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PubMed2007

Crystallization of indium tin oxide nanoparticles: from cooperative behavior to individuality.

The crystallization pathway of indium tin oxide nanoparticles during solvothermal synthesis in benzyl alcohol was investigated. The synthesis was stopped after different reaction times in the range of 1-24 h, and the structural and morphological characteristics of the products were analyzed by powder X-ray diffraction, electron microscopy, and UV/Vis spectroscopy. Interestingly, the crystallization mechanism does not proceed along a simple nucleation and growth pathway, but involves a two-step process. In the first 12 h an intermediate phase is formed, which consists of nanocrystallites 3-6 nm in size stabilized by an organic matrix. In this organic-inorganic network the nanoparticles are aligned into superstructures, but without any crystallographic orientation. After 12 h the intermediate phase is abruptly transformed into indium tin oxide nanoparticles with the bixbyite structure and with crystallite sizes of about 10-12 nm. This step is accompanied by the disappearance of the organic phase and the loss of the superstructure.

Colloids↗
PubMed2005

Vine-twining polymerization: a new preparation method for well-defined supramolecules composed of amylose and synthetic polymers.

In this article we describe a new method of polymerization called "vine-twining polymerization" for preparation of well-defined supramolecules, which are amylose-polymer inclusion complexes. The method was achieved by enzymatic polymerization of alpha-D-glucose-1-phosphate catalyzed by phosphorylase in the presence of various synthetic polymers such as polyethers, polyesters, poly(ester-ether), and amphiphilic block copolymer. Powder X-ray diffraction (XRD) and 1H-NMR measurements determined the structures of the products to be inclusion complexes. The XRD patterns were completely different from those of amylose and guest polymers. The 1H-NMR spectra of the products indicated that the structures were composed of amylose and guest polymers. The formation process of the inclusion complexes during the enzymatic polymerization was also evaluated. In addition, we revealed that the bulkiness of the end groups and the hydrophobicity of the guest polymers strongly affected the formation of the inclusion complexes. By means of this method of polymerization, a graft polymer having inclusion complexes as side chains was prepared. Furthermore, as an evolution of the "vine-twining polymerization," we attempted a system of parallel polymerization to form an inclusion complex of amylose with a strongly hydrophobic guest polymer.

Amylose↗
PubMed2002

Formation and characterization of high surface area thermally stabilized titania/silica composite materials via hydrolysis of titanium(IV) tetra-isopropoxide in sols of spherical silica particles.

A direct synthetic route leading to titania particles dispersed on nonporous spherical silica particles has been investigated; 5, 10, and 20% (w/w) titania/silica sols mixtures were achieved via hydrolyzation of titanium tetra-isopropxide solution in the mother liquor of a freshly prepared sol of spherical silica particles (Stöber particles). Titania/silica materials were produced by subsequent drying and calcination of the xerogels so obtained for 3 h at 400 and 600 degrees C. The materials were investigated by means of thermal analyses (TGA and DSC), FT-IR, N(2) gas adsorption-desorption, powder X-ray diffraction (XRD), and transmission electron microscopy (TEM). In spite of the low surface area (13.1 m(2)/g) of the pure spherical silica particles calcined at 400 degrees C, high surface area and mesoporous texture titania/silica materials were obtained (e.g., S(BET) ca. 293 m(2)/g for the 10% titania/silica calcined at 400 degrees C). Moreover, the materials were shown to be amorphous toward XRD up to 600 degrees C, while reasonable surface areas were preserved. It has been concluded that dispersion of titania particles onto the surface of the nonporous spherical silica particles increase their roughness, therefore leading to composite materials of less firm packing and mesoporosity.

Journal Article↗
PubMed2002

Covalent grafting of ethylene glycol and glycerol into brucite.

Layered brucite was synthesized at room temperature and, after characterization, was reacted in a closed flask with either ethylene glycol or glycerol. Powder X-ray diffraction patterns have shown that new compounds with interlayer expansions were obtained. New bands attributed to grafting of ethylene glycol and glycerol into the interlayer surface of brucite were detected by FTIR. XPS spectroscopy and thermal analyses (TG/DSC) have shown that nearly all of the hydroxide groups of the layers were replaced by either ethylene glycol or glycerol through Mg-O-C bonds.

