环氧化聚异丁烯合成新工艺的研究

研究了采用间氯过氧苯甲酸(MCPBA)为氧化剂,由高活性聚异丁烯(HRPIB)制备环氧化聚异丁烯(EPIB)的新工艺。考察了反应温度、反应时间及原料双键与MCPBA摩尔配比对环氧化物的环氧值的影响。实验确定了PIB环氧化反应的适宜工艺条件:反应温度为30℃,反应时间为2h,双键与MCPBA的摩尔比为1∶1.3,在此条件下,环氧值为0.7887;红外光谱和核磁分析证明了所制备的产物为目标产物。该产品无色粘稠,将应用于橡胶改性、树脂改性领域。     

Influence of metronidazole particle properties on granules prepared in a high-shear mixer-granulator

Metronidazole is a good example of high-dose drug substance with poor granulating and tableting properties. Tablets are generally produced by liquid granulation; however, the technological process failure is quite frequent. In order to verify how the metronidazole particle characteristics can influence granule properties, three metronidazole batches differing for crystal habit, mean particle size, BET surface area and wettability were selected, primarily designed according to their different elongation ratio: needle-shaped, stick-shaped, and isodimensional. In the presence of lactose monohydrate and pregelatinized maize starch, respectively as diluent and binder, they were included in a formula for wet granulation in a high-shear mixer-granulator. In order to render the process comparable as far as possible, all parameters and experimental conditions were maintained constant. Four granule batches were obtained: granules from placebo (G-placebo), granules from needle-shaped crystals (G-needle-shaped), granules from stick-shaped crystals (G-stick-shaped), and granules from isodimensional crystals (G-isodimensional). Different granule properties were considered, in particular concerning porosity, friability, loss on drying (LOD), and flowability. In order to study their tabletability and compressibility, the different granules obtained were then compressed in a rotary press. The best tabletability was obtained with the isodimensional batch, while the poorest was exhibited by the stick-shaped one. Differences in tabletability are in good accordance with compressibility results: to a better tabletability corresponds an important granule ability to undergo a volume reduction as a result of an applied pressure. In particular, it was proposed that the greatest compressibility of the G-isodimensional must be related to the greatest granule porosity percentage.     

Carbopol-gelatin coacervation and drug microencapsulation

Abstract

Carbopol-gelatin coacervates were recovered as water-insoluble powder which when suspended in water gave a highly disperse system.

Glycerol as a protective against coacervate deformation, formaldhyde as a denaturant and some monohydric aliphatic alcohols as flocculating agents were variables studied. The hypothesis that solid particles may be protectively encapsulated by coacervation led to the investigation of the encapsulation of sulfadiazine at four coat-core ratios. The surface-adhering drug as well as the percentage of drug in the microcapsule increased on raising the core ratio. The size distribution was determined by use of standard sieves and the influence of four coat/core ratios was noted. Availability studies show that sulphadiazine was readily accessable to the leaching effect of the artifical intestinal fluids.     

Carbopol-gelatin coacervation and drug microencapsulation

Carbopol-gelatin coacervates were recovered as water-insoluble powder which when suspended in water gave a highly disperse system.

Glycerol as a protective against coacervate deformation, formaldhyde as a denaturant and some monohydric aliphatic alcohols as flocculating agents were variables studied. The hypothesis that solid particles may be protectively encapsulated by coacervation led to the investigation of the encapsulation of sulfadiazine at four coat-core ratios. The surface-adhering drug as well as the percentage of drug in the microcapsule increased on raising the core ratio. The size distribution was determined by use of standard sieves and the influence of four coat/core ratios was noted. Availability studies show that sulphadiazine was readily accessable to the leaching effect of the artifical intestinal fluids.     

微胶囊技术在纺织行业中的应用

介绍了国内外微胶囊在纺织品染色、印花和化学后整理的发展近况、应用及前景     

Synthesis and characterization of antioxidants and detergent dispersant based on some polyisobutylene copolymers

