Morphology control of amino acid particles in interfacial crystallization using inkjet nozzle

The aim of this study is to apply the inkjet technique to liquid–liquid interfacial crystallization. Instillation with an inkjet nozzle was compared with the batch process in order to evaluate the effectiveness of the inkjet technique for controlling particle morphology. The effects of amino acid solution concentration and organic solvent type on particle properties were investigated for instillation with an inkjet nozzle. The morphology of alanine and glycine particles was observed by scanning electron microscopy and X-ray powder diffraction. The inner structure of alanine and glycine particles was investigated by cutting particles with an ion milling machine. Controlling particle size by adjusting the droplet size in the instillation with an inkjet nozzle was found to be feasible. Most alanine and glycine particles produced by instillation were spherical, whereas most particles produced by the batch process were non-spherical. A higher concentration of amino acid in the solution may lead to the generation of solute particles at the spherical interface. It was found that the surface structure of alanine particles changed when using two kinds of organic solvents as anti-solvents. In addition, instillation allowed for β-glycine to be identified and the crystal polymorph of the particles to be controlled.     

Supersaturation produces high bioavailability of amorphous danazol particles formed by evaporative precipitation into aqueous solution and spray freezing into liquid technologies

The bioavailability of high surface area danazol formulations was evaluated in a mouse model to determine what effect high supersaturation, as measured in vitro, has on the absorption of a poorly water soluble drug. Danazol, a biopharmaceutics classification system II (BCS II) compound, was used as the model drug. Evaporative precipitation into aqueous solution (EPAS) and spray freezing into liquid (SFL) technologies were used to prepare powders of danazol/PVP K-15 in a 1:1 ratio. The evaporative precipitation into aqueous solution (EPAS) and SFL compositions, physical mixture and commercial product were dosed by oral gavage to 28 male Swiss/ICR mice for each arm of the study. Samples were taken at time points ranging from 0.5 to 24 h. Pooled mouse serum was analyzed for danazol by high performance liquid chromatography (HPLC). Powders were analyzed for their ability to form supersaturated solutions through dissolution at concentrations of 1 mg/mL which was the dose delivered to the mouse models. Spray freezing into liquid (SFL) and EPAS compositions displayed higher C(max) at 392.5 ng/mL and 430.1 ng/mL, respectively, compared to the physical mixture (204.4 ng/mL) and commercially available danazol (199.3 ng/mL). The T(max) for all compositions studied was near the 1 h time point. The area under the curve (AUC) for the SFL composition was 2558 ng.h/mL compared to EPAS composition at 1534 ng.h/mL. The area under the curve (AUC) for the physical mixture and commercially available danazol were 672 ng.h/mL and 1519 ng.h/mL, respectively. The elimination rate constants for the EPAS composition, SFL composition, and physical mixture were similar at approximately 0.15 h(-1) where as the commercially available danazol capsules displayed an elimination rate constant of 0.103 h(-1). The extent of danazol absorption in the mouse model was higher for SFL composition compared to the less amorphous EPAS composition, physical mixture, and commercially available danazol powders. Both EPAS and SFL compositions were able to form supersaturated solutions. However, the SFL composition displayed a supersaturation of 33% above control and was able to maintain supersaturation for 90 min compared to the EPAS composition (27% supersaturation above control for 60 min). Through the use of a testing method for supersaturation, it was found that EPAS and SFL compositions achieve higher apparent solubilities when compared to the physical mixture and commercially available danazol capsules. Because of the greater extent of dissolution of the SFL composition, the bioavailability was enhanced in a mouse model.     

Preparation and mesostructure control of highly ordered zirconia particles having crystalline walls

Mesostructured zirconia particles having monoclinic-type crystalline walls were prepared using a low-temperature crystallization technique. Crystalline zirconia particles with highly-ordered mesostructures were obtained through the sol–gel process of zirconium sulfate tetrahydrate at 333 K in the presence of molecular self-assemblies of cetyltrimethylammonium bromide (CTAB) or mixtures of CTAB and anionic molecules such as sodium dodecyl sulfate and sodium p-toluenesulfonate. Variations in the molar ratios of CTAB and the chemical species of anionic molecules led to the variations in the periods of highly-ordered zirconia having crystalline walls. Calcination of the mesostructured zirconia particles prepared using templates consisting solely of CTAB yielded crystalline mesoporous zirconia particles.     

Analytical light-scattering solution for Chebyshev particles

We develop a modification of the T-matrix method that allows for fast calculations of scattering properties of particles with irregular shapes. This modification uses the so-called Sh matrices, the elements of which depend on the shape of particles and do not depend on the particle size or optical constants; i.e., the introduction of Sh matrices makes possible the separation of these parameters within the T-matrix algorithm. For a given shape of a scattering object we calculate the Sh matrices only once and then can quickly calculate the T-matrix elements for a number of sizes and refractive indices. This, in particular, can provide rapid particle-size and refractive index averaging in a particle ensemble. This separation is useful for the derivation of an analytical light-scattering solution for Chebyshev particles.     