Journal Article↗
PubMed1992

Calcium biomineralization in the radular teeth of the chiton, Acanthopleura hirtosa.

A method has been devised for isolating the calcium biomineral from the iron biominerals and organic components present in the major lateral teeth of the chiton Acanthopleura hirtosa. Fourier-transform infrared spectroscopy of the calcium biomineral indicated that it was an apatite material containing carbonate and fluoride ions. Carbonate was not found to be present as a separate phase. The apatite was further separated into low and high density fractions, both of which showed crystallinity intermediate between that of bovine tibia cortical bone and human tooth enamel, as indicated by powder X-ray diffraction analysis. The calcified region of the major lateral teeth was also studied in situ using transmission electron microscopy and electron diffraction analysis, revealing a close spatial relationship between the mineral apatite phase and underlying organic matrix. It is suggested that the architectural arrangement of apatite biomineral and fibrous organic constituents imparts specialized mechanical properties to the tooth making it ideally suited for the task of obtaining food from hard surfaces.

Animals↗
PubMed1995

Preferential uptake of ammonium ions by zinc ferrocyanide.

The concentration of ammonia from dilute aqueous solution could have facilitated many prebiotic reactions. This may be especially true if this concentration involves incorporation into an organized medium. We have shown that (unlike iron(III) ferrocyanide) zinc ferrocyanide,Zn2Fe(CN)6 xH2O, preferentially takes up ammonium ions from 0.01 M NH4Cl to give the known material Zn3(NH4)2[Fe(CN)6]2 xH2O, even in the presence of 0.01 M KCl. KCl alone gave Zn3K2[Fe(CN)6]2 xH2O. Products were characterized by elemental (CHN) analysis and powder X-ray diffraction (XRD). We attribute the remarkable specificity for the ammonium ion to the open framework of the product, which offers enough space for hydrogen-bonded ammonium ions, and infer that other inorganic materials with internal spaces rich in water may show a similar preference.

Ammonia↗
PubMed1985

Iron uptake by teeth and bones: a Mossbauer effect study.

Iron uptake (Fe2+ and Fe3+) by bones, teeth, and dental enamel was studied, in vivo and in vitro, by chemical, powder X-ray diffraction and Mossbauer spectroscopy methods. Atomic absorption tests have revealed the permanent uptake of small amounts of iron by dental enamel soaked in vitro in solutions containing Fe2+. Mossbauer spectra show that the iron attached to the dental enamel stays at the same valency it had in the soaking solutions. Mossbauer measurements of in vivo samples show that iron is present in bones and teeth mainly as Fe3+ (10% Fe2+ in teeth), in compound similar to FeOOH. Iron is released or exchanged from teeth at a much lower rate than from bones.

Animals↗
PubMed1990

Thermal decomposition of developing enamel.

The decomposition of forming, maturing, and mature enamel was studied between room temperature and 1,000 degrees C by powder X-ray diffraction and infrared absorption methods. In mature dental enamel, carbonate decomposition proceeds relatively fast until 500 degrees C and at a slower rate beyond it. In forming and maturing enamel, decomposition is faster and is completed around 800 degrees C. The formation of beta-Ca3(PO4)2 is observed in dental enamel at 500 degrees C. At 1,000 degrees C, the apatite phase in forming and maturing enamel transforms almost completely to beta-Ca3(PO4)2, whereas in mature enamel, even at 1,000 degrees C, only partial decomposition occurs. Infrared results show the appearance in dental enamel of (1) A-type carbonate at room temperature and in the 500-900 degrees C range, in addition to the commonly observed B-type carbonate, and (2) intermediate CO2 molecules during carbonate decomposition (200-500 degrees C).

Animals↗
PubMed2004

Mineralization of decalcified bone occurs under cell culture conditions and requires bovine serum but not cells.

