Effect of Aging on the Dissolution Stability of Glibenclamide/β-Cyclodextrin Complex

The effect of aging on the physicochemical stability of glibenclamide (GB)/β-cyclodextrin (CD) systems and tablets made with CD-complexed GB was studied. Infrared (IR) spectrometry and X-ray diffraction analyses showed that the properties of the products were unaffected even after a storage period of 4 years, except that the crystallinity of GB/CD physical mixture was decreased with aging. The dissolution rate of the kneaded mixture, inclusion complex, and tablets made with the inclusion complex were unaffected on storage for 4 years. Thus, the age-related dissolution problems of GB can be overcome by utilizing the GB/CD complex in the tablet dosage form.     

Solubilization of Glibenclamide with β-Cyclodextrin & its Derivatives

Abstract

Gilbenclamide, a widely used potent hypoglycaemic agent was solubllized using β -Cyclodextrin and β -Cyclodextrin derivatives. Complexes were prepared by kneading method in a molar ratio of 1:1 of the drug and the cyclodextrlns respectively. The Glibenclamide β -Cyelocextrin complex was characterized and evaluated by I.R. studies, Differential Scanning Calorimotry 6 X-ray diffractometry. The in-vitro dissolution rates of drug from inclusion complexes of β Cyclodextrins and its derivatives were compared. A significant Improvement In dissolution lor, rates of Gllbenclamide was observed with Inclusion complexes of all the Cyclodextrins. However, the solubilizing effect was more in case of β-Cyclodextrin derivatives.     

Physical Aspects of Wet Granulation IV – Effect of Kneadign time on Dissolution Rates and Tablet Properties

Abstract

The phsical properties of sucrose-lactoes-strach granulations containing a water soluble drug are characterized, and the relationship between granulaion kneading time and each of the these properties is examined. In addition, the effect of granulation kneading time on the properties of tablets prepared from the granules is examined.     

Inclusion Complexes of Tolnaftate with β-Cyclodextrin and Hydroxypropyl β-Cyclodextrin

Abstract

Tolnaftate, an antifungal agent, was found to form inclusion complexes with both β-cyclodextrin (β-CD) and hydroxypropyl β-cyclodextrins (HPBCDs) with two different degrees of substitution [HPBCD(A)-8% and HPBCD(B)-3%]. Complex formation in the solution state was studied using phase solubility and spectral shift methods. Solid complexes were prepared by the coprecipitation method. Solubilities and dissolution rates were determined for each solid complex, its corresponding physical mixture, and free drug. The increase in solubility of tolnaftate with added HPBCD was found to be significantly greater than with added β-CD. For both HPBCD(A) and HPBCD(B), over the concentration range 0–0.05 M. 1:1 complexes with stability constants of 1460 ± 139 M^-1 and 1860 ± 165 M^-1 were observed, respectively. Over the β-CD concentration range 0–0.02 M, a 1:1 complex with a stability constant of 1190 ± 105 M^-1 was observed. At higher HPBCD concentrations, the increase in solubility was observed to show a positive deviation from linearity (type A_p phase diagram). Using the spectral method, in a 2 5% v/v methanol in water system, the stability constants were determined to be 1020 ± 150 M^-1 1110 ± 120 M^-1 and 1100 ± 260 M^-1 for HPBCD(A), HPBCD(B) and β-CD, respectively. The solid complexes prepared showed improved dissolution over physical mixtures and free drug.     

Effect of particle size on in vitro cytotoxicity of titania and alumina nanoparticles

Aluminium oxide (Al₂O₃) and titanium dioxide (TiO₂) nanoparticles (NPs) have been widely used in nanotechnology-based products. Recently, researchers and the public have raised concerns about the adverse effects of these NPs in biological systems, particularly in humans. The aim of this study was to investigate the possible adverse effects of these two common metal oxide NPs on human lung epithelium cells (A549) and to investigate NP size-dependent effects on these cells, considering both the primary and hydrodynamic particle size. NPs were found to inhibit cell viability and proliferation at the highest concentration level (10?mg/mL) included in this study, as measured by a clonogenic assay. Moreover, cell viability, proliferation and metabolism were impaired to a greater extent by the smaller NPs (5?nm TiO₂ and 10?nm Al₂O₃) relative to the larger particles (200?nm TiO₂ and 50?nm Al₂O₃) included in this study, as measured by cell proliferation and metabolism. Notably, the observed cytotoxic effects correlated to the primary size, rather than the hydrodynamic size. Similarly, NP cytotoxicity was found to be correlated with the NP surface area. These findings highlight the importance of including primary size and surface area information in NP characterisation in cytotoxicity studies.     