Relationship between crystallization temperature and melting temperature in crystalline materials

The ratio of the absolute temperature at which the homogeneous nucleation rate or the crystal growth rate is maximum (T _cmax) to the absolute melting temperature (T _m) is analysed by two parameters: one is the ratio of the activation energy for migration (E) and the heat of fusion (H _m), the other is the ratio of mean molar surface energy and H _m. In analysing the crystallization data for a large number of crystalline materials such as metals and inorganic, organic and polymeric materials, the ratios and E/H _m show roughly constant values for a given type of material. The constancy of the two parameters will then give rise to a constant value ofT _cmax/T _m.     

Nucleation and crystallization of solids from solution

Over the past couple of years, important insights into the problem of nucleation from solution on the theoretical as well as on the modeling side have been achieved. Experimentally, in situ techniques applied during the nucleation and the crystallization reaction are being developed, which will help to analyze the elementary processes during these reactions. A particularly active field was that of zeolite formation.     

Toughening of thermoset polymers by rigid crystalline particles

The toughening of an aromatic amine-cured diglycidyl ether of bisphenol-A epoxy with particles of crystalline polymers was studied. The crystalline polymers were poly (butylene terephthalate), nylon 6, and poly(vinylidene fluoride). Nylon 6 and poly(vinylidene fluoride) were found to toughen the epoxy about as well as did an equivalent amount of CTBN rubber. Poly(butylene terephthalate) was found to toughen the epoxy about twice as well as did the rubber. The toughness of poly(butylene terephthalate)-epoxy blends was independent of particle size for sizes in the range of tens of micrometres, but the toughness of the nylon 6-epoxy blends decreased with increasing particle size for sizes smaller than about 40 μm. There was no loss of either Young's modulus or yield strength of the epoxy with the inclusion of either nylon 6 or poly(butylene terephthalate) and less loss of these with the inclusion of poly(vinylidene fluoride) than with the inclusion of rubber. Toughness seems to have arisen from a combination of mechanisms. The poly(butylene terephthalate)-epoxy blends alone seem to have gained toughness from phase-transformation toughening. Crack path alteration and the formation of steps and welts and secondary crack bridging seem to have accounted for an especially large part of the fracture energy of the poly(vinylidene fluoride)-epoxy blends. Secondary crack nucleation contributed to the toughness of the nylon 6-epoxy blends.     

Production and characterization of plutonium dioxide particles as a quality control material for safeguards purposes

Plutonium (Pu) dioxide particles were produced from certified reference material (CRM) 136 solution (CRM 136-plutonium isotopic standard, New Brunswick Laboratory, Argonne, IL, U.S.A., 1987) using an atomizer system on December 3, 2009 after chemical separation of americium (Am) on October 27, 2009. The highest density of the size distribution of the particles obtained from 312 particles on a selected impactor stage was in the range of 0.7-0.8 μm. The flattening degree of 312 particles was also estimated. The isotopic composition of Pu and uranium (U) and the amount of Am were estimated by thermal ionization mass spectrometry (TIMS), inductively coupled plasma mass spectrometry (ICPMS), and α-spectrometry. Within uncertainties the isotopic composition of the produced particles is in agreement with the expected values, which were derived from the decay correction of the Pu isotopes in the CRM 136. The elemental ratio of Am to Pu in the produced particles was determined on the 317th and 674th day after Am separation, and the residual amount of Am in the solution was estimated. The analytical results of single particles by micro-Raman-scanning electron microscopy (SEM)-energy-dispersive X-ray spectrometry (EDX) indicate that the produced particles are Pu dioxide. Our initial attempts to measure the density of two single particles gave results with a spread value accompanied by a large uncertainty.     

Morphological control of ZnO particles synthesized via a new and facile aqueous solution route

Zinc oxide with a diversity of well-defined morphologies was synthesized via a simple aqueous solution route by decomposing Zn_xO_y(OH)_z precursor at suitable reaction conditions. Flower-like ZnO composed of rods was obtained by treating Zn_xO_y(OH)_z precursor in the reaction solution at 90 °C for 6 h. The precipitate of layer-like Zn_xO_y(OH)_z precursor was decomposed by drying at 90 °C for 24 h in air, resulting in the formation of ZnO microtubes.     