Polyisobutylene succinic anhydride-urea/polyamines (PIBSA) copolymers were synthesized as potential antioxidants and detergent dispersant agents for lubricating oils samples (SAE-30). Homogeneity, thermal stability and dispersancy of the solutions were determined. Fully soluble oil compounds that are thermally stable up to 250 °C were achieved. The oxidation stability of lube oil samples in the presence of four designed PIBSA additives (varying in the number of amine groups) was determined for a time period of up to 72 hours. The dependence of the additive efficiency on its concentration was studied to achieve maximum stability. Some PIBSA additives at concentration 3.0 · 10⁴ ppm exhibit the best results. Dispersivity values were measured at predetermined oxidation times. The results proved reliable dispersion capability as the nitrogen content of the additive is increased, i.e. the increase in the basic character of the additive leads to the increase in the neutralization capability. Moreover, the designed PIBSA additives retain their efficiency after long oxidation times, confirming their role as multifunctional nitrogen containing polymeric additive. Electronic Publication     

Natural polymers for the microencapsulation of cells

The encapsulation of living mammalian cells within a semi-permeable hydrogel matrix is an attractive procedure for many biomedical and biotechnological applications, such as xenotransplantation, maintenance of stem cell phenotype and bioprinting of three-dimensional scaffolds for tissue engineering and regenerative medicine. In this review, we focus on naturally derived polymers that can form hydrogels under mild conditions and that are thus capable of entrapping cells within controlled volumes. Our emphasis will be on polysaccharides and proteins, including agarose, alginate, carrageenan, chitosan, gellan gum, hyaluronic acid, collagen, elastin, gelatin, fibrin and silk fibroin. We also discuss the technologies commonly employed to encapsulate cells in these hydrogels, with particular attention on microencapsulation.     

Methoxybutropate microencapsulation by gelatin-acacia complex coacervation

Microcapsules of methoxybutropate solid particles or of an oily saturated solution of the same drug were prepared by complex coacervation between gelatin and acacia and dried with three different methods: isopropanol addition, spray-drying, and freeze-drying. Successively, microparticles were analyzed by infrared thermobalance, ultraviolet (UV) spectroscopy, optical and scanning electron microscopy, and sieves to find out parameters such as yield, moisture content, encapsulation percentage, morphology of solid particles, and particle size. Results highlighted that the most appropriate drying method for industrial purposes was spray-drying, particularly for oil-containing microcapsule formulations.     

Isotactic polypropylene/polyisobutylene blends: morphology-structure-mechanical properties relationships

Morphological observations by optical and scanning electron microscopy, wide (WAXS) and small (SAXS) angle X-ray scattering, differential scanning calorimetry (DSC) and mechanical tests have been performed on sheet specimens of isotactic polypropylene (iPP)/polyisobutylene (PIB) blends obtained under different crystallization conditions. Two kinds of morphologies have been observed, particularly at high crystallization temperatureT _c, on thin sections of the same sheets: a spherulitic one in the centre and a row-like structure on the edges. The size of the spherulites, as well as the thickness of the row-like regions, decreases with diminishingT _c, and seemsto be independent of the amount of rubber. The adhesion among the spherulites and between the spherulites and the row-like regions seems to become poorer with higherT _c. The rubber particles seem to be evenly dispersed into the iPP matrix for samples quenched at low temperatures, whereas for samples isothermally crystallized (at highT _c) their concentration seems to be slightly higher at the border of the spherulites than in the centre. The overall crystallinity measured by DSC and by WAXS is an increasing function ofT _c and decreases with increasing amount of PIB. The index of iPP phase, quite low indeed (max 3%), drops with loweringT _c and with enhancing PIB percentage. The long spacingL for a given quenching temperatureT _q is independent of PIB content, whereas for isothermally crystallized samples at low undercooling varies differently according toT _c. The lamellar thicknessL _c is always a decreasing function of rubber content. Stress-strain analysis shows a more and more brittle behaviour both with increasingT _c (beyondT _c=122° C all the specimens are very brittle irrespective of PIB amount) and PIB amount in accordance with the morphological observations. Some tentative hypotheses have been made to explain the observed behaviour.     

Solubility of core materials in aqueous polymeric solution effect on microencapsulation of curcumin

