Microencapsulation of bovine hemoglobin with high bio-activity and high entrapment efficiency using a W/O/W double emulsion technique

This study focused on the influences of solvent removal method and wall polymer composition on microspheres characteristics in W/O/W double emulsion procedure. Monomethoxypoly(ethylene glycol)-b-poly- -lactide (PELA) microspheres containing bovine hemoglobin (BHb, a model protein) were prepared by four solvent removal methods, including solvent-evaporation at atmosphere, at reduced pressure, solvent-extraction and solvent-diffusion methods, where the last method used ethyl acetate (EA) as organic solvent and the others used methylene chloride (MC). The bio-activity of encapsulated BHb, encapsulation efficiency, particle size and surface morphology of microspheres were evaluated in relation to the influences of solvent removal method and PELA composition. BHb encapsulated by the W/O/W double emulsion–solvent diffusion method with EA as organic solvent displayed a bio-activity near to that of native BHb. The efficiency of BHb entrapment achieved by this method was much higher than those by other methods (ca. 90% versus 30%). When using this process, the copolymers with MPEG 2000 block (molecular weight of PEG block: 2000 g/mol) yielded much higher efficiencies of BHb entrapment than those with MPEG 5000 block (90% versus 36%). Copolymer composition had less impact on microsphere size, but had a pronounced effect on surface morphology of microspheres. This study suggests that the W/O/W double emulsion–solvent diffusion method with EA as organic solvent is an effective process to prepare microspheres containing therapeutic proteins, and that the PELA copolymers containing MPEG 2000 block are promising wall material for biodegradable microsphere protein delivery system.     

Preparation of uniform-sized pH-sensitive quaternized chitosan microsphere by combining membrane emulsification technique and thermal-gelation method

In this study, uniform-sized pH-sensitive quaternized chitosan microsphere was prepared by combining Shirasu porous glass (SPG) membrane emulsification technique and a novel thermal-gelation method. In this preparation process, the mixture of quaternized chitosan solution and alpha-beta-glycerophosphate (alpha-beta-GP) was used as water phase and dispersed in oil phase to form uniform W/O emulsion by SPG membrane emulsification technique. The droplets solidified into microspheres at 37 degrees C by thermal-gelation method. The whole process was simple and mild. The influence of process conditions on the property of prepared microspheres was investigated and the optimized preparation condition was obtained. As a result, the coefficient of variation (C.V.) of obtained microspheres diameters was below 15%. The obtained microsphere had porous structure and showed apparent pH-sensitivity. It dissolved rapidly in acid solution (pH 5) and kept stable in neutral solution (pH 7.4). The pH-sensitivity of microspheres also affected its drug release behavior. Bovine serum albumin (BSA) as a model drug was encapsulated in microspheres, and it was released rapidly in acid solution and slowly in neutral medium. The novel quaternized chitosan microspheres with pH-sensitivity can be used as drug delivery system in the biomedical field, such as tumor-targeted drug carrier.     

Fat crystals: A tool to inhibit molecular transport in W/O/W double emulsions

Water-in-oil-in-water (W/O/W) double emulsions are a promising technology for encapsulation applications of water soluble compounds with respect to functional food systems. Yet molecular transport through the oil phase is a well-known problem for liquid oil-based double emulsions. The influence of network crystallization in the oil phase of W/O/W globules was evaluated by NMR and laser light scattering experiments on both a liquid oil-based double emulsion and a solid fat-based double emulsion. Water transport was assessed by low-resolution NMR diffusometry and by an osmotically induced swelling or shrinking experiment, whereas manganese ion permeation was followed by means of T₂-relaxometry. The solid fat-based W/O/W globules contained a crystal network with about 80% solid fat. This W/O/W emulsion showed a reduced molecular water exchange and a slower manganese ion influx in the considered time frame, whereas its globule size remained stable under the applied osmotic gradients. The reduced permeability of the oil phase is assumed to be caused by the increased tortuosity of the diffusive path imposed by the crystal network. This solid network also provided mechanical strength to the W/O/W globules to counteract the applied osmotic forces.     

