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PubMed2001

Hygroscopicity, phase solubility and dissolution of various substituted sulfobutylether beta-cyclodextrins (SBE) and danazol-SBE inclusion complexes.

The aim of the present work was to characterize hygroscopicity, phase solubility and dissolution properties for various substituted sulfobutylether beta-cyclodextrins (SBEs) and danazol-SBE inclusion complexes. Moisture sorption was measured using a symmetric gravimetric analyzer. The complexes were characterized by powder X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Moisture sorption isotherms for the SBEs and the complexes showed low moisture sorption at RH <60%. The moisture absorption desorption isotherms for the various SBEs showed very little hysteresis, indicating almost complete desorption. Moisture adsorbed by the various SBE was in the order SBE 7>SBE 4>SBE 5 at 95% RH. Powder XRD data for complexes showed the disappearance of characteristic crystalline peaks for danazol or the formation of amorphous entities and DSC showed the disappearance of the peak of fusion of danazol indicating complex formation. Phase solubility of danazol with various substituted SBEs indicated 1:1 stoichiometry of complexes. The apparent stability constant, as determined by the method of Higuchi and Connors, increased as the degree of substitution of SBEs increased and decreased as the temperature increased. The dissolution of the complexes was significantly greater than that of the corresponding physical mixtures indicating that the formation of amorphous complex increased the solubility of poorly soluble danazol. More than 85% of danazol was released in <10 min, compared to 15% danazol release from the physical mixtures.

Calorimetry, Differential Scanning↗
PubMed1995

In vivo setting behaviour of fast-setting calcium phosphate cement.

The in vivo setting behaviour of fast-setting calcium phosphate cement (FSCPC) between femoral muscles of the rat was investigated to evaluate the possible value of FSCPC for medical and dental application. Conventional CPC (c-CPC) and FSCPC were implanted between femoral muscles, and various aspects of the setting behaviour such as setting time, mechanical strength and conversion ratio of cement into hydroxyapatite (HAP: Ca10(PO4)6(OH)2) were measured by the Vicat needle method, diametral tensile strength (DTS) measurement, and quantitative powder X-ray diffraction (XRD) analysis, respectively. The setting time of FSCPC in vivo was 5-7 min, in contrast to 48 min for c-CPC. As a result of its fast setting, set specimens of FSCPC showed higher mechanical strength from the initial stage than c-CPC. Higher DTS values were observed in FSCPC than c-CPC implanted after 24 h. Powder XRD analysis revealed faster conversion of FSCPC than c-CPC into HAP, which was responsible both for the faster setting and higher mechanical strength from the initial stage. We concluded, therefore, that FSCPC may be used for a wide range of clinical applications, i.e. fields where fast setting is required such as orthopaedic, plastic and reconstructive, and oral and maxillofacial surgery.

Animals↗
PubMed1995

Relationships between crystal structures, thermal properties, and solvate stability of dialkylhydroxypyridones and their formic acid solvates.

Four 1,2-dialkyl-3-hydroxy-4-pyridones (DAHPs), which are iron chelators potentially suitable for oral administration, and their formic acid solvates (DAHP-Fs) were examined in powder form by powder X-ray diffraction (PXD), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and hot-stage microscopy (HSM). The experimental PXD pattern of each DAHP-F is different from that of the corresponding DAHP, indicating different crystalline phases. The PXD patterns calculated from the published crystal structures closely resemble the corresponding PXD patterns determined experimentally, indicating that the powdered materials studied are structurally identical with the single crystals previously examined. The DAHPs have similar DSC profiles consisting of melting followed by vaporization. The DSC profiles of the DAHP-Fs share five common features: melting and desolvation of the solvate, crystallization of the nonsolvate, vaporization of the released formic acid, melting of the nonsolvate, and vaporization of the nonsolvate. The weight loss steps in TGA indicate that each DAHP-F contains 1 mol of formic acid/mol of DAHP. The threshold temperature for desolvation of each DAHP increases with decreasing length of the hydrogen bond between the pyridone carbonyl oxygen and the formic acid carboxyl proton, corresponding to an increase in solvate stability. Thus, the relative stabilities of the solvates are delineated and are related to the length of the hydrogen bond between the DAHP and the formic acid molecules.

