Days Of Soaking Research Articles

Bioactivity of three CaO-P2O5-SiO2 sol-gel glasses.

Three gel glasses containing 25 mol % of CaO and SiO(2) + P(2)O(5) contents (in mol %): 75 + 0 (S75); 72.5 + 2.5 (S72.5P2.5); and 70 + 5 (S70P5), respectively, were obtained, characterized, and studied when soaked in a simulated body fluid (SBF). The influence of composition in both textural properties (surface area and porosity) and in vitro behavior of glasses was studied. In as prepared S72.5P2.5 and S70P5 glasses, crystalline phosphate nuclei were detected through XRD and FTIR. In addition, N(2) adsorption and Hg porosimetry measurements showed that the surface area increased, whereas the pore volume and the pore diameter decreased as P(2)O(5) in glasses increased. These variations were explained on the basis of the withdrawal of calcium from the glass silica network, due to the calcium-phosphorous bonding. In vitro studies showed that the three compositions were bioactive, because an apatite layer was formed after soaking in SBF. S75 presented the highest initial reactivity but the lowest crystallization rate of the apatite-like phase. For S72.5P2.5, and S70P5 the amorphous calcium phosphate formation was slower than for S75, but the crystallization of apatite was observed after shorter periods in SBF. Furthermore, after 7 days of soaking, the layer thickness decreased as P(2)O(5) in glasses increased.

Mechanical properties and microstructure of bioactive ORMOSILs containing silica particles

We synthesized organically modified silicate (ORMOSILs) gels with colloidal silica (CS) (AEROSIL®) starting from polydimethylsiloxane (PDMS), tetraethoxysilane (TEOS) and calcium nitrate (Ca(NO 3) 2·4H 2O) through sol–gel processing. Dynamic mechanical analysis indicated that relative height of the tan δ peak at about −100 °C increased with an increase in the relative content of the inorganic components. This peak growth was accounted for by the relative increase in PDMS–colloidal silica particle interactions. The colloidal silica could control the mechanical behavior of the hybrids. The gel of a specific composition could deposit apatite within 3 days of soaking in the simulated body fluid (SBF), since it included many calcium ions on the surface.

Correlation between microstructure and properties of biocomposite coatings

A SiO2–CaO–Na2O (SCN) based bioactive glass was used to prepare glass–matrix/Ti particle composite coatings (SCNT). The coatings were obtained by vacuum plasma spray (VPS) on Ti–6Al–4V substrates. Two different deposition methods have been compared: (a) VPS of powders obtained by ball milling of sintered composites; (b) in situ plasma spray of mixed titanium and glass powders. For comparative purposes, pure SCN glass coatings were produced. The coating morphology and microstructure were observed by optical and scanning electron microscopy, compositional analyses by energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). Comparative mechanical tests were carried out by shear tests and by Vickers indentations at the interface between the substrate and the coatings. The bioactivity of glass- and composite coatings was investigated in vitro by soaking them in a simulated body fluid (SBF) with the same ion concentration of the human plasma. All the layers retain their starting composition. The composite coatings obtained by VPS of the powdered presintered composites showed a better mechanical behaviour with respect both to the composite coatings obtained by the in situ method and to the pure glass coatings. Both the glass- and the two kind of composite coatings revealed to be bioactive by the growth of a thick apatite layer after 30 days of soaking in SBF. The electrochemical behaviour of the SCNT coatings was evaluated by means of potentiodynamic anodic polarization curves and free corrosion potential measurements in Ringer solution at 25 °C. For comparative purposes the same analyses were performed on analogous bioactive glass-matrix/Ti particle composite coated samples, based on the system TiO2–SiO2–CaO–B2O3 (TSCB), and obtained both by the in situ and by presintering method as well. The results of the electrochemical tests showed a better corrosion behaviour of the samples coated by VPS of powdered sintered composites with respect to those coated by in situ VPS composites.