Biocompatible microspheres based on acetylated polysaccharide prepared from water-in-oil-in-water (W1/O/W2) double-emulsion method for delivery of type II diabetic drug (exenatide)

Polysaccharide microspheres (PAMs) from acetylated pullulan were designed for the long-term delivery of peptide/protein drugs, as an alternative to a PLGA depot system. Three kinds of samples were obtained according to their different degrees of acetylation (0.8(PA1), 1.5(PA2), 2.3(PA3) acetyl groups in one glucose unit in pullulan), and then utilized to prepare a microsphere via a water-in-oil-in-water (W₁/O/W₂) emulsion method. The mean particle size of PAMs was shown to be in a range between 35 and 110 μm, as determined by a particle size analyzer. In order to evaluate their potential as a depot for protein/peptide delivery, exenatide, a drug used for the treatment of type II diabetes, was employed. The encapsulation efficiency of exenatide in PAMs was 69.1%, 80.4%, and 90.3% in PAM 1, PAM 2, and PAM 3, respectively. Although the release of exenatide from the PLGA microspheres evidenced a fast and high-burst behavior, PAMs evidenced a sustained release profile for 21 days. After 16 days, the released peptide was found to have a molecular weight almost identical to that of native exenatide, indicating that the stability of the peptide in the PAMs was maintained. The tissue reaction evidenced by the PAM was characterized by minimal foreign body reaction and minimal configurations of immune cells such as neutrophils and macrophages, but that of the PLGA microspheres was characterized by relatively elevated inflammation. On the basis of these results, we have concluded that the PAM may provide new insights into the development of new protein/peptide depots in long-term delivery.     

Control of heterogeneous structure of porous polymer microspheres prepared from polymerization system and preformed polymer system

The studies on control of heterogeneous structure of porous polymer microspheres prepared for suspension polymerization system and preformed polymer system in author’s research group were reviewed. Firstly, the phase-separation behavior in O/W suspension polymerization system for preparation of porous poly(divinylbenzene) microspheres was quantitatively studied by combining transmittance and gelation point measurement, from which the morphology can be manipulated. The same method can be employed to study the pore size control in W/O hydrophilic polymerization system. Because the simple porous microsphere could not satisfy new applications, we developed new methods to prepare gigaporous microsphere, which possessed much larger pores than those obtained by general diluents, for chromatographic separation media, as well as hollow-porous microsphere for construction of cell-like microreactor. Furthermore, in order to overcome the difficulty of heterogeneous structure control for preformed polymer system, we developed special methods to obtain porous, hollow-porous, and hollow chitosan microspheres. Finally, some application results by utilizing special morphologies were introduced.     

聚己二酸丁二酯纳米纤维构建的微球的制备

建立了采用异相成核和可控水解相结合的方法制备由纳米纤维构建的聚合物微球的新方法.根据多取代卞叉山梨醇(TM6)对聚己二酸丁二酯(PBA)的异相成核作用以及结晶形态的影响,采用两种乳液溶剂挥发法、并在聚合物溶液中加入成核剂TM6制备了PBA微球,研究了成核剂含量对PBA微球在酶促降解之后形态变化的影响.研究结果表明,二次乳液溶剂挥发法可以制备具有多孔结构的PBA微球,这种多孔结构有利于酶溶液进入到微球内部,促进PBA微球的均匀水解,最终获得由PBA纳米纤维构建的微球.当TM6的含量为3 wt%时,采用二次乳液溶剂挥发法制备的PBA微球,经过5 h酶促降解处理,可以得到表面和内部由PBA纳米纤维均匀组成的微球.进一步的细胞实验表明,微球的纳米纤维结构,有利于MG-63细胞在聚合物微球上的黏附、铺展和向内生长.     

催化剂对乳液模板法制备碳材料形貌的影响

以液体石蜡为油相,间苯二酚和甲醛的水溶液为水相,吐温80和司班80为乳化剂,获得油/水(O/W)型乳状液.将该乳状液聚合、碳化去除模板后制得了碳材料,研究了不同催化剂对所得碳材料形貌的影响.结果表明:选择NaOH为催化剂时,制得的碳材料是一种具有孔壁和孔洞的多孔碳泡沫,典型样品的孔径约为1-2μm;当氨水为催化剂时,所得碳材料是由微球或者相互缠绕的蠕虫状粒子组成的块体材料,这些微球或粒子的直径主要集中在1-2μm,与NaOH为催化剂时所得碳泡沫的孔径尺寸相当.研究发现,氨水的加入使得乳液体系发生了相转化,由原来的O/W型乳液逐渐转变为W/O型高内相乳液.从分子间氢键出发,应用内聚能理论探讨了催化剂导致的乳液相变以及不同形貌碳材料的形成过程.     

Preparations and properties of amino acid/dodecylamine/ibuprofen/H2O vesicles and microspheres

Stable vesicles and microspheres are directly prepared in amino acid/dodecylamine (DA)/ibuprofen/H₂O system. Vesicle can be automatically formed in glycine/DA/H₂O system. No vesicle and microsphere are found in l-glutamic acid or l-histidine/DA/H₂O systems. When ibuprofen is added into amino acid/DA/H₂O system, vesicles and microspheres can be formed and coexisted. Ibuprofen can regulate the quantity ratios between the vesicles and the microspheres. The structure properties of amino acid affect on the stabilities of the vesicles and microspheres. The formation mechanisms of the vesicles and microspheres are also discussed in this paper.     