Curcumin, the main active constituent of turmeric herb (Curcuma longa L.) have been reported to possess many medicinal values. The application of curcumin in dermatological preparations is limited by their intense yellow color property, which stains the fabric and skin. The objectives of this study were to reduce the color staining effect and enhance the stability of curcumin via microencapsulation using gelatin simple coacervation method. As for curcumin, ethanol and acetone were used as coacervating solvents. Curcumin was dispersed in ethanol while dissolved in acetone. Irrespective of the types of coacervating solvents used, microencapsulation resolved the color-staining problem and enhanced the flow properties and photo-stability of curcumin. Nevertheless, it was found that more spherical curcumin microcapsules with higher yield, higher curcumin loading, and higher entrapment efficiency were obtained with acetone than ethanol. The in vitro release of curcumin after microencapsulation was slightly prolonged. Further evaluation of the effects of solubility of core materials in coacervating solvent or polymeric aqueous solution using six different drug compounds, namely, ketoconazole, ketoprofen, magnesium stearate, pseudoephedrine HCl, diclofenac sodium, and paracetamol, suggested that the solubility of core materials in aqueous polymeric solution determined the successful formation of microcapsules. Microcapsules could only be formed if the core materials were not dissolved in the aqueous polymeric solution while the core materials could either be dissolved or dispersed in the coacervating solvent. In summary, microencapsulation not only circumvents the color-staining problem but also improved the stability and flowability of curcumin. The solubility of core material in aqueous polymeric solution plays a pivotal role in determining the successful formation of microcapsules.     

混合C4制备高活性聚异丁烯技术进展

讨论了国内外以混合C<,4>为原料制备高活性聚异丁烯(HRPIB)的聚合技术进展.重点论述了不同催化体系下的HRPIB制备技术,如经典的BF<,3>系复合催化体系、新型钛系催化体系、新型铝系复合催化体系以及其它的催化体系,并介绍了一些合适的混合C<,4>原料组成.     

Latent imidazole curing agents by microencapsulation with copolymers

The encapsulation of imidazoles was conducted to prepare the latent imidazole curing agents by using the copolymers as the wall materials. The latent imidazole curing agents are essential to manufacturing anisotropic conducting films (ACFs). The copolymers, which were used for the encapsulation, were the copolymers of methacrylic acid (MAA) and octadecyl methacrylate (ODMA). The method for encapsulation was the spray-drying method. The curing behaviors of the microcapsules to epoxy resin were investigated using a differential scanning calorimeter (DSC). Using the encapsulated microcapsules, the curing reaction to epoxy resin was conducted at 150°C and 180°C, and the curing time was measured. The fabricated microcapsules using the copolymers showed an improved latent character compared with the previously reported results.     

Effect of process variables on the microencapsulation of vitamin A palmitate by gelatin-acacia coacervation

Microcapsules of vitamin A palmitate were prepared by gelatin-acacia complex coacervation. The effects of colloid mixing ratio, core-to-wall ratio, hardening agent, concentration of core solution, and drying method on the coacervation process and the properties of the microcapsules were investigated. The microcapsules of vitamin A palmitate were prepared using different weight ratios of gelatin and acacia, that is, 2:3, 1:1, and 3:2 under controlled conditions. The other factors studied were 1:1, 1:2, and 1:3 core-to-wall ratios; 30, 60, and 120 min of hardening time; 2, 5, and 10 ml of formaldehyde per 280 g of coacervation system as a hardening agent; and 30%, 40%, and 50% w/w vitamin A palmitate in corn oil as a core material. The drying methods used were air drying, hot air at 40°C, and freeze-drying. The results showed that spherical microcapsules were obtained for all conditions except for 30 min of hardening time, which did not result in microcapsules. The optimum conditions for free-flowing microcapsules with a high percentage of entrapped drug were 1:1 gelatin-to-acacia ratio and 1:2 core-to-wall ratio when hardening with 2 ml formaldehyde for 60 min and using 40% w/w vitamin A palmitate in corn oil as the core concentration. In addition, drying the microcapsules by freeze-drying provided microcapsules with excellent appearance.     

Characterization of various deformable liposomes with metronidazole

Objective: The aim of this study was to investigate various deformable liposomes for their potential application for the vaginal administration of metronidazole.

Materials and methods: Deformable liposomes composed of egg phosphatidylcholine (EPC) and various surfactants [sodium deoxycholate (SDCh), Tween 80 or Span 80] and conventional liposomes consisting of EPC and egg phosphatidylglycerol-sodium (EPG-Na) were prepared with and without metronidazole. Additionally, a freeze-thaw method was applied to both classes of vesicles (liposomes) containing the drug to improve its trapping capacity. All of the liposomes prepared were characterized and compared in terms of size, polydispersity, zeta potential, entrapment efficiency and their permeability on a Caco-2 cell monolayer.