Calorimetry, Differential Scanning↗
PubMed2000

Ternary early-transition-metal palladium pnictides Zr3Pd4P3, Hf3Pd4P3, HfPdSb, and Nb5Pd4P4.

Several ternary palladium pnictides of the early transition metals have been prepared by arc-melting of the elemental metals and the binary pnictides ZrP, HfP, HfSb2, or NbP, and their structures have been determined by X-ray diffraction methods. The phosphides M3Pd4P3 (M = Zr, Hf) adopt a new structure type (Pearson symbol oP40), crystallizing in the orthorhombic space group Pnma with Z = 4 and unit cell parameters of a = 16.387(2), b = 3.8258(5), and c = 9.979(1) A for Zr3Pd4P3 and a = 16.340(2), b = 3.7867(3), and c = 9.954(1) A for Hf3Pd4P3. The antimonide HfPdSb was identified by powder X-ray diffraction (orthorhombic, Pnma, Z = 4, a = 6.754(1) A, b = 4.204(1) A, and c = 7.701(2) A) and confirmed to be isostructural to ZrPdSb, which adopts the TiNiSi-type structure. The phosphide Nb5Pd4P4 adopts the Nb5Cu4Si4-type structure, crystallizing in the tetragonal space group I4/m with Z = 2, a = 10.306(1) A, and c = 3.6372(5) A. Coordination geometries of pentacapped pentagonal prisms for the early transition metal, tetracapped distorted tetragonal prisms for Pd, and tricapped trigonal prisms for the pnicogen are found in the three structures; tetracapped tetragonal prisms for Nb are also found in Nb5-Pd4P4. In common with many metal-rich compounds whose metal-to-nonmetal ratio is equal or close to 2:1, the variety of structures formed by these ternary palladium pnictides arises from the differing connectivity of pnicogen-filled trigonal prisms. Pnicogen-pnicogen bonds are absent in these structures, but metal-metal bonds (in addition to metal-pnicogen bonds) are important interactions, as verified by extended Hückel band structure calculations on Zr3Pd4P3.

Journal Article↗
PubMed2003

Redetermination of the crystal structure of alpha-copper phthalocyanine grown on KCl.

The crystal structure of a polymorph of copper phthalocyanine (CuPc) grown on a KCl substrate is redetermined by transmission electron diffraction. It has a triclinic unit cell containing one molecule; the crystal does not have a herringbone-type molecular arrangement, which is a common packing mode of planar phthalocyanines. The molecular packing is determined by the diffraction intensity with the aid of the calculation of molecular packing energy. One of the striking features of this polymorph is its stacking mode within a molecular column: the molecular stacking direction projected on a molecular plane is different by an angle of about 45 degrees from that of the alpha-modifications of platinum phthalocyanine (PtPc) and metal-free phthalocyanine (H(2)Pc). A powder X-ray diffraction profile calculated for the polymorph agrees well with that of so-called alpha-CuPc and Rietveld analysis for alpha-CuPc indicates that the CuPc crystals grown on KCl are actually alpha-CuPc; hence, alpha-CuPc is not isostructural with either alpha-PtPc or alpha-H(2)Pc. On the basis of the present results and the reported crystal structures of the planar phthalocyanines that form molecular columns, the polymorphs of the phthalocyanines can be classified into four types distinguished by the molecular stacking mode within the column: alpha(x)-, alpha(+)-, beta(x)- and beta(+)-types.

Journal Article↗
PubMed2004

Influences of layering on theophylline pellet characteristics.