Non-equilibrium crystallization in freezing porous media: Numerical solution

The boundary value problem which arises during heat and moisture transfer in freezing fine-grained porous media under phase transition conditions is solved. It is assumed that the phase transition process occurs with finite rate of the water crystallization. So, the non-instantaneous kinetics is considered. Since the problem is significantly nonlinear the numerical method for the solution is applied. For the approximation of the system of differential equations the implicit two-level finite-difference scheme with central differences for space coordinate and one-side differences for time is used. The finite-difference system of equations is solved by “double sweep method.” It was shown the stability of “double sweep method” and solvability of the problem. Based on the correlation analysis, the dimensionless form for the diffusion coefficient as a function of moisture is obtained and used for the modeling. It is shown that the results for the characteristic distributions — temperature and total moisture, obtained in numerical solution, are in a good agreement with experimental investigations. The effect of the main criteria for the considered process — Lewis and Stefan numbers on the temperature, moisture, ice content and total moisture distributions is discussed. Especial attention was paid on the formation of the kinetic zone and its transformation in the course of non-equilibrium freezing. It was shown that the kinetic zone has a width of about 20–40% of the overall dimension of the system. Therefore the simulation of the phase transition zone as an infinitely thin front in freezing process, which is an approach incorporated in most theoretical models, is not suitable for the non-equilibrium water crystallization processes in fine-grained soils, and thereby conforms the validity of the kinetic approach.     

Preparation of stable micron-sized crystalline irbesartan particles for the enhancement of dissolution rate

Purpose: In this study, micron-sized crystalline drug particles of irbesartan (IBS) were prepared to improve its stability and dissolution rate.

Method: The approach to crystalline particles was based on the liquid precipitation process by which the amorphous particles were prepared. Pharmaceutical acceptable additives were used as the crystallization agent to convert the amorphous drug into crystalline particles. High pressure homogenization (HPH) process has been employed to reduce the size of the crystalline particles, and the micron-sized particles were obtained by the freeze-drying process.

Results: Different additives show different influences on the polymorphic form of IBS. Polyvinylpyrrolidone (PVP) and hydroxypropyl methylcellulose (HPMC) were effective in stabilizing amorphous particles instead of converting amorphous drug into crystalline particles, while poloxamer407 (F127) and tween80 (T80) could convert the amorphous drug into crystalline particles. T80 was also effective in controlling the particle size than that of F127. After HPH, crystalline particles with an average of 0.8 μm were obtained. The freeze-dried micron-sized crystalline particles exhibited significantly enhanced in vitro dissolution rate when compared to the raw drug. SEM, FT-IR, XRD, DSC and dissolution rate studies indicated that the micron-sized particles were stable during 6 months storage.

Conclusion: The preparation of micron-sized crystalline drug particles is an effective way to improve the stability and dissolution rate of irbesartan.     

Structural features and mechanism of crystallization of CuO ultrafine particles

The structural features and mechanism of crystallization of CuO ultrafine particles (200–450 nm) were, studied by transmission electron microscopy, as well as by thermal analyses (differential scanning calorimetry, thermogravimetric analysis, etc). The CuO ultrafine particles were not single crystals, but built up of subunits of much smaller size; between two of these subunits low-angle crystal boundaries exist. In the heating procedure, as the temperature increased, CuO ultrafine particles lost their absorbed and inclusive water gradually, the crystalline completeness was improved, and the temperature of crystallization was about 320 °C.     

超声波对脱气与未脱气氯化铵溶液结晶的影响

为了阐明超声波强化饱和溶液结晶的机理,分别研究了超声波对脱气饱和氯化铵溶液与未脱气饱和氯化铵溶液结晶的影响。结果显示,在相同超声波辐射下,脱气饱和氯化铵溶液与未脱气饱和氯化铵溶液的结晶均得到了强化,但未脱气饱和氯化铵溶液白浊化开始时间显著小于脱气饱和氯化铵溶液白浊化开始时间,未脱气氯化铵溶液结晶晶粒比脱气氯化铵溶液结晶晶粒更细小。这表明超声空化以及声场中溶液分子振动引起的能量、温度及密度的波动对饱和溶液的结晶均有影响,但空化是强化饱和溶液结晶的主要因素。     

Bioactivity study of glass-ceramics with various crystalline fractions obtained by controlled crystallization

Tests were performed “in vitro” in order to analyse the bioactivity of a glass-ceramic composition (soda–lime–silica glass). Samples of glass-ceramics with several crystallized fractions were controlled by crystallization. These glass-ceramics were exposed to a solution that simulates the fluid body obtained (SBF-K9) for 18 up to 200 h. The evolution of silica-gel layer, amorphous calcium phosphate and hydroxycarbonateapatite (HCA) formation was analysed using Fourier transform infrared spectroscopy (FTIR). All the glass-ceramics showed the formation of a well-developed HCA layer on its surface in less than 100 h of exposure time.