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PubMed2002

[Approach to the crystalline characteristics of ceftezole sodium].

AIM: To study the crystalline characteristics of ceftezole sodium. METHODS: Ceftezole sodium crystals were obtained from different solvents. X-ray diffraction, DSC, TGA, etc were used to analyze the crytals. RESULTS: Ceftezole sodium crystal was easily obtained in isopropanol-water mixture. It consists of ceftizole sodium monohydrate, which consists of type I and type II two different crystal forms. Powder X-ray diffraction patterns showed differences between type I and the type II crystal forms. Peaks at 8 degrees and 18 degrees in diffractograms of the type I, but at 9 degrees and 18.6 degrees in the type II could be observed. Water molecules in different crystal forms had different combining condition. They lost during 35-117 degrees C in the type I form, but lost during 110-160 degrees C in the type II form. CONCLUSION: Structure of ceftizole sodium monohydrate crystal obtained in different circumstance could be some vary, which influence upon the thermal stability of the compound. The type I crystal form is more stable than the type II.

Cefazolin↗
PubMed1975

Low-temperature ashing of bovine dentine.

The present studies were performed to obtain data on the low-temperature ashing (lta of dentine. Observations of colour and acid solubility, measurement of weight loss, and chemical analyses of carbon, hydrogen, and nitrogen assessed the ashing efficiency. The LTA method was sufficient to deproteinize dentine powder below 300 mesh. The determinations of calcium, magnesium, and phosphorus in dentine showed no significant differences between LTA, muffle furnace ashing (MFA), and wet ashing. The carbonate content was not significantly different after drying and LTA, but apporximately 48% carbonate was lost using MFA. X-ray diffraction patterns of dentine powder showed no detectable changes before and after LTA treatment compared to the patterns after treatment by MFA and/or ethylenediamine extraction.

Animals↗
PubMed2005

Synthesis of mesoporous aluminophosphate (AlPO) and investigation of zirconium incorporation into mesoporous AlPOs.

Mesoporous aluminophosphate materials with variable amounts of zirconium have been synthesized at room temperature using a nonionic surfactant tri-block copolymer (PEO(20)PPO(70)PEO(20)) as the structure-directing agent. Powder X-ray diffraction of as-synthesized and calcined AlPO and ZrAlPO mesoporous materials shows a single broad peak near 2theta = 2.5 degrees, indicative of the average pore-pore correlation distance. Electron probe microanalysis shows that the ratio of P/Al in the powders is approximately 0.5, far lower than 1.0 for an ideal aluminophosphate framework. XRD, TEM, and N2 adsorption data indicate that the calcined samples consist of wormlike tubular materials having surface areas >350 m2/g and pores in the mesopore range. Electron spin resonance (ESR) studies of the gamma-irradiated and evacuated ZrAlPO samples show signals due to Zr3+ that increase with Zr content in addition to signals due to framework defects (i.e., V centers) and H atoms. The line shape and g values observed for Zr3+ are best explained as arising from a trivalent zirconium ion situated at the framework tetrahedral sites.

Journal Article↗
PubMed2006

Effect of pulverization and dehydration on the pharmaceutical properties of calcium lactate pentahydrate tablets.

The effects of heat conduction and pulverization on dehydration kinetics and tablet hardness were studied by a variety of kinetic equations and physical models. The dehydration behavior of unpulverized calcium lactate pentahydrate (UCLP) and pulverized calcium lactate pentahydrate (PCLP) tablets was investigated by using differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). The hardness of both UCLP and PCLP tablets was significantly decreased after dehydration. The relationship between the extent of dehydration and the tablet hardness of both UCLP and PCLP tablets was linear. The results suggest that the reduction in tablet hardness is dependent on the dehydration of crystal water, and the values of the slopes indicate that the bonding energy of the UCLP was stronger than that of the PCLP. The dehydration of both UCLP and PCLP tablets at 55 degrees C followed a one-dimensional diffusion mechanism, whereas dehydration at storage temperatures of 60-80 degrees C followed a three-dimensional diffusion mechanism. UCLP and PCLP tablets contracted in thickness and diameter during dehydration, but final contraction ratios showed that PCLP tablets were more affected than UCLP tablets. In contrast, the micropore radius of both UCLP and PCLP tablets increased after dehydration. Thus, the pharmaceutical properties of calcium lactate pentahydrate (CLP) tablets are affected both by pulverization and by the extent of dehydration of the bulk powder in the tablet formulation.