Influence of Hydroxypropyl β-Cyclodextrin on Solubility and Dissolution Profile of Ketoprofen in Its Solid Dispersions

Abstract

Solid dispersions of hydroxypropyl β-cyclodextrins (HPB), a highly water soluble derivative of β-cyclodextrin and ketoprofen (KPF), were prepared by kneading, coevaporation, and freeze-drying. X-ray diffraction, differential scanning calorimetry, and scanning electron microscopy were used to investigate characteristics of the solid dispersions and to study the possibility of complexation of the drug with HPB. A marked difference in characteristics of dispersions was observed due to their methods of preparation. The solubility of KPF in the solid dispersions was studied by the dispersed powder technique and was found to have improved considerably over that of the drug pure alone. The dispersions had good compressibiliry. Tablets so compressed displayed good dissolution profiles.     

Effect of Ga on Magnetic and Microstructural Properties of Nd-Fe-Co-B Alloys

1.IntroductionIn this work Ga and Co were added inthe Nd-Fe-B alloys to increase the Curietemperature and improve the temperaturedependence.The improvement of alloy per-formance and the mechanism of coercivitywith the additions of Ga and Co elementsare reported.The Curie temperature of the     

Measurement and Correlation of Electrical Conductivity of β-Cyclodextrin in Water Solution

The electrical conductivity of 4% β-cyclodextrin in water solution had been measured by electrode method from（323.65~353.65） K at atmospheric pressure. The expe...     

Effect of Y2O3 and Total Oxide Addition on Mechanical Properties of Pressureless Sintered β-SiC

The effect of Y2O3 and the total oxide volume fraction (Y2O3 Al2O3) on density and mechanical properties of low temperature (1770～1940℃) pressureless sintered β-SiC ceramics were presented. The optimum temperature for pressureless sintering of β-SiC was found to be～1850℃ and the optimum content of Y2O3 in the oxides was found to be between 40 and 57 wt pct. The highest sintered density was achieved by adding oxides at 14 vol. pct. Both of the highest strength and fracture toughness were achieved at～14 vol. pct oxide addition and yttria concentrations between 40 and 57 wt pct in the oxides. Hardness, on the other hand, was found to be the highest for samples with 14 vol. pct oxide addition and ～64 wt pct Y2O3 in oxides.     

Effect of Different Rare-Earth on Microstructure and Properties of α-Sialon Ceramics

Densified Yb-, Y-, Dy-, Sin- and Nd-α-Sialon ceramics were prepared by two-step hot sintering. The variation of microstructure and properties with different rare-earth was investigated. The ceramics doped with smaller cations （Yb3＋, y3＋ and Dy3＋） are fully composed of α-Sialon, while in the larger cations （Sm3＋ and Nd3＋） doped ceramics also exist a few intergranular phase Mt （Re2Si3-xAlxO3＋xN4-x） in triple-point pockets. With increasing the radius of the rare-earth cations, the elongated α-Sialon grains form instead of the equiaxed grains in Yb-α-Sialon, and the aspect ratio of grains increases. All the ceramics possess high hardness, and the value of 21 GPa is achieved for Yb- and Y-α-Sialon. With increasing the ionic size of rare-earth, the hardness decreases slightly but the toughness tends to increase. Nd-α-Sialon possesses the highest toughness with the value of 5.4 MPa·m^1/2.     

Effect of Humidity on The Formation and Stability of Acetaminophen-β-Cyclodextrin Inclusion Complexes

Abstract

The effect of humidities (75% RH and 100% RH) on the inclusion complex formation and crystallizing behavior of physical mixture and ground mixture of acetaminophen with α-cyclodextrin, β-cyclodextrin or microcrystalline cellulose at 30 °C were studied by DSC thermal analysis, X-ray diffractometer, IR spectrophotometer. The change of water content in the physical mixture and ground mixture when stored at 30 °C, 75% RH or 100% RH was determined. The results indicate that the inclusion complex formation and crystallizing behavior of these mixtures were dependent on the relative humidity and types of cyclodextrins. The physical mixture of acetaminophen and β-cyclodextrin stored at 30 °C and 100% RH was transformed to crystalline inclusion complex, but stored at 75% RH still exhibited a behavior of physical mixture. The ground mixture of acetaminophen and β-cyclodextrin was converted amorphous inclusion complex to crystalline inclusion complex whether stored at 75% RH or 100% RH. However, physical mixture and ground mixture of acetaminophen and α-cyclodextrin or microcrysatlline cellulose when stored at 75% RH or 100% RH belonged to a crystalline physical mixture.     

