp powders were crystalline, and their particle sizes decreased with an increase in the drying time, but were independent of the drying temperature. For a 3 day drying period, it was 1.61 microm, and 0.55 microm for 21 days. The surface zeta potential of the HAp powder with a long drying period was more negatively charged than that from the short drying period. The average primary particle sizes of the HAp powders seem to be almost equivalent, and so the drying period may be related to the dispersibility of the primary particles, and may lead to a small HAp particle size.

Specific response of osteoblast-like cells on hydroxyapatite layer containing serum protein.

Accelerations of bone-like apatite deposition and cell growth on an electrically polarized ceramic hydroxyapatite have been reported. A relationship between these phenomena was investigated in a previous report, and then it was suggested that osteoblast-like cell's (MC3T3-E1) growth had relevance to the mineral growth. The effect of the formed apatite layer especially appeared to be on the cell adhesion. The acceleration of cell proliferation on the polarized HAp has been shown using fibroblastic cell (L929) and nerve cell (SK-N-SH) lines, therefore the effect of the layer on L929 and SK-N-SH was investigated to support the mechanism of acceleration of cell proliferation by polarization of HAp. In this study, the effect of the bone-like apatite layer was not confirmed on L929 cell's growth. On the other hand, the acceleration of nerve cell's proliferation was confirmed on the formed apatite layer. However, the remarkable improvement of the cell adhesion of SK-N-SH was not confirmed on the apatite layer. Consequently, it was considered that the bone-like apatite containing serum protein obtained by the coprecipitation of bone-like apatite and serum protein has a pronounced role only in the activity of osteoblast-like cells.

Growth of calcium hydroxyapatite (Ca-HAp) on cholesterol and cholestanol crystals from a simulated body fluid: A possible insight into the pathological calcifications associated with atherosclerosis.

An experimental study into calcium phosphate (CP) nucleation and growth on cholesterol and cholestanol surfaces from a supersaturated simulated body fluid (SBF) is presented with the overall aim of gaining some fundamental insights into the pathological calcifications associated with atherosclerosis. Soaking of pressed cholesterol disks at physiological temperature in SBF solutions was found to lead to CP nucleation and growth if the disks were surface roughened and if an SBF with concentrations of the calcium and hydrogen phosphate ions at 2.25x physiological concentrations was used. The CP phase deposited was shown via SEM micrographs to possess a florette type morphology akin to that observed in earlier reported studies. The use of recrystallised cholesterol and cholestanol microcrystals as substrates for soaking in SBF facilitated the observation of CP deposition. In general, cholesterol recrystallised from polar solvents like 95% ethanol as a cholesterol monohydrate phase which was a better substrate for CP growth than cholesterol recrystallised from more non-polar solvents (e.g., benzene) which produced anhydrous cholesterol phases. CP was also observed to form on recrystallised cholestanol microcrystals, a molecule closely related to cholesterol. Inductively coupled plasma optical emission spectrometry (ICP-OES) data gave confirmation that Ca:P mole ratios of the grown CP were 1.3-1.5 suggesting a mixed phase of octacalcium phosphate (OCP) and Ca-deficient HAp and that the CP coating grows (with time of soaking) on the substrates after nucleation in the SBF growth medium. Infrared (IR) spectra of the extracted coatings from the cholesterol substrates confirmed that the CP phase deposited is a semi crystalline HAp with either carbonate substituted into its structure or else co-deposited as calcium carbonate. Soaking experiments involving modified cholesterol substrates in which the OH group in the molecule was replaced with the oleiyl or phosphonate group showed no CP nucleation and growth. This observation illustrates the importance of the known epitaxial relationship between cholesterol and HAp (which theoretically predicts favourable deposition of one phase upon the other) and the consequences of its destruction (by chemical modification of the cholesterol). In the case of the phosphorylated cholesterol, failure of this substrate to nucleate CP phases may have also been caused by the reduction in concentration of free solution Ca2+ in the SBF medium by complexation with the phosphonate groups on the phosphorylated cholesterol. This would have reduced the ion product of Ca2+ and inorganic phosphate and lowered the degree of supersaturation in the SBF medium.

Reaction properties of catalytic antibodies encapsulated in organo substituted SiO2 sol-gel materials.

Catalytic antibodies (38C2 and 84G3) were encapsulated in hybrid organic-inorganic sol-gel powder prepared from tetraethoxysilane (TEOS) and organoalkoxysilanes, then used to catalyze enantioselective aldol reactions. Sol-gel immobilization enhanced antibody stability with respect to the effect of temperature and organic solvent concentration.

Detoxification of bisphenol A and nonylphenol by purified extracellular laccase from a fungus isolated from soil.

Purified laccase from a fungus (family Chaetomiaceae) was used for the enzymatic oxidation of bisphenol A and nonylphenol, endocrine-disrupting chemicals. It rapidly oxidized both chemicals in the absence of mediators and within 24 h their estrogenic activities were completely removed.

Catalytic properties of lipases immobilized on various mesoporous silicates.

Lipases SP525, AK, LIP, and PS were immobilized on three kinds of mesoporous silicates (FMS, PESO, and SBA) with diameters of 27 to 92 A. The amount of lipase activity adsorbed on these supports was related to the pore size of the silicate. Enantioselectivities of immobilized lipases were similar to those of free lipases, and recycling could be done in both aqueous and organic solvents.

Formation of highly oriented hydroxyapatite in hydroxyapatite/titanium composite coating by radio-frequency thermal plasma spraying.

Highly oriented hydroxyapatite (HA) coatings with excellent adhesion were successfully obtained on titanium (Ti) and titanium alloy through a radio-frequency thermal plasma spraying method. The ratio of HA and Ti powders supplied into the plasma was precisely controlled by two microfeeders so as to change the composition from Ti-rich to HA-rich toward the upper layer of the formed coatings. The bond (tensile) strength of the HA/Ti composite coatings was ca. 40-50 MPa. XRD patterns showed that the topmost HA layer of the coatings had an apatite structure with (00l) preferred orientation. The degree of this orientation showed a tendency to increase with an increase in the substrate temperature during spraying.

Preparation and catalytic performance of lipases encapsulated in sol-gel materials.

Three kinds of lipases (from Candida antarctica, Pseudomonas cepacia, and Pseudomonas fluorescens) were encapsulated in inorganic matrices by the sol-gel method in order to synthesize chiral compounds by kinetic resolution. Sol-gel lipases prepared with vinyltriethoxysilane had higher hydrolysis activity for 2-octyl acetate than those with other silane precursors: tetramethoxysilane, methyltrimethoxysilane, and propyltrimethoxysilane.