Calcium Compounds↗
PubMed2004

An automated approach to salt selection for new unique trazodone salts.

PURPOSE: The purpose of this study was to establish an automated approach to salt selection and to search for unique trazodone salts for new applications. METHODS: Automated procedures were developed on a Biomek 2000 automation workstation with stacker and plate reader capabilities. Trazodone was dispensed into 96-well plates, and an automated method was set up to form 104 trazodone salts. Salts were observed under a polarized light microscope to determine crystallinity. After stepwise eliminations, the remaining salts were scaled-up and subjected to differential scanning calorimetry (DSC), powder x-ray diffraction (PXRD), hygroscopic, pH-solubility, density, surface area, and particle size analyses. RESULTS: Oils formed in several cases resulting in preliminary elimination of mesyl and esyl salts and four crystallizing solvents. Crystallinity was observed in 34 of 44 scaled-up trazodone salts. PXRD, DSC, and hygroscopic analyses indicated a number of new salts that were comparable in physicochemical parameters to the marketed HCl salt. Among them, the tosylate salt showed uniqueness for new applications. CONCLUSIONS: Automated procedures can be developed to increase the efficiency of pharmaceutical salt selection. The new tosylate salt gave a unique pH-solubility profile with low solubility over the entire pH range making it a potential candidate for a suspension or prolonged action formulation.

Hydrogen-Ion Concentration↗
PubMed2006

Formulation and characterization of lipid-coated tobramycin particles for dry powder inhalation.

PURPOSE: This study was conducted to develop and evaluate the physicochemical and aerodynamic characteristics of lipid-coated dry powder formulations presenting particularly high lung deposition. METHODS: Lipid-coated particles were prepared by spray-drying suspensions with different concentrations of tobramycin and lipids. The solid-state properties of the formulations, including particle size and morphology, were assessed by scanning electron microscopy and laser diffraction. Aerosol performance was studied by dispersing the powders into a Multistage Liquid Impinger and determining drug deposition by high-performance liquid chromatography. RESULTS: Particle size distributions of the formulations were unimodal, narrow with more than 90% of the particles having a diameter of less than 2.8 microm. All powder formulations exhibited mass median diameters of less than 1.3 and 3.2 microm, as determined by two different laser diffraction methods, the Malvern's Mastersizer and Spraytec, respectively. The fine particle fraction varied within a range of 50.5 and 68.3%. CONCLUSIONS: Lipid coating of tobramycin formulations resulted in a reduced agglomeration tendency and in high fine particle fraction values, thus improving drug deposition. The very low excipients content (about 5% m/m) of these formulations offers the benefit of delivering particularly huge concentrations of antibiotic directly to the site of infection, while minimizing systemic exposure, and may provide a valuable alternative treatment of cystic fibrosis.

Administration, Inhalation↗
PubMed1999

Characterization of racemic species of chiral drugs using thermal analysis, thermodynamic calculation, and structural studies.

The identification of the racemic species, as a racemic compound, a racemic conglomerate, or a racemic solid solution (pseudoracemate), is crucial for rationalizing the potential for resolution of racemates by crystallization. The melting points and enthalpies of fusion of a number of chiral drugs and their salts were measured by differential scanning calorimetry. Based on a thermodynamic cycle involving the solid and liquid phases of the enantiomers and racemic species, the enthalpy, entropy and Gibbs free energy of the racemic species were derived from the thermal data. The Gibbs free energy of formation, is always negative for a racemic compound, if it can exist, and the contribution from the entropy of mixing in the liquid state to the free energy of formation is the driving force for the process. For a racemic conglomerate, the entropy of mixing in the liquid state is close to the ideal value of R ln 2 (1.38 cal.mol-1. K-1). Pseudoracemates behave differently from the other two types of racemic species. When the melting points of the racemic species is about 30 K below that of the homochiral species, is approximately zero, indicating that the racemic compound and racemic conglomerate possess similar relative stabilities. The powder X-ray diffraction patterns and 13C solid-state nuclear magnetic resonance spectra are valuable for revealing structural differences between a racemic compound and a racemic conglomerate. Thermodynamic prediction, thermal analysis, and structural study are in excellent agreement for identifying the nature of the racemic species.

