Studies on the encapsulation of oxymatrine into liposomes by ethanol injection and pH gradient method

Oxymatrine is the major active alkaloid constituent extracted from traditional Chinese herb medicine Sophora flavescens Ait (Kushen) and Sophora alopecuroides (Kudouzi). In recent years, oxymatrine had been found to posses remarkable anti-hepatic activity and has been used for treating hepatitis B in clinical therapy in China. In this study, we attempted to entrap oxymatrine into liposomes to facilitate the delivery of oxymatrine to the liver and enhance the therapeutic efficiency for hepatitis. Preformulation investigation was performed to obtain the drug physicochemical properties such as solubility, pKa, and logP for rational liposomes preparation design. Liposomes were prepared with soybean lecithin by ethanol injection and pH gradient loading methods. At the same time the factors affecting the entrapment efficiencies were investigated and compared. Ethanol injection method yielded liposomes with entrapment efficiency less than 20%. The lipid composition and aqueous medium had some effects on entrapment efficiency. However, liposomes could be produced with entrapment efficiency above 50% by pH gradient method. The internal pH buffer capacity, the lipid composition, and drug-to-lipid ratio greatly influenced the entrapment efficiency, while the incubation temperature had almost no effect on entrapment efficiency in the active loading procedure.     

Effect of pH, phosphate buffer concentration and the ionic strength on the stability of cefotetan disodium

The stability of cefotetan disodium between the pH range 2-8 has been studied using a stability-indicating HPLC assay method. The optimum pH range of stability appears to be 3.6-6.4. At pH 2 or 8, the decomposition was approximately 2 times faster than between pH 3.6-6.4. The HPLC method used is accurate and precise with percent relative standard deviation of 1.0 based on 5 readings. The decomposition of cefotetan followed first-order law. The K_h and K_oh values were estimated to be 3.8 and 4.4 × 10⁴ d^-1.     

Effect of pH,phosphate buffer concentration and the ionic strength on the stability of cefotetan disodium

Abstract

The stability of cefotetan disodium between the pH range 2-8 has been studied using a stability-indicating HPLC assay method. The optimum pH range of stability appears to be 3.6-6.4. At pH 2 or 8, the decomposition was approximately 2 times faster than between pH 3.6-6.4. The HPLC method used is accurate and precise with percent relative standard deviation of 1.0 based on 5 readings. The decomposition of cefotetan followed first-order law. The K_h and K_oh values were estimated to be 3.8 and 4.4 × 10⁴ d^-1.     

Improved crystallization characteristics of ZnO thin film grown onto a-C:H film used as a buffer layer

We employed a-C:H buffer layer to improve the crystalline property of ZnO thin film for the membrane film bulk acoustic resonator (FBAR). The a-C:H film as a buffer layer is prepared by applying dc bias of 200 V and also this sample showed a smoother surface roughness, higher hardness and Young's modulus when compared to the other samples. In addition, the FWHM value was improved from 7.5 to 4.3° on a-C:H film. The fabricated FBAR device showed the resistivity of 0.73 × 10⁸ Ω when compared with no buffer layer and the frequency characteristics of the FBAR were finally confirmed to be 1.15 GHz and 21.24 dB, respectively.     

Ag-TCNQ电双稳薄膜的疲劳和锻炼效应研究

用真空蒸法的方法制备了Ag-TCNQ电双稳薄膜.研究了在不同的电压作用下薄膜的阻抗转变规律.发现了阻抗转变过程中的疲劳和锻炼效应即用连续的高于阈值的窄电压脉冲作用于薄膜后,薄膜阻抗转变弛豫时间缩短;而用低于极限电压的脉冲连续作用于薄膜后,薄膜阻抗转变弛豫时间变长.从阻抗转变的能量效应出发,通过外电场的作用导致分子取向的弹性和塑性形变讨论了薄膜电阻跃迁的机理.     