Effect of Thickness on the Structure and Tribological Properties of MoSx Coating

MoSx coatings were prepared by bipolar-pulse DC unbalanced magnetron-sputtering system with the variation of coating thickness at different Ar pressures.The composition and surface morphology were determined by using energy dispersive X-ray and scanning electron microscopy;the structural characterization was analyzed by X-ray diffraction.The friction and wear properties were investigated by fretting tests in air with less than 10% and 50% relative humidity.At 0.40 Pa pressure,(002) basal plane orientation was formed throughout the coatings.At 0.88 Pa and 1.60 Pa pressures,(002) basal plane orientation was only noticed in the first stage of coating growth(around 0.20 μm in thickness), and then edge orientations with their basal planes perpendicular to the surface would be evolved in the coatings.Humidity has a minor influence on the coatings that have(002) basal plane orientation,whereas the tribological properties of MoSx coatings with edge orientations are greatly affected by humidity.The mechanisms of coating growth and friction and wear processes are discussed.     

Effect of polymerization degree of calcium polyphosphate on its microstructure and in vitro degradation performance

Preparation, characterization and in vitro study of a series of calcium polyphosphate (CPP) with different polymerization degree were reported. A series of CPP with different polymerization degree were prepared by controlling calcining time. Average polymerization degree was analyzed by liquid state ³¹P nuclear magnetic resonance (NMR). The microstructure was observed by scanning electric microscope (SEM). X-ray diffraction (XRD) analysis was used to demonstrate that polymerization degree would not affect the crystal system and space group of CPP. The results showed that polymerization degree increased with the increase of calcining time. Degradation studies were performed during 32 days in physiological saline solution (aqueous solution, 0.9 wt.%NaCl) to assess the effect of polymerization degree on the degradation velocity of the samples. It was also shown that the degradation velocity of CPP (polymerization degree = 13) doubles than another two samples (polymerization degree = 9,19). The results in the present study may be able to provide some fundamental data for controlling CPP degradation.     

Effect of glass–ceramic microstructure on its in vitro bioactivity

Two routes were used to obtain a glass–ceramic composed of 43.5 wt % SiO₂ – 43.5 wt % CaO – 13 wt % ZrO₂. Heat treatment of a glass monolith produced a glass–ceramic (WZ1) containing wollastonite-2M and tetragonal zirconia as crystalline phases. The WZ1 did not display bioactivity in vitro. Ceramizing the glass via powder technology routes formed a bioactive glass–ceramic (WZ2). The two glass–ceramics, WZ1 and WZ2, were composed of the same crystalline phases, but differed in microstructure. The in vitro studies carried out on WZ2 showed the formation of an apatite-like layer on its surface during exposure to a simulated body fluid. This paper examined the influence of both chemical and morphological factors on the in vitro bioactivitity. The interfacial reaction product was examined by scanning and transmission electron microscopy. Both instruments were fitted with energy-dispersive X-ray analyzers. Measurements of the pH made directly at the interface of the two glass–ceramics were important in understanding their different behavior during exposure to the same physiological environment.     

Preparation and Characterization of Albendazole β-Cyclodextrin Complexes

Albendazole (ABZ), mebendazole (MBZ), and ricobendazole (RBZ) are low-soluble anthelmintic benzimidazole carbamate drugs. To increase their aqueous solubility, three different types of β-cyclodextrins (CyDs): β-cyclodextrin (CD), hydroxypropyl-β-cyclodextrin (HPCD), and methyl-β-cyclodextrin (MCD) were used. Solubility depended on the type of CyDs. Increased solubility was obtained when the more substituted CyDs (HPCD or MCD) were used instead of nonsubstituted CD. Stability constants were calculated assuming a 1:1 stoichiometry. Calculated stability constant values depended on initial solubility of drug and pH of the medium. Solid ABZ complexes were prepared by coprecipitation and freeze-drying methods. These products were compared with physical mixtures of ABZ and CyDs. The characterization of these products was made by differential scanning calorimetry (DSC) and drug release studies. True inclusion complexes were obtained only by the freeze-drying method. Drug release studies showed that the freeze-dried inclusion complexes increased the solubility rate of ABZ, although a supersaturation effect was observed when drug release studies were performed in nonsink conditions. A bioavailability study on mice was done with a formulation of ABZ : HPCD complex and was compared to a conventional ABZ suspension. A significantly (p <. 05) shorter T_max of absorption was obtained by using the complex formulation. Greater and significant (p <. 05) differences for AUC and C_max were observed.     