Calorimetry, Differential Scanning↗
PubMed1998

Basic studies on hydroxy apatite cement: I. Setting reaction.

Self-setting cements, alpha D-Cement and alpha DT-Cement, were prepared. They consisted of only the calcium phosphates alpha-TCP, TTCP and DCPA. These cements reacted and hardened in a moist environment at 37 degrees C. The powder X-ray diffraction patterns were taken to examine the conversion of their reactions as a function of time. The cements reacted and produced hydroxyapatite. The optimum powder/liquid ratio of alpha D-Cement was 2.0 and that of alpha DT-Cement was 1.8. The initial setting time of alpha D-Cement was 87.5 m and that of alpha DT-Cement was 107.5 m. The component and the product of these cements are calcium phosphates which are the putative minerals in teeth and bones. Therefore, these cements are useful for oral surgery as bone-filling materials.

Bone Substitutes↗
PubMed2006

Towards an understanding of the structurally based potential for mechanically activated disordering of small molecule organic crystals.

The potential for various small molecule organic crystals to undergo complete mechanically induced disordering is investigated. A model is proposed, which considers changes in free energy required for lattice incorporation of a critical dislocation density. Application requires knowledge of a few physical properties, namely the elastic shear modulus, Burgers vector magnitude, molar volume, melting temperature, and heat of fusion. The model was tested using seven compounds; acetaminophen, aspirin, gamma-indomethacin, salicylamide, sucrose, and two proprietary drug compounds, PFZ1 and PFZ2. Crystalline solids were subjected to high shear, controlled temperature comminution for various durations, after which the samples were examined using powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC). The results verified that acetaminophen, aspirin, and salicylamide, which were suggested by the model to be resistant to complete mechanical disordering, remained fully crystalline, even after 5 h of milling. Sucrose and gamma-indomethacin were both predicted to be susceptible to amorphization, which was confirmed by physical characterization. Single, 3-h grinding experiments were performed on two proprietary compounds, PFZ1 and PFZ2. The model indicated that each should be resistant to complete disordering, a trend held by PFZ1. Evidence of partial disordering of PFZ2 was unexpected and is discussed with respect to possible temperature effects.

Acetaminophen↗
PubMed2006

Development of a nonrigid, durable calcium phosphate cement for use in periodontal bone repair.

BACKGROUND: Calcium phosphate cement (CPC) hardens in situ to form hydroxyapatite and has been used in dental and craniofacial restorative applications. However, when CPC was used in periodontal osseous repair, tooth mobility resulted in the fracture and exfoliation of the brittle CPC implant. The objective of the authors' study was to develop a strong and nonrigid CPC to provide compliance for tooth mobility without fracturing the implant. METHODS: The authors used tetracalcium phosphate, dicalcium phosphate anhydrous and biopolymer chitosan to develop a strong and nonrigid CPC. They used a powder:liquid ratio of 2:1, compared with the 1:1 ratio of a previously developed nonrigid CPC control. Specimens were characterized using a flexural test, scanning electron microscopy and powder X-ray diffraction. RESULTS: After 28 days of immersion, the new cement had a flexural strength (mean +/- standard deviation; n = 6) of 5.2 +/- 1.0 megapascals, higher than 1.8 +/- 1.5 MPa for the control (P < .05) and overlapping the reported strengths of sintered hydroxyapatite implants and cancellous bone. This cement showed a high ductility with a strain at peak load of 6.5 +/- 1.3 percent, compared with 4.4 +/- 1.9 percent for the control; both were 20-fold higher than the 0.2 percent of the conventional CPC. Nanosized hydroxyapatite crystals, similar to those in teeth and bones, were formed in the cements. CONCLUSIONS: The new nonrigid cement, containing nanohydroxyapatite crystals, possessed a high ductility and superior fracture resistance. This strong, tough and nonrigid CPC may be useful in periodontal repair to provide compliance for tooth mobility without fracture. CLINICAL IMPLICATIONS: The results of this study may yield the first self-hardening and nonrigid hydroxyapatite composite with high strength and durability and large deformation capability to be useful in the regeneration of periodontal osseous defects.