Aluminum elution and precipitation in glass vials: effect of pH and buffer species

Inorganic extractables from glass vials may cause particle formation in the drug solution. In this study, the ability of eluting Al ion from borosilicate glass vials, and tendencies of precipitation containing Al were investigated using various pHs of phosphate, citrate, acetate and histidine buffer. Through heating, all of the buffers showed that Si and Al were eluted from glass vials in ratios almost the same as the composition of borosilicate glass, and the amounts of Al and Si from various buffer solutions at pH 7 were in the following order: citrate?>?phosphate?>?acetate?>?histidine. In addition, during storage after heating, the Al concentration at certain pHs of phosphate and acetate buffer solution decreased, suggesting the formation of particles containing Al. In citrate buffer, Al did not decrease in spite of the high elution amount. Considering that the solubility profile of aluminum oxide and the Al eluting profile of borosilicate glass were different, it is speculated that Al ion may be forced to leach into the buffer solution according to Si elution on the surface of glass vials. When Al ions were added to the buffer solutions, phosphate, acetate and histidine buffer showed a decrease of Al concentration during storage at a neutral range of pHs, indicating the formation of particles containing Al. In conclusion, it is suggested that phosphate buffer solution has higher possibility of forming particles containing Al than other buffer solutions.     

Study on thermal stability of electroless deposited Ni-Co-P alloy thin film

The Ni–P and Ni-Co-P alloy thin films were deposited on silicon substrates with electroless technique. The solid state metallurgical reactions were investigated with silicon for the viewpoint of Co co-deposition effect. The alloy film kept amorphous state with increasing Co content even though the P content decreased. The films become more amorphous, and the thermal stability increased with increment of Co content in the deposit. The Co content was varied from 11.013 to 45.068 wt% while P content was decreased from 9.340 to 6.491 wt% by varying the concentration of components in electroless deposition baths. The thermal stability was examined by X-ray diffractometer (XRD), four probe, and atomic force microscopy (AFM). The results indicated the Ni-Co-P alloy films with lower P content show the higher thermal stability then the ordinary Ni–P films and prevent the silicidation at low temperature because the Ni crystallization formation suppressed by the co-deposition of Co.     

Structural and optical properties of high quality ZnO thin film on Si with SiC buffer layer

ZnO thin films are grown on Si substrates with SiC buffer layer using ion plasma high frequency magnetron sputtering. These substrates are fabricated using a technique of solid phase epitaxy. With this technique SiC layer of thickness 20-200 nm had been grown on Si substrates consisting pores of sizes 0.5-5 μm at SiC and Si interface. Due to mismatching in lattice constants as well as thermal expansion coefficients, elastic stresses have been developed in ZnO film. Pores at the interface of SiC and Si are acting as the elastic stress reliever of the ZnO films making them strain free epitaxial. ZnO film grown on this especially fabricated Si substrate with SiC buffer layer exhibits excellent crystalline quality as characterized using X-ray diffraction. Surface topography of the film has been characterized using Atomic Force Microscopy as well as Scanning Electron Microscopy. Chemical compositions of the films have been analyzed using Energy Dispersive X-ray Spectroscopy. Optical properties of the films are investigated using Photoluminescence Spectroscopy which also shows good optical quality.     

Fabrication of GaN epitaxial thin film on InGaZnO4 single-crystalline buffer layer

Epitaxial (0001) films of GaN were grown on (111) YSZ substrates using single-crystalline InGaZnO₄ (sc-IGZO) lattice-matched buffer layers by molecular beam epitaxy with a NH₃ source. The epitaxial relationships are (0001)_GaN//(0001)_IGZO//(111)_YSZ in out-of-plane and [112¯0]_GaN//[112¯0]_IGZO//[11¯0]_YSZ in in-plane. This is different from those reported for GaN on many oxide crystals; the in-plane orientation of GaN crystal lattice is rotated by 30° with respect to those of oxide substrates except for ZnO. Although these GaN films showed relatively large tilting and twisting angles, which would be due to the reaction between GaN and IGZO, the GaN films grown on the sc-IGZO buffer layers exhibited stronger band-edge photoluminescence than GaN grown on a low-temperature GaN buffer layer.     

