Sol-gel bioactive glass-ceramics Part II: Glass-ceramics in the CaO-SiO2-P2O5-MgO system

Ceramics, with basic composition based on the CaO-SiO₂-P₂O₅-MgO system with different Ca+ Mg/P+Si molar ratio (R), were prepared via polystep sol-gel technique. The structure of the obtained ceramic materials has been studied by XRD, FTIR spectroscopy, and SEM. X-ray diffraction showed the presence of akermanite and HA for the sample with R = 1.68 and Mg substituted β-TCP and silicocarnotite for the sample with R = 2.16, after thermal treatment at 1200°C/2 h. The obtained results are in good agreement with FTIR. In vitro test for bioactivity in static condition proved that the carbonate containing hydroxyapatite (CO₃HA) can be formed on the surface of the synthesized samples. CO₃HA consisted of both A- and B-type CO₃²⁻ ions. SEM micrographs depicted different forms of HA particles, precipitated on the surface after soaking in 1.5 simulated body fluid (SBF).      

Comparisons between surfactant-templated mesoporous and conventional sol-gel-derived CaO-B2O3-SiO2 glasses: Compositional, textural and in vitro bioactive properties

Compositional, textural and in vitro bioactive comparisons between surfactant-templated mesoporous (MCBS) and conventional sol-gel-derived CaO-B₂O₃-SiO₂ (CBS) glasses are studied in this paper. CBS glasses are heterogeneous in composition. Due to the heterogeneity, melting boron oxide that formed during the heat treatment will fill in the pores that should have been generated by decomposition of calcium species. So, unlike other conventional sol-gel-derived bioactive glasses that have disordered and widely distributed mesopores, the CBS glasses are almost nonporous. MCBS glasses are more homogeneous in composition than CBS glasses, mainly ascribed to the effect of the surfactant. MCBS glasses of different compositions possess wormhole-like mesoporous structure and have similar pore size. In vitro bioactive tests show that wormhole-like MCBS glasses are more bioactive than CBS glasses, due to their high porosity.     

MAS-NMR studies of lithium aluminum silicate (LAS) glasses and glass-ceramics having different Li2O/Al2O3 ratio

Emergence of phases in lithium aluminum silicate (LAS) glasses of composition (wt%) xLi₂O-71.7SiO₂-(17.7−x)Al₂O₃-4.9K₂O-3.2B₂O₃-2.5P₂O₅ (5.1≤x≤12.6) upon heat treatment were studied. ²⁹Si, ²⁷Al, ³¹P and ¹¹B MAS-NMR were employed for structural characterization of both LAS glasses and glass-ceramics. In glass samples, Al is found in tetrahedral coordination, while P exists mainly in the form of orthophosphate units. B exists as BO₃ and BO₄ units. ²⁷Al NMR spectra show no change with crystallization, ruling out the presence of any Al containing phase. Contrary to X-ray diffraction studies carried out, ¹¹B (high field 18.8 T) and ²⁹Si NMR spectra clearly indicate the unexpected crystallization of a borosilicate phase (Li,K)BSi₂O₆, whose structure is similar to the aluminosilicate virgilite. Also, lithium disilicate (Li₂Si₂O₅), lithium metasilicate (Li₂SiO₃) and quartz (SiO₂) were identified in the ²⁹Si NMR spectra of the glass-ceramics. ³¹P NMR spectra of the glass-ceramics revealed the presence of Li₃PO₄ and a mixed phase (Li,K)₃PO₄ at low alkali concentrations.     

Sol-gel luminescence biosensors: Encapsulation of recombinant E. coli reporters in thick silicate films

A class of sensing elements based on the encapsulation of genetically engineered bioluminescent Escherichia coli (E. coli) reporter strains in sol-gel derived silicates is described. We demonstrate the concept by the immobilization of these bacterial cells in thick silicate films. Heat shock, oxidative stress, fatty acids, peroxides, and genotoxicity reporting bacteria were incorporated in the sol-gel silicates and their luminescence response was compared to that of the non-immobilized culture. All the immobilized bacteria maintained viability and luminescence activity for several months. The bacteria-silicate hybrids can be used either as disposable sensors or in multiple use sensing test-kits, and they can be also integrated in early warning devices operated in continuous flow conditions.     