Alveolar Bone Loss↗
PubMed2002

Heterobimetallic bismuth-transition metal salicylate complexes as molecular precursors for ferroelectric materials. Synthesis and structure of Bi(2)M(2)(sal)(4)(Hsal)(4)(OR) (4) (M = Nb, Ta; R = CH(2)CH(3), CH(CH(3))(2)), Bi(2)Ti(3)(sal)(8)(Hsal)(2), and Bi(2)Ti(4)(O(i)Pr)(sal)(10)(Hsal) (sal = O(2)CC(6)H(4)-2-O; Hsal = O(2)CC(6)H(4)-2-OH).

The reactions between triphenylbismuth, salicylic acid, and the metal alkoxides M(OCH(2)CH(3))(5) (M = Nb, Ta) or Ti[OCH(CH(3))(2)](4) have been investigated under different reaction conditions and in different stoichiometries. Six novel heterobimetallic bismuth alkoxy-carboxylate complexes have been synthesized in good yield as crystalline solids. These include Bi(2)M(2)(sal)(4)(Hsal)(4)(OR)(4) (M = Nb, Ta; R = CH(2)CH(3), CH(CH(3))(2)), Bi(2)Ti(3)(sal)(8)(Hsal)(2), and Bi(2)Ti(4)(O(i)Pr)(sal)(10)(Hsal) (sal = O(2)CC(6)H(4)-2-O; Hsal = O(2)CC(6)H(4)-2-OH). The complexes have been characterized spectroscopically and by single-crystal X-ray diffraction. Compounds of the group V transition metals contain metal ratios appropriate for precursors of ferroelectric materials. The molecules exhibit excellent solubility in common organic solvents and good stability against unwanted hydrolysis. The nature of the thermal decomposition of the complexes has been explored by thermogravimetric analysis and powder X-ray diffraction. We have shown that the complexes are converted to the corresponding oxide by heating in an oxygen atmosphere at 500 degrees C. The mass loss of the complexes, as indicated by thermogravimetric analysis, and the resulting unit cell parameters of the oxides are consistent with the formation of the desired heterobimetallic oxide. The complexes decomposed to form the bismuth-rich phases Bi(4)Ti(3)O(12) and Bi(5)Nb(3)O(15) as well as the expected oxides BiMO(4) (M = Nb, Ta) and Bi(2)Ti(4)O(11).

Journal Article↗
PubMed1992

Kinetic study of the transformation from tetrahydrate to monohydrate of a new antiallergic, sodium 5-(4-oxo-phenoxy-4H-quinolizine-3-carboxamide)-tetrazolate.

Two hydrates (tetrahydrate, I, and monohydrate, II) of a new antiallergic, sodium 5-(4-oxo-phenoxy-4H-quinolizine-3-carboxamide)-tetrazolate (FR71021), were prepared and characterized by means of infrared spectrometry, thermal analysis, and power X-ray diffraction spectrometry. While I was confirmed to dehydrate readily resulting in an anhydrate form (noncrystalline form) below its critical relative humidity for dehydration, I was also transformed into II under humid conditions. The transformation kinetics from I to II were investigated under varying temperature and humidity conditions by a powder X-ray diffraction technique. The transformation mechanism followed a zero-order reaction, and the apparent transformation rate constant (k) could be described as a function of water vapor pressure (P), temperature (T), and the interaction orders between water vapor pressure and the samples (s): k = A.exp(-Ea/RT).Ps, where Ea is the activation energy and R is the gas constant.

Biotransformation↗
PubMed2006

Structure and thermoelectric characterization of Ba8Al14Si31.

A molten Al flux method was used to grow single crystals of the type I clathrate compound Ba8Al14Si31. Single-crystal neutron diffraction data for Ba8Al14Si31 were collected at room temperature using the SCD instrument at the Intense Pulsed Neutron Source, Argonne National Laboratory. Single-crystal neutron diffraction of Ba8Al14Si31 confirms that the Al partially occupies all of the framework sites (R1 = 0.0435, wR2 = 0.0687). Stoichiometry was determined by electron microprobe analysis, density measurements, and neutron diffraction analysis. Solid-state (27)Al NMR provides additional evidence for site preferences within the framework. This phase is best described as a framework-deficient solid solution Ba8Al14Si31, with the general formula, Ba(8)Al(x)Si(42-3/4x)[](4-1/4x) ([] indicates lattice defects). DSC measurements and powder X-ray diffraction data indicate that this is a congruently melting phase at 1416 K. Temperature-dependent resistivity reveals metallic behavior. The negative Seebeck coefficient indicates transport processes dominated by electrons as carriers.