This study evaluated and compared theophylline pellets prepared by both suspension and powder layering processes using the bottom spray coater and the tangential rotary granulator, respectively. Hydroxypropyl methylcellulose (HPMC) and hydroxypropyl cellulose (HPC) were employed as binders at various concentrations. The pellets were coated with Eudragit RS and RL to various levels. It was found that pellet sizes, true densities, and drug contents were comparable and independent of processes and binder levels. However, the increase in binder resulted in lower porosity and pore size, as well as smoother pellet surface. The powder layered pellets possessed higher pellet density and smoother surface than did the suspension layered pellets due to the greater consolidation resulted from tumbling and colliding of pellets. Powder x-ray diffraction pattern revealed that theophylline present in the suspension layered pellets was a mixture of anhydrous form II and hydrate, indicating that transformation could occur in aqueous medium. Drug release from uncoated pellets was found to be complete within 20 min. For coated pellets, the release was markedly decreased with the increase in Eudragit level. Both film thickness and anhydrous/hydrate form influenced the release of drug from the pellets. In general, two methods of layering produced the pellets of slightly differences in pellet properties; however, changes of drug characteristics could occur in suspension.

Cellulose↗
PubMed2006

Characterization of a novel polymorphic form of celecoxib.

A new solid form (Form IV) of celecoxib was prepared in the presence of Polysorbate 80 and HPMC. A celecoxib suspension containing the Form IV had significantly higher bioavailability (>4 times) in dogs than the marketed capsules and the suspension containing bulk drug powders (Form III). The new form was characterized using differential scanning calorimetry, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), infrared spectroscopy, and Raman spectroscopy. The solids separated from the suspension containing the new form showed a melt onset at 145-148 degrees C, which was about 12-15 degrees less than known melting points of Form I, II ,and III of celecoxib. The PXRD pattern of the separated solids was not consistent with any of the known celecoxib crystal forms or the known excipients in the suspension. The formation of the new solid form (Form IV) was dependent upon the concentration and ratio of HPMC and Polysorbate 80. A faster dissolution rate (>2 times) of Form IV was observed compared to the thermodynamically stable form of celecoxib (Form III). There were no measurable changes in the solid state of Form IV either in dried solids or in the suspension for at least 6 months at 40 degrees C and 16 months at 25 degrees C.

Animals↗
PubMed2006

Surface crystallization of indomethacin below Tg.

PURPOSE: To study the surface crystallization of indomethacin (IMC) below T (g) and its effects on the kinetics of overall crystallization. METHODS: Crystal growth rates in liquid layers formed between microscope cover glasses were measured with the top cover glass in place and removed. Polymorphs were identified by powder X-ray diffraction, Raman microscopy, and melting-point determination by hot-stage microscopy. Surface crystals were identified by scratching the sample surface, by cutting the sample to expose its interior, and by analyzing the intensity of X-ray diffraction. Amorphous IMC particles of different sizes were stored at 40 degrees C (T (g)-2 degrees C) and analyzed at different times by differential scanning calorimetry to obtain the kinetics of crystallization. RESULTS: Crystal growth of IMC below T (g) at the free surface was approximately two orders of magnitude faster than that in the bulk, resulting in a surface layer of crystals around a slower-crystallizing interior. Surface crystallization yielded mainly the gamma polymorph. Amorphous IMC powders showed rapid initial crystallization at 40 degrees C, but the crystallization abruptly slowed down at "saturation levels" below 100%; the larger the particles, the lower the "saturation level." CONCLUSION: The faster surface crystallization of IMC than the bulk crystallization leads to unusual crystallization kinetics wherein a rapid initial increase of crystallinity is followed by an abrupt slowdown of crystallization. Surface crystallization should be distinguished from bulk crystallization in modeling and controlling the crystallization of amorphous solids.

Algorithms↗
PubMed2002

Toward the design and synthesis of lithium-ion intercalation into a coordination pi-pi framework host.

A pi-stacked coordination solid, [[[(VO)2(OH)2(C4O4)(phen)2] x H2O]n] (1: phen = phenanthroline), was synthesized by hydrothermal methods and structurally characterized by X-ray single-crystal diffraction. The structure of 1 adopts a neutral open framework in which channeling apertures and windows are surrounded by four oxovanadyl dimers, two squarates, and two pairs of pi-pi interactions of phenanthroline groups; the dimensions of the windows are about 5.38 x 7.55 A along the c axis. Surprisingly, the porous framework with hydrophilic and hydrophobic characteristics was thermally stable up to 250 degrees C, as indicated from powder X-ray diffraction patterns and thermogravimetric analysis. Further investigation of lithium-ion intercalation into the channel matrix of 1 was conformed by 7Li NMR spectroscopy and cyclic votammetry measurements. The present case represents the first example of a porous coordination solid that possesses polar channels capable of mediating lithium-ion insertion.