The effect of cluster size on thin film media noise

A dynamic micromagnetic model of thin film magnetic recording media with generalised structure has been used to study the effect of cluster size on thin film media noise. Clusters formed by common crystallography and by intergranular exchange coupling have been simulated, and the effects of clustering on hysteresis and noise are presented. For small clusters of a few grains, crystallographic correlations are shown to have the same effect on noise as intergranular exchange coupling, giving an increase in magnetic feature size and noise     

Induced effect of transparent substrate composition on polypyrrole thin film

For thin films of tin dioxide, indium oxide and indium tin oxide, the substrate nature plays a determining role on their structural and morphological characteristics, which modified noticeably their optical property. On these substrates, the electropolymerization characteristics of polypyrrole exhibited the profound modifications related to the active sites for nuclei formation and their growth. These modifications induced the important change in charge transport characteristics of polypyrrole thin films.     

Role of atomic migration in nanocrystalline stability: Grain size and thin film stress states

As the length scale of materials decreases to the nanometer regime, grain boundaries occupy a relatively larger volume fraction. Consequently, they play an important role in stabilizing nanocrystalline systems. This review looks at the role of solute segregation to grain boundaries in stabilizing such systems. In recent years, grain size stabilization from solute segregation has led to new types of thermodynamic stability maps as a materials design tool. We propose to extend and adapt these concepts of grain boundary solute segregation as a stabilizing effect to thin film stress states. A recent study on Fe–Pt alloy films, where one species enriched the boundaries, was shown to manipulate the stress from tensile-to-compressive as a function of composition. This suggests that intrinsic segregation can be used as a tunable variable to manipulate stress states, analogous to changing film processing parameters, such as deposition rate and pressure. The application of such solute segregation is at the precipice of new opportunities in materials design of thin films.     

Investigation of thermal stability of Mo thin-films as the buffer layer and various Cu metallization as interconnection materials for thin film transistor-liquid crystal display applications

Cu/Mo/Si multi-layer structures were fabricated to investigate diffusion behaviors and thermal stability between Cu and Mo. Physical vapor deposition (PVD), chemical vapor deposition, electroplating and electrolessplating were used to grow 100 nm thick Cu films as interconnection materials, and radio-frequency sputtering system was introduced to grow 37.5 nm thick Mo films as a buffer layer. All Cu/Mo/Si multi-layer specimens were annealed at 350 to 700 °C for 30 min. When the annealing temperature was over 600 °C, the Cu diffused through Mo into Si, and the Cu₃Si phase and Mo-Si intermetallic compounds formed at the Mo/Si interface. The diffusion mechanism is the grain boundary diffusion. The results indicate that Cu film deposited by PVD had best crystallinity, lower roughness, large adhesive energy and resistivity. The values of the resistivity, diffusion activity energy and large adhesive energy are 5.47 μΩ-cm, 0.948 eV and 2.46 N/m, respectively.     

Synthesis of CdZnS buffer layer and its impact on Cu2ZnSn(S,Se)4 thin film solar cells

Journal of Materials Science: Materials in Electronics - CdZnS thin films with low zinc content were deposited by a chemical bath deposition method. The structural and the optical properties of the...     

Suppression of pH effect on the electrochemical deformation in polyaniline film

pH effect on the electrochemical deformation of freestanding polyaniline (PANi) film was investigated by means of electrochemomechanical deformation (ECMD) measurement. The maximum anodic expansion was found in PANi at around pH = 1.5 in aqueous acid consisted of HCl and NaCl. The deformation vs. redox charge (D−Q) plots revealed the critical differences in the deformation characteristics below and above pH = 1.5. The similar pH dependences were also observed in other acidic media. Against these results, we investigated the surface coating effect of PANi film on deformation behaviors. It was revealed that the PPy coating on PANi film successfully reduced the pH dependence of the PANi/PPy film deformation. The results indicate that the buffer layer coated on the PANi film surface decreases the ion concentration effects on the PANi deformation. The result indicates the extensive usage of PANi actuator in wide pH aqueous media.     