Journal Article↗
PubMed2006

Humidity-induced changes of the aerodynamic properties of dry powder aerosol formulations containing different carriers.

This paper presents the findings of two related studies. The aim of the first was to study any changes in the aerodynamic properties of salbutamol base powder formulations when different sugars were used as the carriers, after storage at an elevated humidity (75% RH), and whether any such changes (if any) were related to the physical properties of the carriers. The aim of the second was to investigate whether "ageing", i.e. storage of the carrier, drug and blends under desiccation for more than 2 years, affected the aerodynamic properties of salbutamol sulphate powder formulations. Different formulations were prepared, each containing 1.5% (w/w) micronised salbutamol base or sulphate blended with the sieved fraction (63-90 microm) of one of the following sugars: alpha lactose monohydrate, sorbitol, maltose and dextrose. The salbutamol base blends were then stored unprotected at 75% RH (ambient temperature) and salbutamol fine particle fractions (FPFs) were measured by laser diffraction (LD) (% < 5.2 microm) and a multistage liquid impinger (MSLI) (% < 5.3 microm), following aerosolisation at 100 l min(-1) from a model glass inhaler, after storage of each formulation at the elevated conditions for 0, 1 and 6 days. Particle morphology and equilibrium moisture content (EMC) of each formulation prior to and after storage were also evaluated. However, the salbutamol sulphate blends containing either "fresh" or "aged" components were only characterized using LD at 60 l min(-1). Prior to exposure to 75% RH, the lactose blend was found to give the highest FPF of salbutamol (30% by LD and 37% by MSLI), followed by the sorbitol blend (17% by LD and 29% by MSLI), then by the dextrose blend (15% by LD and 25% by MSLI) and finally by the maltose blend (13% by LD and 13% by MSLI). Exposure to 75% RH for 6 days resulted in a small reduction of salbutamol FPF from the lactose blend but drastic diminution of salbutamol FPFs from other blends. After exposure to the high RH, the lactose blend adsorbed ca. 0.4% whilst each of the other sugars took up larger quantities of water (15-40%) and underwent a marked change in the surface texture of the particles. "Ageing" of the carriers and/or formulations did not seem to alter the aerodynamic properties of the drug. "Ageing" of micronised salbutamol sulphate prior to blending, however, was found to improve the FPF of drug. LD was capable of detecting subtle differences between the various formulations and generated FPF results that correlated with those measured by MSLI.

Administration, Inhalation↗
PubMed2006

Neutron diffraction studies of U4O9: comparison with EXAFS results.

Conradson et al. have analyzed X-ray absorption fine-structure spectra of the UO2-U4O9 system and concluded that oxygen atoms are incorporated in U4O9 as oxo groups with U-O distances in the range 1.72-1.76 A. They also found that the uranium sublattice consists of an ordered portion and an additional 'spectroscopically silent' glassy portion. We have carried out studies of powdered U4O9 by neutron diffraction which contradict these conclusions from EXAFS measurements. Our analysis shows that there are no U-O bonds shorter than 2.2 A and that U4O9 is crystallographically ordered with no evidence of a glassy structure.

Journal Article↗
PubMed2001

Enhancement of ibuprofen dissolution via wet granulation with beta-cyclodextrin.