Nucleation and growth of hydroxyapatite on an amino organosilane overlayer

An amino organosilane overlayer (NH2-overlayer) was successfully processed on Si/SiO2 substrates. Remarkable nucleation and growth of hydroxyapatite were found to take place on an NH2-overlayer after Si/SiO2 substrates covered with the NH2-overlayer were soaked in supersaturated solutions with respect to Ca2+ and PO43− ions [1.0SBF (simulated body fluid), which contains similar compositions to that in a living body and 1.5SBF in which only Ca2+ and PO43− concentrations are 1.5 times than that in 1.0SBF]. The experimental results demonstrated that HAp nucleation on an NH2-overlayer is related to the electrostatic attractive force between positive NH2-overlayer surface and negative incipient HAp microparticles homogeneously nucleated in 1.5SBF solution at 50°C. On the contrary, fewer HAp particles were observed on negatively charged “OH” terminated self-assembled monolayer (SAM) because of the repulsive interaction. The Ca/P molar ratios of HAp particles increased from 0.92 at the beginning of nucleation in 1.5SBF to 1.63 in 14 days after growth in 1.0SBF at 37°C. After 14 days of soaking in 1.0SBF, a dense HAp film with the thickness up to 8.6 μm was formed on the NH2-overlayer. © 2001 Wiley Periodicals, Inc. J Biomed Mater Res 59: 294–304, 2002

Bonelike apatite growth on hydroxyapatite-gelatin sponges from simulated body fluid.

In vitro bioactivity of gelatin sponges and hydroxyapatite-enriched gelatin sponges was tested through evaluation of the variations in their composition and morphology after soaking in simulated body fluid (1.5) for periods up to 21 days at 37 degrees C. The presence of hydroxyapatite inside the sponges promotes the deposition of bonelike apatite crystals. The deposits are laid down as spherical aggregates, with mean diameters increasing from about 1-2 microm, after 4 days of soaking in simulated body fluid solution, up to about 3.5 microm in the samples soaked for 21 days. Simultaneously, the relative amount of inorganic phase increases up to about 56% wt, leading to a composite material with a composition quite close to that of bone tissue. The inorganic phase is a poor crystalline carbonated apatite similar to trabecular bone apatite.

Nucleation and growth of hydroxyapatite on an amino organosilane overlayer.

An amino organosilane overlayer (NH(2)-overlayer) was successfully processed on Si/SiO(2) substrates. Remarkable nucleation and growth of hydroxyapatite were found to take place on an NH(2)-overlayer after Si/SiO(2) substrates covered with the NH(2)-overlayer were soaked in supersaturated solutions with respect to Ca(2+) and PO(4)(3-) ions [1.0SBF (simulated body fluid), which contains similar compositions to that in a living body and 1.5SBF in which only Ca(2+) and PO(4)(3-) concentrations are 1.5 times than that in 1.0SBF]. The experimental results demonstrated that HAp nucleation on an NH(2)-overlayer is related to the electrostatic attractive force between positive NH(2)-overlayer surface and negative incipient HAp microparticles homogeneously nucleated in 1.5SBF solution at 50 degrees C. On the contrary, fewer HAp particles were observed on negatively charged "OH" terminated self-assembled monolayer (SAM) because of the repulsive interaction. The Ca/P molar ratios of HAp particles increased from 0.92 at the beginning of nucleation in 1.5SBF to 1.63 in 14 days after growth in 1.0SBF at 37 degrees C. After 14 days of soaking in 1.0SBF, a dense HAp film with the thickness up to 8.6 microm was formed on the NH(2)-overlayer.

A novel bioactive and magnetic biphasic material

A novel biphasic material has been synthetised from a sol–gel-derived glass (Si–Ca–P) and a glass–ceramic obtained from a melt-derived glass (Si–Ca–Fe). Both components of such a biphasic mixture are bioactive, but with different kinetics for the growth of an apatite-like layer on the surface of these materials, needing only one day for the sol–gel-derived glass and one month for the glass–ceramic. The glass–ceramic shows magnetic properties. The biphasic material, obtained from a mixture 1:1 of these components, is bioactive, and its surface is coated after 15 days of soaking in SBF. The biphasic material also exhibited magnetic behaviour, useful for hyperthermia.

XPS and SERS Study of Silicon Phthalocyanine Monolayers: Umbrella vs Octopus Design Strategies for Formation of Oriented SAMs

Two strategies are compared for the formation of self-assembled monolayers (SAMs) of silicon phthalocyanines on gold. Silicon phthalocyanines were synthesized with thiol anchoring groups in either eight peripheral side chains (the “octopus”) or with one short thiol in an axial position (the “umbrella”). Both approaches gave phthalocyanines capable of forming SAMs on gold surfaces. The orientation and coverage of the phthalocyanines were compared using ellipsometry, X-ray photoelectron spectroscopy (XPS), and surface-enhanced Raman scattering (SERS). The octopus silicon phthalocyanines form poorly organized SAMs in which the phthalocyanine (Pc) rings are strongly tilted with respect to the gold surface. On average, between 3 and 4 of the thiol “arms” fail to bind to the gold surface, even when limiting coverage is achieved after 7 days of soaking. The film thickness is 22 ± 5 A. In contrast, the umbrella silicon phthalocyanine produces close-packed SAMs within 1 h in which the Pc rings lie parallel to the ...