Journal Article↗
PubMed2004

Synthesis and crystal structure of barium thioborate Ba7(BS3)4S.

The thioborate phase Ba7(BS3)4S was synthesized from solid state reaction and its crystal structure determined by single crystal X-ray diffraction analysis. It crystallizes in the monoclinic space group C2/c (No. 15) with a = 10.1750(15) A, b = 23.970(4) A, c = 10.1692(15) A, beta = 90.095(2) degrees, and Z = 4. The structure consists of isolated trigonal planar (BS3)3- anions, and isolated S2- anions and Ba2+ cations. The additional sulfur anions have five-fold barium coordination, while the barium cations are coordinated by eight or nine sulfur atoms. Powder X-ray diffraction patterns from a bulk sample are compared to the calculated diffraction pattern from the single crystal structural analysis, and there is excellent agreement in general. The vibrational modes of the isolated (BS3)3- units were measured from Raman scattering and IR absorption spectra, and the frequencies agree very well with those found for similar orthothioborate phases.

Journal Article↗
PubMed2004

Freeze-drying of mannitol-trehalose-sodium chloride-based formulations: the impact of annealing on dry layer resistance to mass transfer and cake structure.

The objective of this article was to study the mechanism by which annealing increases the primary drying time in mannitol-trehalose-sodium chloride-based formulations. The thermal events occurring during annealing and the glass transition of the frozen solutions were monitored with differential scanning calorimetry (DSC). Manometric temperature measurement was used to evaluate the dry layer resistances during primary drying. The morphologies of the freeze-dried cakes were examined by scanning electron microscopy (SEM). The degrees of crystallinity of mannitol and sodium chloride (NaCl) in freeze-dried cakes were determined by powder X-ray diffraction (XRD). DSC results indicated that annealing during freezing did not increase the glass transition temperature (Tg') significantly, but there was a distinct decrease of deltaCp at Tg' with annealing, suggesting a decrease in amorphous content. SEM revealed that most mannitol crystallized as the delta-form during annealing at -23 degrees C, and further crystallized as the alpha-form, together with NaCl crystallization, during subsequent annealing at -33 degrees C. The powder XRD results demonstrated that annealing caused crystal growth of mannitol and NaCl, and thus prevented the partial collapse observed without annealing. However, the highly crystallized mannitol blocked the pathways for water vapor escape, contributing to the increase in the dry layer resistance and thus the longer times for primary drying. Freeze-dried cakes without annealing had lower dry layer resistances because partial collapse created larger channels for water vapor escape. Therefore, two-step annealing in freezing makes mannitol-trehalose-sodium chloride-based formulations robust in freeze-drying, but annealing increases the dry layer resistances, thereby extending primary drying.

Chemistry, Pharmaceutical↗
PubMed1996

Development of hydroxyapatite derived from Indian coral.

A simple method of converting the calcium carbonate skeleton of the corals available in the Indian coast into hydroxyapatite granules has been developed. By heating the coral to 900 degrees C, the organic materials were eliminated. Powder X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were employed to characterize the coral and to optimize the processing parameters as well as to confirm the hydroxyapatite formation. The coral used exhibits the presence of both aragonite and calcite phases (dimorphism). At a temperature of 900 degrees C the coral was found to decompose all the carbonate phases. The pre-heated coral is converted into hydroxyapatite by a chemical exchange reaction with di-ammonium phosphate under hydrothermal conditions. The hydroxyapatite obtained was in powder form and does not contain any impurities. The in vitro solubility test of the apatite granules performed in Gomoris, Michalelis, Sorensens, Ringer's and phosphate buffer of pH 7.2 and de-ionized water indicated the stability of the coralline hydroxyapatite.