Influence of Hydroxypropyl- β-Cyclodextrin on the Transdermal Permeation and Skin Accumulation of Oxybenzone

ABSTRACT

The objective of the present study was to determine the effects of hydroxypropyl-β-cyclodextrin (HPCD) concentration on the transdermal permeation and skin accumulation of a model ultraviolet (UV) absorber, oxybenzone. The concentration of oxybenzone was held constant at 2.67 mg/mL for all formulations, while the HPCD concentrations varied from 0 to 20% (w/w). Complexation of oxybenzone by HPCD was demonstrated by differential scanning calorimetry. A modified Franz cell apparatus was used in the transdermal experiments, with aliquots of the receptor fluid assayed for oxybenzone by high-performance liquid chromatography. From the permeation data, flux of the drug was calculated. Skins were removed from the diffusion cells at specified time points over a 24-hr period and the oxybenzone content in the skin determined. The aqueous solubility of oxybenzone increased linearly with increasing HPCD concentration, following a Higuchi A_L-type complexation. The stability constant of the reaction was calculated from the phase-solubility diagram and found to be 2047 M^?1. As the concentration of HPCD was increased from 0 to 10%, transdermal permeation and skin accumulation of oxybenzone increased. Maximum flux occurred at 10% HPCD, where sufficient cyclodextrin was added to completely solubilize all oxybenzone. When the concentration of HPCD was increased to 20%, both transdermal permeation and skin accumulation decreased. These data suggest the formation of a drug reservoir on the surface of the skin.     

Effect of Sintering Temperature and Zinc Content on Some Properties of Li-Zn Ferrites

Li-Zn mixed ferrites with composition formula ZnxLi0.5-x/2Fe2.5-x/2O4 (0.2≤x≤0.8) were prepared by the usual ceramic method in 1000~1150℃. The effects of Zn substitution and sintering temperature on the formation, densification, microstructure and a.c. electrical conductivity have been studied. Under the effect of changing the firing temperature and Zn content, high sintered Li-Zn ferrite bodies are achieved. More fine structure bodies having high electrical resistance are obtained at high Zn content     

Effect of Superfine Slag Powder on HPC Properties

A superfine slag powder (SP) made from granulated blast furnace slab incorporating activators by using sepecial miling technique,was used as supplementary cementitious material in high performance concrete (HPC),replacing part of the mass of normal Portland cement,The effects of the SP on the workability,mechanical and crack self-healing properties of HPC were studied,The hydration process and microstructure characteristics were investigated by X-ray diffraction(XRD) and scanning electron microscopy (SEM) techniques,resectively,The crack self-healing capacity was evaluated by Brazilian test,The test results indicate that the SP has especially supplementary effect on water reducing and excellent property of better control of slump loss ,The concrete flowability increases remarkably with of HPC containing SP are higher than the corresponding strength of the control concrete at all ages,The crack self-healing ability is highly dependent on SP content of HPLC.     

Effect of martensitic transformation in Ti–15 at % V β-phase particles on lamellar boundary decohesion in γ-TiAl Part I Derivation of interface decohesion potentials

Molecular statics atomistic simulations of the Ti–15 at% V body-centred cubic (bcc) -phase–-TiAl interface and – lamellar boundary decohesion processes have been carried out to determine the corresponding decohesion potentials. The potentials are subsequently related to the dislocation structure of the interface–boundary. Atomic interactions have been represented using the appropriate embedded atom method (EAM) interatomic potential functions. The results obtained show that the decohesion potential functions are quite complex because they have to account for the instabilities that occur under some modes of interface decohesion and for the periodic character of the interfacial shear. Lastly, the use of decohesion potentials to derive constitutive relations for continuum-type interfacial elements and their implementation in the finite element method are presented. © 1998 Kluwer Academic Publishers     

Effect of fluoride coating on in vitro dynamic degradation of Mg–Zn alloy

A compact and flat fluoride coating with some pores was prepared on a Mg–Zn alloy in order to control its degradation behavior. The electrochemical tests demonstrated that the real impedance (Z_re) of the fluoride-coated Mg–Zn was approximately 10 times as large as that of the untreated alloy. The free corrosion potential (E_corr), compared to that of the uncoated Mg–Zn alloy, increased 646 mV for the coated metal. The free corrosion current (I_corr) of the Mg–Zn specimen with the fluoride film was about one tenth of that of the uncoated one. The in vitro dynamic degradation tests showed that the average weight loss of the fluoride-coated Mg–Zn was lower than that of the untreated alloy in the initial 4 h of the tests, indicating the film could function as a barrier coating on Mg–Zn matrix. However, the coating cracked and peeled severely after 4 h dynamic tests, which implied that the fluoride coating could not endure the sustaining washing of the modified simulated body fluid.