Organic/inorganic bioactive materials part IV: <Emphasis Type="Italic">In vitro</Emphasis> assessment of bioactivity of gelatin-calcium phosphate silicate/wollastonite hybrids

Biohybrids consisting of gelatin (G) and calcium phosphate silicate/wollastonite (CPS/W) have not been prepared so far. In this work our results are focused on the possibility of obtaining G-CPS/W bioactive hybrids in vitro. XRD, FTIR, SEM/EDS techniques were employed to characterize the synthesized hybrid materials. FTIR shows that before immersion in 1.5 SBF the “red shift” of COO- band for pure G is observed. The presence of this bond could be attributed to the formation of COO-Ca²⁺ via non-biomimetic route. After immersion in 1.5 SBF, FTIR shows the presence of A- and B-type carbonate containing hydroxyapatite (A/B-CO₃HA). ESD and FTIR show that small amount of calcite (CaCO₃) are present after in vitro test in 1.5 SBF for 3 days. XRD reveals that CO₃HA and small amounts of CaCO₃ can be detected after in vitro test. SEM results obtained for immersed samples show that hydroxyapatite (HA) particles fully covered the surface of the hybrids by a layer composed of spherulites. At higher magnification, very small elongated crystallites could be observed.      

HA/CuO/SrCO3梯度复合涂层的制备及体外生物活性

在羟基磷灰石(HA)悬浮液中, 以正丁醇为分散介质, 三乙醇胺为乳化剂, 成骨微量元素化合物CuO 和SrCO₃作为添加剂, Ti片为基材, 壳聚糖(CS)为造孔剂, 依次通过区带电泳分布并在反向电场作用下电 泳沉积, 得到HA/CS/CuO/SrCO₃复合涂层, 经700 ℃高温煅烧2 h后, 制得HA/CuO/SrCO₃复合涂层. 通过X射线衍射(XRD)、 傅里叶变换红外光谱(FTIR)、 场发射扫描电子显微镜(FESEM)、 能量色散光谱仪(EDS)、 劳埃德万能材料试验机、 电化学工作站、 模拟体液培养和抑菌实验等手段对复合涂层进行测试与表征. 结果表明, Ca, Cu和Sr 元素含量在HA/CuO/SrCO₃复合涂层的径向上均呈现梯度分布; 复合涂层与钛基材的结合强度达33.0 MPa; 循环伏安(CV)曲线和Tafel极化曲线测试表明, 复合涂层在N-2-羟乙基哌嗪-N′-2-乙磺酸(HEPES)模拟体液(H-SBF)中电化学性能稳定, 耐腐蚀性较强; 在H-SBF中培养24 d后, 复合涂层表面完全碳磷灰石化; 抑菌实验发现, 复合涂层粉末对大肠杆菌和金黄色葡萄球菌的抑菌率分别为81.82%和71.86%.     

Organic / inorganic bioactive materials Part I: Synthesis, structure and in vitro assessment of collagen/silicocarnotite biocoatings