IN2S3:Ag, an ideal buffer layer for thin film solar cells

Silver diffusion enhanced the properties of Indium sulfide (In₂S₃) films making it highly suitable buffer layer for photovoltaic applications. Thin layer of silver deposited over In₂S₃ films diffused into In₂S₃ films in ‘as-deposited’ condition itself creating doping effect. A significant enhancement in crystallinity and grain size could be obtained up to an optimum percentage of doping concentration. This optimum value showed dependence on thickness and atomic ratio of indium and sulfur in the film. Band gap decreased up to the optimum value of doping and thereafter it increased. Electrical studies showed a decrease in resistivity due to doping. Sample having the optimum doping was found to be more photosensitive and low resistive when compared with the pristine sample. These results proved that silver diffused indium sulfide surpasses pristine sample for crystallinity and photosensitivity. Doping β-In₂S₃ film with optimum amount of silver modified the structural and electrical properties of the films favorably so that the Ag electrodes given to the ITO/CuInS₂/In₂S₃ cell structure itself acted as a doping agent for the In₂S₃ layer, enhancing the cell efficiency to 9.5% (John et al. Sol Energy Mater Sol Cells 89:27, 2005).     

Hydrogen effect on fracture toughness of thin film/substrate interfaces

The effect of hydrogen on the interface fracture toughness of two nano-film/substrate structures, Ni/Si and Cu/Si, were evaluated using four-point bend specimens with and without hydrogen charging. Hydrogen typically decreases the fracture toughness of materials. However, we found in this study that the interfacial toughness between the Ni film and the Si substrate increased due to the presence of hydrogen, while that of Cu/Si decreased. Nanoindentation experiments for the Ni and Cu films revealed that local plasticity in the Ni and Cu films is promoted by the charged hydrogen. The critical stress intensity at the Ni/Si interface crack considering the plasticity of Ni, namely the true fracture toughness, is scarcely influenced by the existence of hydrogen. The apparent increase in fracture toughness of the Ni/Si interface is due to the large stress relaxation near the crack tip caused by softening due to the presence of hydrogen. Although the promotion of plastic deformation of Cu relaxes the stress intensity at the Cu/Si interface crack, the apparent interfacial toughness still decreases because of the significant decrease in the true toughness due to the presence of hydrogen.     

Solvent effect on the thin film formation of polymeric solar cells

This research work investigates the influence of the solvent used upon the formation of polymeric photoactive layer. This photoactive layer consists of a blend of poly (3-hexylthiophene) (P3HT) and [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM), to produce P3HT:PCBM (at 1:1 ratio) blend thin films, in which the material solutions are deposited onto clean substrates via spin-coating technique. Three types of solvents were used namely: 100% dichlorobenzene (DCB), 100% chloroform (CH) and 50%:50% mixture of DCB and chloroform. The results reveal that the mixture of solvent produces a better solubility of the polymeric materials compared to that of the pure single solvent.     

Effects of elastic anisotropy on the surface stability of thin film/substrate system

The surface stability of thin film/substrate system is an important problem both in the film synthesis and reliability of micro electrical and mechanical system (MEMS). In this work, the elastic anisotropy effect on surface stability of thin film/substrate system was considered. The theoretical analysis indicates that elastic anisotropic influence could play an important role in the surface stability of thin film/substrate system. And the anisotropy effect should be considered both in the thin film synthesis process and its service reliability. In addition, there exists an nondimensional parameter k for cubic crystalline thin film materials in evaluating the anisotropic effect. When k is larger than one unit, the surface stability will be weakened by anisotropic effect; vice versa. The method used in present work could be easy extended to multi-layered thin film/substrate system and help us to consider the elastic anisotropy effect.