The purpose of this study was to develop an in vitro model system for bone matrix mineralization in the absence of cells. For this model, we utilized EDTA-decalcified new-born rat tibias with the cartilaginous ends intact, allowing us to visually determine the specificity of mineralization within the bone. Our results show that supplementation of DMEM culture medium with 10mM beta-glycerophosphate and 15% fetal bovine serum (FBS) results in non-physiological mineral percipitation in the tibia because of the generation of supraphysiological (5mM) levels of inorganic phosphate in the medium. The same medium supplemented only with inorganic phosphate to a final concentration of 2mM failed to mineralize a decalcified tibia matrix. However, additional supplementation of this medium with as little as 5% FBS resulted in mineralization of those regions of the type I collagen where mineral was found prior to decalcification, with no evidence for mineralization in the cartilage at the bone ends or in the periosteum. Analysis of the mineral by Fourier-transform infrared spectroscopy and powder X-ray diffraction shows that tibias that have been decalcified and then remineralized contain an apatitic mineral that is strikingly similar to the mineral in normal bone. Tendon, a type I collagen matrix not normally mineralized in vivo, also mineralizes when incubated in DMEM containing 2mM Pi and as little as 1.5% FBS, but not when incubated in DMEM without serum. These data indicate that serum contains a nucleator of type I collagen matrix mineralization, and that mineralization of type I collagen under cell culture conditions requires serum but not living cells.

Animals↗
PubMed2003

A study of mineral phase in immobilized rat femur: structure refinements by Rietveld analysis.

The aim of the present work was to examine whether immobilization of a limb influences the structure of bone mineral. The mineral phase in rat femora immobilized for 2 weeks during growth was investigated. Bone mineral was subjected to powder X-ray diffraction, using a scanning method after ashing the bones at 630 degrees C. Occupancy factors of ion positions in bone hydroxyapatite (HAP) were analyzed using the Rietveld refinement method. Occupancy factors of the positions OH(-), Ca(2+), and P(-) were significantly lower in immobilized than in control bones, although the position of ions in the HAP structure did not change. Mineralization of tissue in the immobilized bones was lower than in the controls, but there was no correlation between mineralization and occupancy factors. HAP lattice constants in immobilized bones were slightly but significantly different from those in controls. We conclude that the structure of HAP synthesized in bone during temporary lack of loading differs from that of HAP growing under physiological conditions. The Rietveld refinement method proved to be useful in the estimation of the changes in bone mineral.

Animals↗
PubMed2005

Effect of salt type on hygroscopicity of a new cephalosporin S-3578.

PURPOSE: Effect of salt type on hygroscopicity was evaluated using S-3578 salts. METHODS: The hydration behavior of a sulfate and a nitrate salt of S-3578 were evaluated by powder X-ray diffraction (PXRD), simultaneous measurement of PXRD-differential scanning calorimetry (DSC), moisture sorption analysis, simultaneous measurement of thermogravimetric/differential thermal analyses, and solid state 13C-nuclear magnetic resonance (C-NMR). RESULTS: The sulfate salt incorporated two types of lattice water to form a monohydrate or a trihydrate. Additional water could also be absorbed as channel water to expand the lattice structure. The activation energy for dehydration was very high, probably due to steric hindrance in the lattice structure. The nitrate salt incorporated only one water molecule per compound as the lattice water. The additional water was absorbed as channel water as observed for the sulfate salt. X-ray diffractograms showed little dependence on the salt type under the ambient condition. The hydration number was likely to be affected by the size of the counter acids. CONCLUSIONS: The hygroscopicity of S-3578 salts was significantly altered by the salt type. The difference in the amount of the lattice water could be explained in terms of the difference in the molecular size of the counter acids.

Absorption↗
PubMed2006

Screening of lipid carriers and characterization of drug-polymer-lipid interactions for the rational design of polymer-lipid hybrid nanoparticles (PLN).

PURPOSE: The thermodynamics and solid state properties of components and their interactions in a formulation for polymer-lipid hybrid nanoparticles (PLN) were characterized for screening lead lipid carriers and rational design of PLN. METHODS: Verapamil HCI (VRP) was chosen as a model drug and dextran sulfate sodium (DS) as a counter-ionic polymer. Solubility parameters of VRP, VRP-DS complex, and various lipids were calculated and partition of VRP and VRP-DS in lipids was determined. Thermodynamics of VRP binding to DS was determined by isothermal titration calorimetry (ITC). The solid state properties of individual components and their interactions were characterized using differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). RESULTS: Dodecanoic acid (DA) was identified as the best lipid carrier among all lipids tested based on the solubility parameters and partition coefficients. VRP-DS complexation was a thermodynamically favorable process. Maximum binding capacity of DS and the highest drug loading capacity of DA were obtained at an equal ionic molar ratio of DS to VRP. In the PLN formulation, DA remained its crystal structure but had a slightly lower melting point, while VRP-DS complex was in an amorphous form. CONCLUSIONS: Drug loading efficiency and capacity of a lipid matrix depend on the VRP-DS binding and the interactions of the complex with the lipid. A combined analysis of solubility parameters and partition coefficients is useful for screening lipid candidates for PLN preparation.