瞬时离子释放扩散模型及熔盐电解固态WS_2制备纳米W的液相扩散研究

固态化合物熔盐电解冶金在21世纪初被提出后受到学术界和工业界的广泛关注.根据固态化合物电解的动态三相电化学界线模型,固态金属氧(硫)化物阴极在电解还原过程中,涉及O2?(S2?)在电解生成的多孔金属层中的液相扩散,但由于一直以来缺乏方便可靠的理论和实验方法,相关传质过程动力学的研究鲜有文献报道.本文引入多孔电极瞬时离子释放扩散模型,以粉末微腔电极为微型多孔电极,设计双电势阶跃实验研究了WS2在等摩尔比NaCl+KCl熔盐中电解时固态阴极中的液相扩散.实验结果与理论模型符合良好,973 K时,硫离子在孔隙率为69%的多孔金属钨层中的扩散系数为0.92×10?5 cm2/s,扩散活化能为53.4 kJ/mol.研究表明,二硫化钨在NaCl+KCl混盐体系中能够快速电解还原生成纳米金属钨,其中,S2?的扩散传质是整个电解过程的速度控制步骤.     

The delayed crosslinking amphiphilic polymer gel system based on multiple emulsion for in-depth profile control

Delayed crosslinking polymer gel systems are widely used in-depth profile control technology for water production control. In this paper, an amphiphilic polymer P(AM-NaA-DDAM) was synthesized by a free radical micellar polymerization method and a delayed crosslinking amphiphilic polymer gel system was prepared based on multiple emulsion of W₁/O/W₂ emulsion which was prepared by a two-step emulsification method. The optimized formulation of amphiphilic polymer gel systems is: 0.15% P(AM-NaA-DDAM), 0.3% methenamine, 0.02% resorcinol, and 0.3% citric acid. The delayed gelation time of the delayed crosslinking amphiphilic polymer gel system is closely related to the stability of the W₁/O emulsion. By using multiple emulsion delayed crosslinking method, the delayed crosslinking amphiphilic polymer gel system with diesel as the oil phase can delay the gelation time up to 168 hours.     

Equilibrium Topology and Partial Inversion of Janus Drops: A Numerical Analysis

The equilibrium topology of an aqueous Janus emulsion of two oils, O1 and O2, with water, W, [(O1+O2)/W], is numerically evaluated with the following realistic interfacial tensions (γ): γ_O2/W=5 mN m⁻¹, γ_O1/O2=1 mN m⁻¹, and γ_O1/W varies within the range 4–5 mN m⁻¹, which is the limiting range for stable Janus drop topology. The relative significance of the two independently pivotal factors for the topology is evaluated, that is, the local equilibrium at the line of contact between the three liquids and the volume fraction of the two dispersed liquids within the drop. The results reveal a dominant effect of the local equilibrium on the fraction of the O2 drop surface that is covered by O1. In contrast, for a constant volume of O2, the impact of the interfacial tension balance on the limit of the coverage is modest for an infinite volume of O1. Interestingly, when the O1 volume exceeds this value, an emulsion inversion occurs, and the O1 portion of the (O1+O2)/W topology becomes a continuous phase, generating a (W+O2)/O1 Janus configuration.     

Synthesis of europium-doped silica microspheres using the sol–gel microencapsulation method

This paper demonstrates the preparation of europium (Eu³⁺) doped silica microspheres using the W/O microencapsulation method. The water phase (W phase) solution is composed of partially hydrolyzed tetraethyl orthosilicate and acetylsalicylic acid acting as hydrophilic active agents. The Eu(NO)₃·H₂O was added into the W phase solution before mixing with the oil phase solution. Under a controlled stirring treatment, the W/O emulsion is obtained by dispersing the W phase solution in cyclohexene containing Span60 as the surfactant. 3-aminopropyl-triethoxysilane (APTES) is used as a gelling agent to encapsulate the micelles and Eu³⁺ doped silica microspheres with a mean size of around 2???m can be obtained. The experimental parameters, such as the W/O ratio, stirring condition, the amount of APTES added and the temperature, are modified and their effects on the morphology and homogeneity of the resulting Eu³⁺ doped silica microspheres are systematically studied. The Eu³⁺ ions are successfully confined inside the silica microcapsules, exhibiting an optimal red emission with a doping concentration of 3?mol%.     