In vitro characterisation of zirconia coated by bioactive glass

An in vitro evaluation of a biomedical device, which combines the mechanical properties of zirconia substrates with the bioactivity of two different glass layers (AP40 and RKKP), was performed. In this work, data on different kinds of analysis were reported both on as-sintered zirconia samples and on RKKP- and AP40-coated zirconia substrates. Structure, composition and morphology of the apatite layer growth on the coated samples after 30 days of soaking in an acellular simulated body fluid, serum protein adsorption, fibroblasts and human osteoblast-like cells adhesion, growth, morphology and biochemical aspects were studied. Results of soaking test in SBF, revealed the growth of an apatite layer on the surface of the glass-coated samples. Proteins adsorbed to the materials were analysed by sodium dodecyl sulphate–polyacrylamide gel electrophoresis and results evidenced that the two glass-coated materials bound a higher amount of total protein than did the zirconia substrate. Fibroblasts and osteoblast-like cells cultured on RKKP- and AP40-coated zirconia showed a higher proliferation rate, leading to confluent cultures with higher cell density and a generally better expression of osteoblast alkaline phosphatase activity in comparison with zirconia substrate. In conclusion, our results indicate that the surface chemical characteristics of the two glass coatings AP40 and RKKP, with no great differences between them, substantially enhance zirconia integration with bone cells at least in vitro. This effect may be of significance in the stability of glass-coated zirconia orthopaedic and dental implants.

Validation of fluorescent-labeled microspheres for measurement of relative blood flow in severely injured lungs.

The aim of the study was to validate a nonradioactive method for relative blood flow measurements in severely injured lungs that avoids labor-intensive tissue processing. The use of fluorescent-labeled microspheres was compared with the standard radiolabeled-microsphere method. In seven sheep, lung injury was established by using oleic acid. Five pairs of radio- and fluorescent-labeled microspheres were injected before and after established lung injury. Across all animals, 175 pieces were selected randomly. The radioactivity of each piece was determined by using a scintillation counter. The fluorescent dye was extracted from each piece with a solvent without digestion or filtering. The fluorescence was determined with an automated fluorescent spectrophotometer. Perfusion was calculated for each piece from both the radioactivity and fluorescence and volume normalized. Correlations between flow determined by the two methods were in the range from 0.987 +/- 0.007 (SD) to 0.991 +/- 0.002 (SD) after 9 days of soaking. Thus the fluorescent microsphere technique is a valuable tool for investigating regional perfusion in severely injured lungs and can replace radioactivity.

Formation of Calcium Phosphate on Phosphorus-Containing Groups Introduced Substrate

AbstractA calcium phosphate coating over chitin sample was produced by a process based on phosphorylation, Ca(OH)2 treatment and SBF immersion. Ca(OH)2 soaking of the fibers phosphorylated by urea/phosphorus acid (H3PO3) method is found to produce highly crystalline clusters lodged in the fibers which were calcium phosphite mono-hydrate (CaHPO3H2 O). CaHPO3H2O clusters were still present in chitin fibers even after 7 days of soaking, while after 17 days calcium phosphate was observed. While chitin fibers phosphorylated by urea and H3PO4 method and then soaked in saturated Ca(OH) 2 solution at ambient temperature, which lead to the formation of thin coatings formed by partial hydrolysis of PO4 functionalities which were found to stimulate the growth of a calcium phosphate coating on their surfaces after soaking in 1.5×SBF solution for as little as 1 day. EDX analyses of the thin coating gave Ca/P ratio of 1.29, which is speculated to be OCP. The mechanism of formation of the coating is believed to involve dissolution of the CaHPO3 H2O clusters or the OCP upon introduction of the Ca(OH) 2- treated phosphorylated chitin fibers into the 1.5×SBF solution which elevates the Ca2+ ion concentration in the vicinity of the fibers so stimulating calcium phosphate formation from the soaking medium.

The effects of Pain-Free Desensitizer on dentine permeability and tubule occlusion over time, in vitro.