Calcium Channel Blockers↗
PubMed2006

Use of surfactants as plasticizers in preparing solid dispersions of poorly soluble API: stability testing of selected solid dispersions.

PURPOSE: The purpose of the study is to evaluate the effect of surfactant-plasticizers on the physical stability of amorphous drug in polymer matrices formed by hot melt extrusion. METHOD: Solid dispersions of a poorly soluble drug were prepared using PVP-K30, Plasdone-S630, and HPMC-E5 as the polymeric carriers and surfactants as plasticizers. The solid dispersions were produced by hot melt extrusion at temperatures 10 degrees C above and below the glass transition temperature (Tg) of the carrier polymers using a 16 mm-Haake Extruder. The surfactants tested in this study included Tween-80 and Docusate Sodium. The particle size of the extrudate was reduced to have mean of 100-200 micron. The physical stability of the solid dispersions produced was monitored at 30 degrees C/60% for six-months and at 60 degrees C/85% for two-months in open HDPE bottles. Modulated differential scanning calorimetry, polarized light microscopy, powder X-ray diffraction and dissolution testing was performed to assess the physical stability of solid dispersions upon stress testing. RESULTS: The dispersions containing HPMC-E5 were observed especially to be susceptible to physical instability under an accelerated stress conditions (60 degrees C/85%RH) of the solid dispersion. About 6% conversion of amorphous drug to crystalline form was observed. Consequently, the system exhibits similar degree of re-crystallization upon addition of the surfactant. However, under 30 degrees C/60%RH condition, the otherwise amorphous Drug-HPMC-E5 system has been destabilized by the addition of the surfactant. This effect is much more reduced in the extruded solid dispersions where polymeric carriers such as Plasdone S-603 and PVP-K30 (in addition to surfactants) are present. Furthermore, the drug release from the solid dispersions was unaffected at the stress conditions reported above. CONCLUSIONS: Possible reasons for the enhanced stability of the dispersions are due to the surfactants ability to lower the viscosity of the melt, increase the API solubility and homogeneity in the carrier polymer. In contrast, while it is possible for the surfactants to destabilize the system by lowering the Tg and increasing the water uptake, the study confirms that this effect is minimal. By and large, the surfactants appear to be promising plasticizers to produce solid dispersions by hot melt extrusion, in so doing improving dissolution rate without compromising the physical stability of the systems.

Calorimetry, Differential Scanning↗
PubMed2006

Molecular interaction among probucol/PVP/SDS multicomponent system investigated by solid-state NMR.

PURPOSE: Effects of polyvinylpyrrolidone (PVP) molecular weight on the solid-state intermolecular interactions among probucol/PVP/sodium dodecyl sulfate (SDS) ternary ground mixtures (GM) and the formation of nanoparticles were investigated by solid-state NMR spectroscopy. MATERIALS AND METHODS: Ternary GMs of probucol were prepared with PVP (K12, K17, K30 or K90) and SDS at a weight ratio of 1:3:1 and were ground for 15, 30 and 60 min. Solid-state interactions were evaluated using powder X-ray diffraction (PXRD) and solid-state cross polarization/magic angle spinning (CP/MAS) (13)C NMR spectroscopy. A high resolution scanning electron microscopy (SEM) was employed to observe nanoparticles of probucol in the GM. RESULTS: The solid-state (13)C CP/MAS NMR results indicate that the low molecular weight PVP interacts with probucol and SDS more strongly than the high molecular weight PVP in the ternary GM. This finding was consistent with the result that smaller drug nanoparticles were obtained using low molecular weight of PVP. SEM images of probucol/PVP K12/SDS confirmed the presence of nanoparticles (15-25 nm) in the GM. CONCLUSIONS: Grinding-induced solid-state interactions among drug, PVP and SDS could be detected using solid state (13)C NMR. The interactions in both probucol-PVP and PVP-SDS should occur simultaneously to generate nanometer-sized particles of probucol.