Novel polymeric ionic liquid microspheres with high exchange capacity for fast extraction of plasmid DNA

A novel polymeric ionic liquid (PIL) microsphere, poly(1-vinyl-3-(2-methoxy-2-oxyl ethyl)imidazolium) hexafluorophosphate, is prepared via W/O emulsion polymerization. Rapid ion-exchange between the anionic moieties of PIL and DNA fragments is demonstrated facilitating the exchange equilibrium to be reached within 1 min. The PIL microspheres exhibit a high capacity of 190.7 μg mg⁻¹ for DNA adsorption. A fast DNA isolation protocol is thus developed with the PIL microspheres as solid phase adsorbent. It is feasible to facilitate DNA adsorption or stripping from the microspheres by simply regulating the concentration of salt. DNA adsorption is facilitated at low salt concentration, while higher concentration of salt entails DNA recovery from the microspheres. In practice, the retained DNA could be readily recovered with 1.0 mol L⁻¹ NaCl as stripping reagent, giving rise to a recovery of ca. 80.7%. The PIL microspheres are used for the adsorption/isolation of plasmid DNA from E. coli cell culture, demonstrating a superior adsorption performance with respect to that achieved by a commercial Plasmid Miniprep Kit.     

W/O、O/W型卵磷脂乳状液对CaCO3晶型的影响

Ｗ／Ｏ、Ｏ／Ｗ型卵磷脂乳状液对ＣａＣＯ３晶型的影响姚松年＊缪炜童华张操墨熊海涛（武汉大学分析测试科学系，武汉４３００７２）关键词：卵磷脂乳状液ＣａＣＯ３碳酸钙可以方解石、霰石、球霰石、胶状碳酸钙等形态存在且依次稳定性降低。珍珠是生物矿化产物，除氨基酸...     

Development of New Microencapsulation Techniques Useful for the Preparation of PLGA Microspheres

Summary: Intensive efforts were made to develop an efficient, novel microencapsulation system useful to encapsulate a model drug, risperidone, to PLGA microspheres. Methyl dichloroacetate was used as a dispersed solvent for the first time, since it possessed excellent solvency power on PLGA and readily underwent ammonolysis. A dispersed phase composed of methyl dichloroacetate, risperidone, and PLGA was emulsified in an aqueous phase to form an O/W emulsion. Adding ammonia solution into the emulsion rapidly converted methyl dichloroacetate into water‐soluble dichloroacetamide and methanol. As a result, emulsion droplets were immediately transformed into hardened microspheres. The new microencapsulation system allowed us to make PLGA microspheres with a drug payload of >40 wt.‐% and attain almost complete encapsulation efficiencies. In summary, preparing an O/W emulsion and subjecting the emulsion to ammonolysis led to development of an efficient, novel microencapsulation system. It was anticipated that the new system could make it possible to load other bioactive materials into microspheres made of various types of hydrophobic polymers.

SEM micrographs of the external and internal morphology of PLGA/risperidone microspheres.     

Determination of the electrochemical diffusion coefficient of methylene blue in SDS/n-C5H11OH/H2O system by non-probe microelectrode voltammetry

The diffusion coefficient of methylene blue (MB) is determined by the method of non-probe microelectrode voltammetry in sodium dodecyl sulfate (SDS)/n-C₅H₁₁OH/H₂O lyotropic liquid crystal system. The results obtained show that the diffusion coefficient of MB increases with water and n-pentanol contents in the microemulsions and the lyotropic liquid crystal but decreases with SDS content. The diffusion coefficient of SDS droplet in the microemulsions and the diffusion coefficient of SDS molecule in the lyotropic liquid crystal with MB all are less than those without MB. The magnitude order of the diffusion coefficient of MB is as follows: the coefficient in the oil-in-water (O/W) microemulsion is greater than the coefficient in the water-in-oil (W/O) microemulsion which is greater than the coefficient in the lamellar liquid crystal (LLC), which is also greater than the coefficient in the Hex.     