The silicocarnotite, as an inorganic part of the coatings, has been synthesized using a polystep sol-gel method. The chemical composition of the prepared silicocarnotite sol is described as 58.12 CaO, 29.42 P₂O₅, 12.45 SiO₂ (wt%), where Ca/P+Si = 1,67. The acid soluble type I collagen, as an organic part of the obtained coatings, was mixed with silicocarnotite powder in a weight ratio of 25:75 and 75:25 weight ratio without cross-linkage. The acidity of the obtained mixture was readjust with 25% NH₄OH to pH = 9.0. The mixture was then dried at 37°C for 12 h. The growth of B-type carbonate containing hydroxyapatite (B-type CO₃HA) in which CO₃ ²⁺→PO₄ ³⁻ on the surface of collagen/silicocarnotite coatings soaked in 1.5 simulated body fluid (1.5 SBF) was observed. The nucleation of B-type CO₃HA was estimated on the obtained coatings after 3 days immersion in 1.5 SBF. The negatively charged carboxylate groups from the collagen surface may be responsible for the HA deposition. This was confirmed by the “red shift” of carboxylate groups of collagen molecules in the FTIR spectra. After soaking in 1.5 SBF, the morphology of prepared coatings and HA formation was observed by SEM.     

Sol-gel deposition and luminescent properties of LaMgAl11O19:Ce/Tb phosphor films

Rare earth ions (Ce³⁺, Tb³⁺)-doped LaMgAl₁₁O₁₉ phosphor films were deposited on quartz glass substrates by Pechini sol-gel and dip coating method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), atomic force microscopy (AFM), field emission scanning electronic microscopy (FESEM), photoluminescence (PL) spectra, and lifetimes were used to characterize the resulting films. The results of XRD indicated that the magnetoplumbite structure LaMgAl₁₁O₁₉ phase can be obtained at 1200 °C on quartz glass substrates. This was further verified by the results of FT-IR and TG-DTA. AFM study showed that uniform films have an average grain size of 150 nm and a root mean square (RMS) roughness of 4 nm. The thickness of the films characterized by FESEM is about 340 nm. LaMgAl₁₁O₁₉:Ce³⁺ film showed the parity and spin allowed 5d-4f band emission of Ce³⁺ with a maximum at 350 nm. Ce³⁺, Tb³⁺-codoped LaMgAl₁₁O₁₉ films showed the band emission of Ce³⁺ and characteristic emission of Tb³⁺, namely, ⁵D_3,4-⁷F_J (J=6, 5, 4, 3) due to an efficient energy transfer from Ce³⁺ to Tb³⁺ in the host.     

High performance liquid chromatography/video fluorometry. Part I: Instrumentation

A rapid scanning, two-dimensional fluorometer has been used to obtain Emission-Excitation Matrices (EEMs) of the effluent of an HPLC column. These spectra, obtained “on the fly”, provide qualitative as well as quantitative information about unknown samples. An in-depth discussion of the instrumentation developed and an account of data processing alternatives are presented.     

Pyrolysis study of Sol-gel derived TiO2powders: Part I. TiO2-anatase prepared by reacting titanium(IV) isopropoxide with formic acid

A homogeneous TiO₂ gel sample was prepared, via sol-gel method, hydrolysing titanium(IV) isopropoxide, previously modified by reaction with formic acid. The amorphous TiO₂ gel was characterized using various techniques such as FT-IR, XRD and N₂ adsorption analysis. Thermoanalyses (TG, DTA) coupled with gas chromatographic (GC) and mass spectrometric measurements (MS), by means of a home-assembled instrumental interfaces, were performed in order to quantify the organic component still present in the titania gel and its release during pyrolysis. Several chemical species were evolved and detected in gas phase for temperatures up to 350°C, before crystallization of TiO₂-anatase. This revised version was published online in July 2006 with corrections to the Cover Date.     

Pyrolysis of olive residue/low density polyethylene mixture: Part I Thermogravimetric kinetics

This paper demonstrates the thermal pyrolysis of olive residue, low density polyethylene (LDPE) and olive residue/LDPE mixture in an inert atmosphere of N2 using thermogravimetric analysis (TGA). Measurements were carried out in the temperature range 300K~973K at heating rates of 2K/min, 10K/min, 20K/min and 50K/min. Based on the results obtained, three temperature regimes were selected for studying the nonisothermal kinetics of olive residue/LDPE mixture. The first two were dominated by the olive residue pyrolysis, while the third was linked to the LDPE pyrolysis, which occurred at much higher temperatures. Discrepancies between the experimental and calculated TG/DTG profiles were considered as a measurement of the extent of interactions occurring on copyrolysis. The maximum degradation temperatures of each component in the mixture were higher than those the individual components; thus an increase in thermal stability was expected. The kinetic parameters associated with thermal degradation were determined using Friedman isoconversional method.     