The purpose of this in vitro study was to evaluate the efficacy of a new resin emulsion (Pain-Free Desensitizer) treatment for dentine hypersensitivity, for its ability to decrease dentine permeability. Crown segments were prepared from extracted, unerupted human 3rd molars by horizontal sectioning to remove occlusal enamel and the roots. The specimens were allocated in one of two groups: In group 1, the dentine surface was acid-etched to simulate the patent tubules of hypersensitive dentine. In group 2, the mineralized dentine surface was polished free of smear layer using a hydroxyapatite paste and ultrasonication. The hydraulic conductance of each specimen was then measured to obtain a pretreatment of control value. After a single treatment with resin desensitizer, the permeability was remeasured at 5 min, 1 day, 1 week and 1 month. Between measurements, the specimens were stored in buffer solution to simulate the solubilizing effects of saliva. Parallel specimens were followed by SEM examination. The results showed that a single treatment with resin desensitizer produced large, immediate, reductions in dentine permeability in both acid-etched and mineralized surfaces. In the acid-etched (group 1) specimens, the permeability returned to control values within 7 days, while the permeability of the group 2 specimens remained low even after 30 days of soaking. This simple treatment for occluding dentinal tubules may provide sufficient temporary reduction in dentine permeability to permit the development of natural desensitization.

Rubberwood-polymer composites based on glycidyl methacrylate and diallyl phthalate

Wood-polymer composites (WPC) of rubberwood ( Hevea Brasiliensis ) were prepared by impregnating the wood with glycidyl methacrylate (GMA), combinations of glycidyl methacrylate and diallyl phthalate (GMA-DAP), or diallyl phthalate (DAP) alone. Polymerization was carried out by catalyst-heat treatment. The results showed that WPC based on GMA exhibited greater dimensional stability (results of antishrink efficiency after six days of soaking) about five times than those based on DAP alone. Flexural [Modulus of Elasticity (MOE), Modulus of Rupture (MOR), and toughness], compressive, and impact properties for all the samples tested are improved, especially for those with higher chemical loading.

Bioactive Gel Coatings Derived from Vinyltrimethoxysilane

An ethanol (EtOH) solution of polymerized vinyltrimethoxysilane (VTMS), about 20-mers, was mixed with an aqueous solution of calcium acetate (Ca(OAc)2) and refluxed in N2 for 1 h to give sols of a typical composition VTMS : H2O : EtOH : Ca(OAc)2 = 1 : 9 : 8 : 0.05 (mol). Homogeneous films could be produced, by dip-coating, on Nylon6® and soda-lime glass, but not on polypropylene or polytetrafluoroethylene. The gel films did not deposit apatite within 14 days of soaking in a simulated body fluid whereas films abraded with emery paper as well as bulk gels deposited apatite on the surfaces within 7 days, indicating the present gel was suitable for bioactive coatings on Nylon6®

Asphalt-Treated Permeable Base: Laboratory Testing, Performance, and Predictions

Flexible pavements containing a thin asphalt-treated permeable base (ATPB) layer have been used in California for more than 15 years. The original philosophy upon which use of ATPB is based, the implementation of that philosophy, and observations regarding its effectiveness are examined. Laboratory tests for resilient modulus of ATPB are presented for the as-compacted state, after 3 and 10 days of soaking, and after repetitive loading in the as-compacted and saturated states. The results indicate a loss of stiffness after soaking, and failure caused by stripping and loss of cohesion between the aggregates when subjected to repetitive loading while saturated. The lab test results were used in simulations of fatigue life for pavements with and without ATPB. The results indicate that predicted pavement fatigue lives are improved when ATPB is included in the pavement structure as compared with when aggregate base alone is used, but the improvement diminishes if water damage occurs in the ATPB. Recommendations are made regarding future use of ATPB in flexible pavements.

Transference of Organophosphorus Pesticides to Wine from Fruits during the Process of Making Fruit Wine

Fruit wines were produced using fruits which contained residual organophosphorus pesticides. Some of the dialifos and prothiofos contained in strawberries and some ethion in grapefruit was transferred into the fruit wines (1 to 7%, respectively). The content of pesticides in the wines was maximum after soaking for one day, and then gradually decreased.The rate of this decrease was well described by the following first-order equation.log (Tr)=A-0.4×log(D)where Tr is the content ratio of pesticide transferred from the fruit to the wine (%), A is the content transferred to the wine after one day of soaking, and D is the number of days of soaking.

Effect of the substitution of La2O3 for CaO on the bioactivity of 2.5CaO.2SiO2 glass.