Effect of Brønsted/Lewis Acid Ratio on Conversion of Sugars to 5‐Hydroxymethylfurfural over Mesoporous Nb and Nb‐W Oxides

A series of mesoporous Nb and Nb‐W oxides were employed as highly active solid acid catalysts for the conversion of glucose to 5‐hydroxymethylfurfural (HMF ). The results of solid state ³¹P MAS NMR spectroscopy with adsorbed trimethylphosphine as probe molecule show that the addition of W in niobium oxide increases the number of Brønsted acid sites and decreases the number of Lewis acid sites. The catalytic performance for Nb‐W oxides varied with the ratio of Brønsted to Lewis acid sites and high glucose conversion was observed over Nb₅W₅ and Nb₇W₃ oxides with high ratios of Brønsted to Lewis acid sites. All Nb‐W oxides show a relatively high selectivity of HMF , whereas no HMF forms over sulfuric acid due to its pure Brønsted acidity. The results indicate fast isomerization of glucose to fructose over Lewis acid sites followed by dehydration of fructose to HMF over Brønsted acid sites. Moreover, comparing to the reaction occurred in aqueous media, the 2‐butanol/H₂O system enhances the HMF selectivity and stabilizes the activity of the catalysts which gives the highest HMF selectivity of 52% over Nb₇W₃ oxide. The 2‐butanol/H₂O catalytic system can also be employed in conversion of sucrose, achieving HMF selectivity of 46% over Nb₅W₅ oxide.     

Citric acid-loaded W1/O/W2 multiple emulsions efficiently remove colonic ammonia both in vitro and in vivo

Hepatic encephalopathy (HE) is a neuropsychiatric disorder caused by chronic and acute liver diseases. It is believed that ammonia played an important role on the pathogenesis of the disease. Herein, acid-loaded water-in-oil-in-water (W₁/O/W₂) multiple emulsions with over 95% encapsulation efficiency were prepared and used to absorb colonic ammonia. The study of citric acid release from W₁ to W₂ in bulk deionized water indicated that only 17% acid released in 8 hours, which proved the stability of the multiple emulsions and hence prevented the intestine from being irritated by acid burst release. In vitro, the W₁/O/W₂ emulsion could remove around 90% ammonia in 1.5 hours from either the 3 mmol/L ammonia solution or the artificial colonic fluid with 1 and 0.5 mmol/L ammonia without acidifying the artificial colonic fluid. In vivo, compared with lactulose, W₁/O/W₂ emulsions could efficiently reduce the blood ammonia to the similar level in the rat models with HE without increasing the water content in feces. All these results indicated a potential application of W₁/O/W₂ multiple emulsions for the treatment of HE.     

TiO2/SiO2气凝胶微球的制备及其表征

以TiOSO4和硅溶胶为原料, 加入甲酰胺作为干燥控制化学添加剂, 采用W/O乳状液中的溶胶-凝胶法制备TiO2/SiO2凝胶微球, 通过正硅酸乙酯母液浸泡、溶剂交换、陈化和常压干燥技术制备TiO2/SiO2气凝胶微球, 采用光学显微镜、SEM、TEM和BET比表面及孔分布测定等手段对所得样品进行表征. 典型的气凝胶微球样品是由粒径15 nm左右, 粒度分布相当均匀的球状纳米粒子构成的轻质纳米多孔材料, 表观密度为177 kg•m-3, 比表面积372 m2•g-1, 平均孔径22.78 nm, 孔隙率高达92.0％, 微球的宏观粒径为50 m. 依据制备条件的变化, TiO2/SiO2气凝胶微球的宏观粒径可控在10～200 m之间, 表观密度为150～300 kg•m-3, 比表面积为300～400 m2•g-1, 平均孔径在18.71～22.78 nm之间变化.     

Beiträge zur Untersuchung anorganischer nichtstöchiometrischer Verbindungen. XX. Metastabile Oxydation von Mischkristallreihen — ein Zugang zu W-reichen Blockstrukturen im System Nb2O5/WO3

Contributions to the Investigation of Inorganic Non-stoichiometric Compounds. XX. Metastable Oxidation of a Series of Solid Solutions — an Access to W-rich Block Structures in the System Nb₂O₅/WO₃ The characteristical region of existence of block structures with building elements that are limited in size in two directions ends in the system Nb₂O₅/WO₃, as was shown by previous investigations, under conditions of equilibrium at a maximum value of 2.654 O/ΣM. For the occurring phases with the ratios Nb₂O₅: WO₃ = 6:1, = 7:3, = 8:5 and = 9:8 as well we now were successful in substituting W for Nb. The original block structure and the corresponding ratio O/ΣM were preserved. The “9:8”-phase W_4/4[Nb₁₈W₇O₆₉], for example, forms solid solutions W_4/4[Nb₁₁W₁₄O₆₉] leaving the size of the building elements ([5 times; 5] blocks) unchanged. Hereby the ratio W/Nb is drastically enhanced from 0.444 to 1.364. By metastable oxidation of these solid solutions at temperatures of about 500°C, for instance in air, one comes back to the system Nb₂O₅/WO₃. In this way the region of existence of block structures could be expanded far beyond the limit at 2.654 O/ΣM to higher W/Nb values.