Regularity modes in Raman spectra of polyolefins: Part I. Propylene/olefin copolymers

Behavior of the regularity modes of isotactic polypropylene is analyzed in Raman spectra of a number of random propylene/olefin copolymers. The regularity modes at 809, 841, 973, 998, and 1220 cm⁻¹ decrease in intensity with growth of the content of the incorporated monomer. For the lines at 809, 973, and 1220 cm⁻¹ the rate of intensity damping varies depending on the structure of the incorporated monomer. The type of the incorporated monomer has inconsiderable effect on the evolution of intensity of the regularity bands at 841 and 998 cm⁻¹. Anomalous behavior of the mode at 1220 cm⁻¹ was observed for the propylene/1-butene copolymers.     

On the mechanism of the P2-Na0.70CoO2→O2-LiCoO2 exchange reaction—Part I: proposition of a model to describe the P2-O2 transition

A model was proposed to describe the exchange reaction of sodium by lithium in P2 crystals. The exchange consists on the formation of nucleation centers and then on the growth of O2 domains in P2 crystals from these nucleation centers. Octahedral environments for lithium ions are obtained when one slab over two glides by (2/3,1/3,0) or by (1/3,2/3,0) in P2 structure. The existence of two different gliding vectors should lead to stacking faulted structures that can be simulated using DIFFaX software. The comparison of simulated and experimental XRD patterns for O2-LiCoO₂ (ex-Na_0.7CoO₂) has shown that in that case the growth of the O2 domains in the P2 crystals is faster than the formation of nucleation centers.     

A review of direct liquid introduction interfacing for LC/MS Part I: Instrumental aspects

Summary Considerable progress has been made in the coupling of liquid chromatography and mass spectrometry over the past ten years. Three interfaces tend to dominate the LC/MS market: transport systems, direct liquid introduction, and the thermospray interface. In this paper the developments in direct liquid introduction interfacing for LC/MS will be reviewed. The paper will be published in two parts. Mass spectrometry and applications will be discussed in the second part. This first part of the review concentrates on the various instrumental aspects of direct liquid introduction, such as the design of vacuum systems, the interface probes and the desolvation chambers.     

Synthesis of dipyrrolo[3,4-a:3,4-c]carbazoles: new kinase inhibitors

Two dipyrrolo[3,4-a:3,4-c]carbazole stereoisomers were unexpectedly obtained by Diels–Alder dimerization of 3-indolylmaleimide. Three dimensional structures of both stereoisomers were confirmed by X-ray analysis. Moreover compound 4 inhibits protein kinases in vitro, especially Pim-3, in the sub-micromolar range.     

Investigation of the aromatization of C6+ hydrocarbons on chromia/lanthana-zirconia catalyst: Part I. Catalytic experiments

The aromatization pathway on a chromia/lanthana-zirconia catalyst has been investigated by the conversion of 13 linear and branched hydrocarbons. The product distribution is determined by the educt structure and points to a mechanism without side reactions like isomerization or cracking. The differences in aromatization reactivities could be explained by a mechanism via a stepwise dehydrogenation to a conjugated triene structure. First calculations show that methyl or methylene groups close to terminal double bonds can stabilize these trienes. Such substrates show higher aromatic yields than those without stabilizing groups.     