Animals↗
PubMed2005

Aged titania nanoparticles: the simultaneous control of local and long-range properties.

TiO(2) nanoparticles are obtained by combining a sol-gel preparative route with hydrothermal aging steps, performed in mild conditions, of varying time lengths. Both aged and un-aged samples are thermally treated at 300 and 600 degrees C, for the same length of time. The crystal structures, the phase composition, and crystallite sizes are analyzed by powder X-ray diffraction. Raman spectra of anatase nanocrystals with average sizes of 7-10 nm are reported and the correlation between the Raman band shape of the main feature at 144 cm(-1) and the crystallite size is discussed. Nitrogen physisorption by Brunauer-Emmett-Teller (BET) method is adopted to evaluate the particles surface area and mesopore size and size distribution. The role played by the hydrothermal step in affecting the physicochemical properties of the powders is discussed also with respect to the H(2)O/TiO(2) interactions as apparent from Raman spectroscopy investigations of the O-H stretching range (3000-3800 cm(-1)).

Journal Article↗
PubMed1999

Physicochemical properties of amorphous clarithromycin obtained by grinding and spray drying.

In order to characterize the amorphous clarithromycin (CAM) obtained by grinding and spray drying, physicochemical properties (crystallinity, thermal behavior, stability and solubility parameters) were evaluated. From powder X-ray diffraction, it was estimated that the crystalline state of CAM was changed into an amorphous state by grinding and spray drying. In differential scanning calorimetry measurements, both broad and sharp peaks for crystallization were observed in ground samples, whereas spray dried samples showed one broad peak due to crystallization. As to the stability test under high humidity, structural difference was confirmed between ground CAMs and spray dried CAM. The heat of dissolution of ground CAMs was greater than that of intact CAM. In the solubility parameter measurement, the increase of the special term, deltas, indicated that the energy change was due to the polarity of the surface energy of the powder particles by grinding.

Anti-Bacterial Agents↗
PubMed2006

A microwave route for the synthesis of nanoflakes and dendrites-type beta-ln2S3 and their characterization.

In this article, a simple microwave route was applied for the synthesis of nanoflakes and dendrite-type beta-indium sulfide (In2S3) in high yield (> 97%), using a homogeneous mixture of indium(lll)chloride and thiourea in an ethylene glycol (EG)/polyethylene glycol (PEG400) solvent. The reaction was conducted in a simple domestic microwave oven (DMO). Powder X-ray diffraction (XRD), low resolution and high resolution transmission electron microscopy (LRTEM and HRTEM), selected area electron diffraction (SAED), and energy dispersive X-ray spectroscopy (EDS), were applied to investigate the crystallinity, structure, morphology, and composition of the In2S3 nano-materials. Both the as-synthesized and calcined In2S3 products were a body-centered tetragonal (bct) phase, observed by XRD and HRTEM. The length and width of the resulting nanoflakes were in the range of 70-600 nm and 4-10 nm, respectively. The optical band gap of the powder was determined by diffuse reflectance spectroscopy (DRS) and was found to be 2.44 eV. The electronic properties of the products were studied by measuring the optical absorption spectra using photoacoustic spectroscopy. The band gap calculated by this method was found to be 2.52 eV. A possible mechanism for the formation of nanoflakes/dendrites-type In2S3 was also discussed.

Crystallization↗
PubMed2002

A novel particle engineering technology to enhance dissolution of poorly water soluble drugs: spray-freezing into liquid.