Glasses of the following composition were prepared: (2.5-x)CaO.x/3La2O3.2SiO2 (0 < or = x < or = 1). Their behavior when soaked in a simulated body fluid (SBF) was studied by means of electron microscopy (EM) equipped with an energy-dispersive system (EDS) for elemental analysis, IR spectroscopy, and x-ray diffraction. All the studied glasses react with SBF by forming a calcium phosphate layer. This layer appears to be increasingly thinner with increasing amounts of La2O3 substituted. The experimental results are in good agreement with mechanisms reported in the literature. Moreover they suggest that lanthanum oxide is retained in the layer below the phosphate. After 6 days of soaking, crystalline hydroxyapatite is formed in the case of La2O3 free glass.

Phosphatidylserine-sensitive calcium dependent protein kinase in rice embryo

Protein kinase activity in the embryos of rice ( Oryza sativa L. cv. Nipponbare) during seed soaking in water was assessed under various conditions. This activity was increased by the addition of Ca 2+ and phosphatidylserine (PS), but not by EGTA or Ca 2+ alone. The potent phorbol ester did not augment this increase. The M r of the protein kinases were 55 000 and 56 000. The phosphorylated proteins were separated by two-dimensional gel electrophoresis. Two proteins with M r 40 000 and isoelectric points of 8.9 and 7.6 were significantly phosphorylated with Ca 2+ and PS in vitro. They were first observed after 2 days of soaking, accumulated thereafter and disappeared after 4 days. When the membrane fraction was incubated in Ca 2+ and PS, proteins in the fraction were phosphorylated. Phosphorylation of the proteins with Ca 2+ and PS was inhibited by staurosporine and H-7, but not by W-7 or okadaic acid. The proteins were also found in wheat embryos, but wheat proteins were phosphorylated by Ca 2+ alone. The present data suggest that activation of PS-sensitve Ca 2+ dependent protein kinase associated with membrane and subsequent protein phosphorylation may be involved in regulating the early stages of rice development.

Growth of calcium phosphate on surface-modified cotton

A study of the growth of amorphous calcium phosphate on surface-modified cotton fibres by a combination of scanning electron microscopy/electron diffraction X-ray analysis, micro-FTIR and X-ray photoelectron spectroscopy is reported. Cotton fibres phosphorylated by the urea/phosphorous acid method and then soaked in saturated Ca(OH)2 for approximately one week were found to stimulate the growth of a calcium phosphate coating on their surfaces after soaking in 1.5×SBF for as little as 1 day. Ca(OH)2 soaking of the fibres is found to produce highly crystalline clusters lodged in the fibres which were confirmed by micro-FTIR to be calcium phosphite monohydrate (CaHPO3·H2O). In contrast, phosphorylated fibres not subjected to the Ca(OH)2 treatment did not exhibit calcium phosphate growth upon immersion in 1.5×SBF solution. Soaking of the Ca(OH)2-treated fibres with time in the 1.5×SBF solution produced progressively thicker layers of calcium phosphate on the fibres as confirmed by scanning electron microscopy and X-ray photoelectron spectroscopy. In general, calcium phosphate coatings formed over 1 1–5 day period soaking in 1.5×SBF solution appeared to consist of agglomerations of a large number of small spherical particles, while coatings formed after 17 days of soaking were distinctly chunky, thick and non-uniform in appearance. Micro-FTIR indicated that CaHPO3·H2O clusters were still present in cotton samples even after 4 days of soaking, while after 17 days, only the infrared spectrum typical of calcium phosphate was observed. EDX-measured Ca:P ratios of the coatings, although variable, suggested amorphous calcium phosphate. The mechanism of formation of the coating is believed to involve dissolution of the CaHPO3.H2O clusters upon introduction of the Ca(OH)2-treated phosphorylated cotton into the 1.5×SBF solution which elevates the Ca2+ ion concentration in the vicinity of the fibres so stimulating calcium phosphate formation. It is postulated that phosphite groups chemically bound to the cotton fibre surface or a calcium phosphite coating on the fibres act as nucleation sites for calcium phosphate growth in 1.5×SBF solution.

Studies on the flooding tolerance of soybean seed: varietal differences

To evaluate seed tolerance of soybean seed to flooding, a screening method by soaking seeds at 25°C for 4 days has been established. Of 730 varieties tested, many from South America, India and Southeast Asia appeared highly tolerant to pre-germination flooding. Seed flooding tolerance correlated with seed coat color. Seeds with black colored coat exhibited high tolerance, and some varieties with black seed coat germinated well even after 10 days soaking at 25°C. All yellow seeds failed completely to germinate after 8 days of soaking.