The purpose was to investigate the effect of wet granulation with beta-cyclodextrin (betaCD) on the enhancement of ibuprofen (IBU) dissolution. The effect of the granulation variables on the physical properties as well as the dissolution of tablets prepared from these granules was also examined. Granulation was performed using three granulating solvents: water, ethanol (95 vol%), and isopropanol. Granules were either oven-dried for 2 h or air-dried for 3 days. The granules or respective physical mixtures were compressed into tablets. Powder X-ray diffraction showed that oven-dried granulation resulted in less amorphous entities thatfacilitated IBU-betaCD complexation in solution and enhanced the dissolution of the corresponding tablets compared to the physical mixture with or without oven drying. In contrast, air-dried granulation did not cause any differences in the X-ray diffraction pattern (crystallinity) or the dissolution compared to the physical mixture without drying. Isopropanol and water, as granulating solvents, enhanced the dissolution of the oven-dried batches more than ethanol. The Differential scanning calorimetry (DSC) and Thermogravimetric analysis (TGA) data showed that tablets prepared from oven-dried granules, but not air-dried granules, had lower AH values and percent loss in weight, respectively, than those prepared from the physical mixture as a result of the expulsion of the water molecules from the betaCD cavity and enhancement of the complexation in solution. These results showed that oven-dried granulation of IBU and betaCD provided faster IBU dissolution than the physical mixture; air-dried granulation did not substantially affect the dissolution of IBU.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2001

The spray drying of acetazolamide as method to modify crystal properties and to improve compression behaviour.

Acetazolamide shows a very poor compression ability and tablets must usually be produced through a wet granulation process. However, the possibility to obtain pure acetazolamide for direct compression could be interesting for industrial application. With the scope to obtain a material for direct compression, three different crystallisation methods were chosen, with respect to acetazolamide solvent solubility. (a) Acetazolamide was dissolved in an ammonia solution and then spray dried. It was possible to characterise the spherical particles as a mixture of two polymorphic forms, I and II by Powder X-ray diffraction study. (b) Pure form I was obtained by slowly cooling to room temperature a boiling water solution. (c) Pure form II, the marketed form, was obtained by neutralisation of an ammonia solution. Their compression behaviour was investigated firstly by a rotary press. Whilst pure polymorphic forms I and II could not be compressed, the spray dried particles showed very good compression properties. In fact, tablets were obtained only by spray dried particles, which show very good properties under compression and the absence of capping tendency. On the other hand, it was impossible to obtain tablets from polymorphic forms I and II, whatever compression pressures were used. In order to explain their densification mechanism, a single-punch tablet machine, equipped for the measurement of the upper punch displacement in the die, was used. From calculated Heckel's parameters, it was demonstrated that the spray dried material shows a greater particle rearrangement in the initial stage of compression due to its spherical habit and minor wrinkledness of particle surface. The crystalline structure due to the presence of polymorphic forms I and II concur to lowering the intrinsic elasticity of the material. This fact avoids the risk of the rupturing the interpaticulate bonds, which are formed during the compression, concurring to the consolidation of the tablet.

Acetazolamide↗
PubMed2004

Lipid nanotubes and microtubes: experimental evidence for unsymmetrical monolayer membrane formation from unsymmetrical bolaamphiphiles.

Unsymmetrical bolaamphiphiles, omega- [N-beta-D-glucopyranosylcarbamoyl] alkanoic acids, with even-numbered oligomethylene chains (12, 14, 16, 18, and 20 carbons) self-assembled in water to form lipid nano- and microtubes. The tubular assemblies were separated by centrifugation and examined by transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy to study the molecular packing within the tubular membranes. The nanotubes encapsulated the staining reagent phosphotungstate, which revealed them to be hollow cylinders up to several hundred micrometers long with 30-43-nm outer diameters and 14-29-nm inner diameters. By comparing the membrane stacking periodicity obtained from powder X-ray diffraction analysis of the dehydrated tubes with the molecular packing within single crystals, we found that the nanotubes consist of an unsymmetrical monolayer lipid membrane (MLM) in which the molecules are packed in a parallel fashion. This suggests that the inner surface of the nanotubes is covered with carboxy headgroups and the outer surface with 1-glucosamide headgroups. The inner diameters of the lipid nanotubes could be controlled in the range 17.7-22.2 nm in steps of approximately 1.5 nm/two carbons by varying the oligomethylene spacer length. The microtubes had three types of molecular arrangements. The first type was a symmetrical MLM in which the molecules were packed in an antiparallel fashion. The other two types had unsymmetrical MLM stacking with head-to-head and head-to-tail motifs. Increasing the number of oligomethylene spacers stabilized the unsymmetrical MLM structure in both nano- and microtubes.

Carboxylic Acids↗