Tetrad effects in mixed ligand lanthanide chelates. Part I: Lanthanide, EDTA/NTA, IMDA ternary systems

The occurrence of tetrad effects has been studied for the variations in formation constants (logK _MAL ^MA ) of the mixed ligand complexes of the type [Ln(III).A.L.] (where Ln(III)=La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III) or Dy(III); A=EDTA or NTA; L=IMDA), with the number of 4f electrons of the tervalent lanthanides. A differential plot method has been suggested for locating the (minor) breaks at the 4f ³–4f ⁴ and 4f ¹⁰–4f ¹¹ stages in the Ln(III) series.     

Potential antioxidant compounds in Mallotus species fingerprints. Part I: Indication, using linear multivariate calibration techniques

Some Mallotus species are used in traditional medicine in Vietnam and China. Some also show interesting activities, such as antioxidant and cytotoxic ones. Combining fingerprint technology with data-handling techniques allows indicating the peaks potentially responsible for given activities. In this study it is aspired to indicate from chromatographic fingerprints the peaks potentially responsible for the antioxidant activity of several Mallotus species. Relevant information was extracted using linear multivariate calibration techniques, both before and after alignment of the fingerprints with correlation optimized warping (COW). From the studied techniques, Stepwise Multiple Linear Regression is least recommended as it made an inadequate variable selection. Principal Component Regression theoretically can take largely varying variables uncorrelated to the antioxidant activity into account. However, in practice in the actual case study this problem was limited. These problems in principle do not occur using Partial Least Squares (PLS) models. Of the tested PLS methods, Orthogonal Projections to Latent Structures was preferred because of its simplicity, reproducibility, reduced model complexity and improved interpretability of the regression coefficients, yielding a clearer view on the individual contribution of the compounds. Furthermore, reducing analysis times from 60 min to 35 and 22.5 min resulted in the same main compounds, indicated responsible for the antioxidant activity. Models built after alignment by COW did not result in additional information.     

Fracture studies of polypropylene/nanoclay composite. Part I: Effect of loading rates on essential work of fracture

Polypropylene (PP)/Montmorillonite (MMT) nanoclay based composite was prepared by melt compounding with maleic anhydride grafted polypropylene (MA-g-PP) as a compatibilizer in a twin-screw extruder, and the test specimens were injection molded. Mechanical properties such as tensile modulus, flexural modulus, yield strength and maximum percent strains were measured for pure PP and PP based nanocomposite to establish the effect of clay platelet reinforcement. The fracture properties were measured by using the essential work of fracture (EWF) method. PP/clay nanocomposite shows 25% improvement in specific EWF compared to pure PP. The variation of EWF parameters with loading rate is discussed, whilst the mechanisms of fracture are considered in a subsequent paper.     

On the mechanism of the P2-Na0.70CoO2→O2-LiCoO2 exchange reaction—Part II: an in situ X-ray diffraction study

A model was proposed to describe the exchange reaction of sodium by lithium in P2 crystals, it was based first on the formation of nucleation centers and then on the growth of O2 domains in P2 crystals from these nucleation centers. This study has shown that depending on the ratio between the growing and nucleation speeds, O2, O6 or faulted structures are obtained and that this model allows a good analysis of the exchange process. XRD patterns simulation and their comparison with that of experimental O2-LiCoO₂ have shown that there was almost no defects in the O2-LiCoO₂ structure obtained by ion exchange in water. Therefore, this study has shown that the growth of the O2 domains in the P2-Na_0.7CoO₂ crystals is faster than the formation of nucleation centers.This P2-Na_0.7CoO₂→O2-LiCoO₂ exchange reaction was also studied in situ by X-ray diffraction; simulations of key XRD patterns by P2-O2 intergrowths were also achieved. It was shown, in good agreement with the simulations, that the growth of O2 domains was faster than the formation of the nucleation centers and kinetically activated by a P2-Na_0.70CoO₂→P2^*-Na_∼0.50CoO₂ phase transition. For those reasons, the P2-Na_0.70CoO₂→O2-LiCoO₂ exchange reaction in water leads to an O2 phase, with an almost ideal packing.