Magnetic Resonance Spectroscopy↗
PubMed1994

Behavior of a calcium phosphate cement in simulated blood plasma in vitro.

OBJECTIVES: The purpose of this study was to gain a better understanding of the integration of calcium phosphate cement (CPC) implants in biological tissue. METHODS: An in vitro continuous flow system was employed to examine the protracted behavior of disc-shaped specimens of this bioactive material under sustained physiological-like solution conditions. Weight measurement, diameteral tensile strength measurement (DTS), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and powder x-ray diffraction (XRD) were used to characterize the CPC samples as a function of immersion time. RESULTS: When CPC was immersed in simulated blood plasma in which the Ca (2.5 mmol/L) and inorganic phosphate (1.0 mmol/L) levels were kept constant, both the weight and DTS of the specimens steadily increased to about 1.5 times their original values over a period of 20 wk. SEM observations showed new precipitate formations in intimate contact with the original CPC surface. FTIR and XRD analyses revealed that the precipitate was a B-type carbonate hydroxyapatite (OHAp), the type of OHAp observed in bone and dentin. On the other hand, the interior of CPC discs did not show an increase in either bulk density or OHAp content. Thus, the increases in weight and DTS are attributable to the OHAp precipitation on the CPC surface. SIGNIFICANCE: The results suggest that under in vivo conditions, CPC implants would not dissolve in physiological fluids. OHAp coatings may form on the implants, which may enhance bonding of implants to bone by mechanically strengthening the interface between them.

Biocompatible Materials↗
PubMed1995

Non-decay type fast-setting calcium phosphate cement: composite with sodium alginate.

Non-decay type fast-setting calcium phosphate cement (nd-FSCPC) was prepared by introducing sodium alginate (0-2.0 wt%) into the liquid phase of FSCPC. nd-FSCPC was stable even when the cement paste was immersed in distilled water immediately after mixing, whereas conventional FSCPC (c-FSCPC) decayed completely within 1 min upon immersion. The setting time of the cement, approximately 5 min, was not dependent on the presence of sodium alginate. In contrast, the introduction of sodium alginate into conventional CPC, i.e. CPC without neutral phosphate in the liquid phase, resulted in no setting when the amount of sodium alginate introduced was more than 1 wt%. Powder X-ray diffraction analysis revealed no significant difference for the conversion of cement to apatite for any concentrations of sodium alginate studied (0-2.0 wt%). The mechanical strength of the cement increased rapidly with the addition of sodium alginate up to 0.8 wt% when the cement paste was immersed and kept in distilled water at 37 degrees C, whereas further addition of sodium alginate decreased the mechanical strength. The results obtained in this investigation, taken together with sodium alginate's known excellent biocompatibility and absorption behaviour, indicate that the use of sodium alginate composite FSCPC as nd-FSCPC should be of value in orthodontics and oral and maxillofacial surgery where the cement is exposed to blood.

Alginates↗
PubMed1991

Synthesis, characterization, and antitumor activity of 5-iodouracil complexes.

Complexes of 5-iodouracil (5IU) with Mn(II), Co(II), Cu(II), Zn(II), and Cd(II) ions have been prepared, characterized, and subjected to a screening system for evaluation of antitumor activity against Sarcoma-180 (S-180) and L 929 tumor cells. The complexes were characterized by their elemental analysis, infrared spectra, electronic spectra, magnetic measurements, and powder x-ray diffraction. The antitumor activity results indicate that some complexes have good antitumor activity both in vivo and in vitro against S-180 and L 929 tumor cells.

Animals↗
PubMedDate not supplied

Solid-state NMR and IR for the analysis of pharmaceutical solids: polymorphs of fosinopril sodium.

The two polymorphic modifications of fosinopril sodium have been characterized as to their differences in melting behaviour, powder X-ray diffraction patterns, Fourier transform infrared spectra (FTIR), and solid-state 31P- and 13C-NMR spectra. The polymorphs were found to be enantiotropically related based upon melting point, heat of fusion, and solution mediated transformation data. Analysis of the solid-state FTIR and 13C-NMR data indicated that the environment of the acetal side chain of fosinopril sodium differed in two polymorphs, and that there might be cis-trans isomerization about the C6-N peptide bond. These conformational differences are postulated as the origin of the observed polymorphism.

Crystallization↗