Results and discussion: Conventional liposomes, both with and without metronidazole, were larger than the deformable vesicles. The presence of ethanol in the preparations of the elastic EPC/SDCh and EPC/Tween 80 liposomes was found to affect the particle size in terms of reducing this parameter. Different types of vesicles were compared for their trapping efficiency of metronidazole and the highest entrapment was observed with conventional liposomes. However, deformable EPC/SDCh liposomes were found to enhance the permeability of metronidazole more effectively than the conventional liposomes based on the in vitro model of the epithelial barrier.

Conclusion: These preliminary data indicate that EPC/SDCh liposomes may have a promising future in vaginal delivery of metronidazole. Therefore, additional investigations on elastic vesicles and their incorporation in a suitable vehicle should be considered to further evaluate their applicability in vaginal drug delivery.     

Effect of sodium bicarbonate on the properties of metronidazole floating matrix tablets

The effect of sodium bicarbonate (SB) on the swelling behavior and the sustained release of floating systems was studied with varied proportions of this excipient and metronidazole. Two polymers with different hydration characteristics, Methocel K4M and Carbopol 971P NF, were used to formulate the matrices. Under in vitro dissolution conditions, the addition of SB to metronidazole sustained-release tablets modifies the matrix hydration volume, increasing at the beginning, reaching a maximum, and then declining. Pure Carbopol matrices show a rapid hydration with a limited further effect of the SB and metronidazole loads. Methocel show a significant increase of the apparent hydration volume due to SB addition with no further notable change due to metronidazole load. Increasing the metronidazole load reduces the floating time of Carbopol matrices while no effect on Methocel matrices could be observed within 8 hours dissolution. Matrices show increasing release constant values (k) as the metronidazole load increases. Methocel matrices release the drug 10% to 15% faster than Carbopol matrices. SB increases the cumulative amount of drug released from Methocel but not that releasing from Carbopol. These results are attributed to the intrinsic polymer properties, the barrier effect of CO₂ bubbles, and the matrix volume expansion produced after addition of SB.     

炭黑/TiO2双粒子电泳分散体系中聚异丁烯的稳定作用

以纳米炭黑和TiO2 作为显示粒子,以四氯乙烯为分散介质制备电泳显示分散体系,研究了聚异丁烯对分散体系的稳定作用.结果表明,在12%(质童分数)的聚异丁烯存在下,能稳定地得到含童为10.38%(质量分数)的电泳粒子分散体系.该分散液在10-60℃的范围内保持粒子的平均粒径无变化;用该分散液制备的电泳显示器件表现了优异的...     

Integrating phase change materials into concrete through microencapsulation using cenospheres

Phase change materials (PCMs) can enhance the building energy efficiency through thermal energy storage and thermal regulation. Microencapsulated PCMs (MEPCMs) provide a better utilization of PCMs with building materials. This study proposes a novel method to encapsulate PCMs into cenospheres which are hollow fly ash particles generated in coal burning power plants with size ranging from a few micrometers to hundreds of micrometers. The shell of the cenosphere inherently has some small pores which are sealed by a thin layer of glass-crystalline film. By removing this film through chemical etching, these holes can be exposed, providing paths for PCMs moving into the internal void of cenospheres. A thin layer of silica is coated on the PCM loaded cenospheres to prevent the possible leakage of liquid PCMs. The produced PCM microcapsules are referred to as CenoPCM, which can be directly added into traditional construction and building materials such as concrete to produce thermally active concrete. Prototype thermally active cement mortar integrated with the produced CenoPCM capsules have also been manufactured and characterized for its mechanical and microstructural properties. The characterizations showed that there was only minor reduction in strength and the mortar remained strong enough for building application. From this work, it is found that the produced CenoPCM capsules have great potential to be added into construction materials for reducing energy consumptions in buildings.     

Erythrocytes as carriers of metronidazole: In-vitro characterization

Abstract

Rat erythrocytes were loaded with metronidazole by a method based on hypotonic preswelling, hemolysis, isotonic resealing and reannealing. The encapsulation efficiency of 42-56% was achieved. The loaded cells exhibited elevated osmotic fragility and lower resistance to turbulence shock as compared to the normal cells and were found to release encapsulated drug slowly. The glutaraldehyde treatment of the cells resulted in the stabilization of loaded cells, which were found to be highly resistant to the osmotic and turbulence shocks. In-vitro release of metronidazole was also retarded upon treatment, and was dependent upon the concentration of glutaraldehyde. The loaded erythrocytes were obtained in powder form, ready for reconstitution, with a view to improve the shelf life. On the basis of in-vitro studies glutaraldehyde treated erythrocytes appeared to be promising carriers of metronidazole.