A novel cryogenic spray-freezing into liquid (SFL) process was developed to produce microparticulate powders consisting of an active pharmaceutical ingredient (API) molecularly embedded within a pharmaceutical excipient matrix. In the SFL process, a feed solution containing the API was atomized beneath the surface of a cryogenic liquid such that the liquid-liquid impingement between the feed and cryogenic liquids resulted in intense atomization into microdroplets, which were frozen instantaneously into microparticles. The SFL micronized powder was obtained following lyophilization of the frozen microparticles. The objective of this study was to develop a particle engineering technology to produce micronized powders of the hydrophobic drug, danazol, complexed with hydroxypropyl-beta-cyclodextrin (HPbetaCD) and to compare these SFL micronized powders to inclusion complex powders produced from other techniques, such as co-grinding of dry powder mixtures and lyophilization of bulk solutions. Danazol and HPbetaCD were dissolved in a water/tetrahydrofuran cosolvent mixture prior to SFL processing or slow freezing. Identical quantities of the API and HPbetaCD used in the solutions were co-ground in a mortar and pestle and blended to produce a co-ground physical mixture for comparison. The powder samples were characterized by differential scanning calorimetry (DSC), powder X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), scanning electron microscopy, surface area analysis, and dissolution testing. The results provided by DSC, XRD, and FTIR suggested the formation of inclusion complexes by both slow-freezing and SFL. However, the specific surface area was significantly higher for the latter. Dissolution results suggested that equilibration of the danazol/HPbetaCD solution prior to SFL processing was required to produce the most soluble conformation of the resulting inclusion complex following SFL. SFL micronized powders exhibited better dissolution profiles than the slowly frozen aggregate powder. Results indicated that micronized SFL inclusion complex powders dissolved faster in aqueous dissolution media than inclusion complexes formed by conventional techniques due to higher surface areas and stabilized inclusion complexes obtained by ultra-rapid freezing.

Freezing↗
PubMed1999

Preparation of Nanosize Tin Oxide Particles from Water-in-Oil Microemulsions.

Nanoparticles of tin oxide (SnO2) have been prepared from water-in-oil microemulsions consisting of water, AOT (surfactant), and n-heptane (oil). Precursor hydroxides were precipitated in the aqueous cores of water-in-oil microemulsions and then calcined at 600 degrees C for 2 h to form tin oxide powder. The formation of phase pure tin oxide was confirmed by means of X-ray diffraction analysis. The tin oxide powder was found to be less than 40 nm in particle diameter and to have a higher specific surface area, about 73 m2/g, when compared with tin oxide powder prepared through the conventional precipitation method (19 m2/g). Copyright 1999 Academic Press.

Journal Article↗
PubMed2006

Hemicyanine dye as a surfactant for the synthesis of bicontinuous cubic mesostructured silica.

In this paper, we developed a facile way to synthesize highly ordered optically active MCM-48 at room temperature, by using mixtures of hemicyanine dye N-alkyl-2-[p-(N,N-diethylamino)-o-(alkyloxy)]pyridinium bromide (denoted as o-CnPOCm, Scheme 1) and cetyltrimethylammonium bromide (CTAB) as the structure-directing agents. The mesoporous materials were systematically characterized by powder X-ray diffraction, transmission electron microscopy, nitrogen sorption, and thermogravimetry. The resultant MCM-48 exhibits unusually high thermal stability. For example, in the case of o-C(2)POC(14), it can retain its cubic structure even under calcinations at 900 degrees C for 5 h, although the pore size is shifted to the micropore region because of shrinkage of the framework. The typical surface area and pore volume are 980 m(2)/g and 0.44 cm(3)/g, respectively, for the powder calcined under such a high temperature. This is the first report of room-temperature synthesis of MCM-48 with such good thermal stability using cationic-cationic mixed surfactant as the structure-directing agent. The fluorescence lifetimes of the as-synthesized mesostructured MCM-48 were also measured, and the result showed that the incorporated dye molecules have a 1 order of magnitude longer lifetime than that of free species in solution, showing that the hemicyanine dye molecules are well dispersed within the CTAB surfactant matrix. Furthermore, we compared eight other dye congeners (Scheme 1) to fully investigate the mesophase resulting from the dye-CTAB system. The results show that, upon addition of the dye surfactant to the starting mixtures, the mesostructured silica undergoes an intrinsic phase-transition process; however, specific dye geometry is required to obtain MCM-48 at room temperature. Those functionalities as well as the designed synthesis of this novel mesostructured MCM-48 material promise a bright future in multifunctional optical and electric nano- and microdevices (e.g., waveguides, laser, light-emitting diodes, etc.) and also shed light on the self-assembly behavior in complex colloidal system.

Carbocyanines↗