膜吸收用疏水性多孔膜结构参数的确定

理论分析了疏水性多孔膜气体渗透原理和膜各种结构特征参数的关系,并建立了计算气体渗透通量的模型方程,以及确定多孔膜曲折因子等结构参数的方法．通过气体渗透实验和建立的模型,对6种聚四氟乙烯(PTFE)多孔平板膜的曲折因子等结构参数进行了测试计算,并根据测得的膜孔隙率结果,比较了曲折因子与孔隙率的关系．对不同气体透过不同结构参数的多孔膜的传递形式进行了讨论．     

Microstructural and Interfacial Designs of Oxygen‐Permeable Membranes for Oxygen Separation and Reaction–Separation Coupling

Mixed ionic–electronic conducting oxygen‐permeable membranes can rapidly separate oxygen from air with 100% selectivity and low energy consumption. Combining reaction and separation in an oxygen‐permeable membrane reactor significantly simplifies the technological scheme and reduces the process energy consumption. Recently, materials design and mechanism investigations have provided insight into the microstructural and interfacial effects. The microstructures of the membrane surfaces and bulk are closely related to the interfacial oxygen exchange kinetics and bulk diffusion kinetics. Therefore, the permeability and stability of oxygen‐permeable membranes with a single‐phase structure and a dual‐phase structure can be adjusted through their microstructural and interfacial designs. Here, recent advances in the development of oxygen permeation models that provide a deep understanding of the microstructural and interfacial effects, and strategies to simultaneously improve the permeability and stability through microstructural and interfacial design are discussed in detail. Then, based on the developed high‐performance membranes, highly effective membrane reactors for process intensification and new technology developments are highlighted. The new membrane reactors will trigger innovations in natural gas conversion, ammonia synthesis, and hydrogen‐related clean energy technologies. Future opportunities and challenges in the development of oxygen‐permeable membranes for oxygen separation and reaction–separation coupling are also explored.     

Critical evaluation of permeation enhancers for oral mucosal drug delivery

Background: Drug delivery via oral mucosa is an alternative method of systemic administration for various classes of therapeutic agents. Among the oral mucosae, buccal and sublingual mucosae are the primary focus for drug delivery. Buccal delivery offers a clear advantage over the peroral route by avoidance of intestinal and hepatic first-pass metabolism. However, despite offering the possibility of improved systemic drug delivery, buccal administration has been utilized for relatively few pharmaceutical products so far. One of the major limitations associated with buccal delivery is low permeation of therapeutic agents across the mucosa. Various substances have been explored as permeation enhancers to increase the flux/absorption of drugs through the mucosa, but irritation, membrane damage, and toxicity are always associated with them and limit their use. A clinically accepted permeation enhancer must increase membrane permeability without causing toxicity and permanent membrane damage. To date, the information available on oral mucosal permeation enhancement is much less than transdermal enhancement, though oral mucosa is more resistant to damage than other mucosal membranes. This article reviews the various categories of permeation enhancers for oral mucosal drug delivery, their mechanism of action, their usefulness, and the limitations associated with their use. Conclusion: To optimize the concentration of enhancer to limit its toxicity while facilitating an enhancing effect reproducibly will be a big challenge for future developments. Advances in permeability modulation and formulation with appropriate enhancers can provide for effective and feasible buccal drug delivery for many drugs, which otherwise have to be injected or ingested with water.     

Temperature-dependent gas transport and its correlation with kinetic diameter in polymer nanocomposite membrane

Activation energies for permeation of polymer nanocomposite membrane have not been reported so far. A trade-off relation between permeability and selectivity shows that as permeability increases, the selectivity decreases. Attempts have been made to see this trade-off relation at relatively higher temperature. It is found that selectivity decreases drastically with increasing temperature. A polymer–matrix composite was prepared by adding silica nanoparticles using casting method. Pure gas permeability was measured using a constant volume–variable pressure method at different temperature ranges from 35 to \(70^{\circ }\hbox {C}\). The Van’t Hoff relation was used to estimate the activation energy for permeation. It is found to decrease as compared with virgin polycarbonate and it increases with kinetic diameter. For the first time, the permeability and selectivity for nanocomposite membrane are reported as a function of temperature. Activation energies for different gases have been calculated for nanocomposite membrane and compared with that of virgin polymer membrane. Decrease in activation energies for permeation (\(E_\mathrm{p}\)) with increasing kinetic diameter has been observed for both the membranes. Selectivity reduces with temperature for both the membranes. Mechanical and thermal properties of nanocomposite membrane have been investigated using a dynamic mechanical analyser and differential scanning calorimetry, respectively. Scanning electron microscopy has been used to study surface morphology. The results show modification in physical properties due to incorporation of silica nanoparticles.     

聚乙二醇丙烯酸酯表面改性聚醚砜酮微孔膜的结构和性能

为了提高聚醚砜酮(PPESK)微孔膜的亲水性和抗污性,采用紫外(UV)辐照引发聚乙二醇丙烯酸酯(PEGA)在膜上发生接枝和交联,在膜表面形成稳定的亲水层.利用场发射扫描电镜(SEM)研究了固定PEGA后PPESK膜表面形貌的变化.表面改性后PPESK膜的水接触角的降低表明PEGA的固定有利于提高其亲水性,蛋白质静态吸附实验显示膜的抗蛋白质污染能力增强,渗透实验表明膜表面较低数量的PEGA亲水链有利于提高PPESK微孔膜的水通量,膜的溶质截留率增大,截留分子量(MWCO)减小.     

HPLC determination of tetracycline antibiotics in milk with post-column derivatization and fluorescence detection

The conditions for sensitive and selective determination of tetracyclines in milk in the form of their complexes with Mg²⁺ via the HPLC method with post-column derivatization and fluorescence detection are found. It is shown that the fluorescence of tetracycline-Mg²⁺ complexes in microemulsions is 1.8 times more intense than that in aqueous acetonitrile medium. The detection limits of tetracycline, oxytetracycline, and doxycycline are 5, 8 and 25 ng mL^–1, respectively.     

Kinetics and Thermodynamics of Drug Permeation Through Silicone Elastomers (I) Effect of Penetrant Hydrophilicity

The hydrophilicity of progesterone, a lipophilic penetrant, was progres sively increased by addition of one or more hydroxy substituents at different positions on the steroid skeleton. Effects of these hydrophilic substituents on the kinetics and thermodynamics of permeation of progesterone molecules through polydimethylsiloxane and polytrifluoropropylmethylsiloxane membranes were studied. The addition of OH groups was found to reduce substantially the apparent and intrinsic permeation rates of progesterone. The magnitude of this reduction was observed to be dependent upon the number and the position of hydroxy groups and could be attributed to the decrease in the polymer solubility and the increase in the aqueous solubility of progesterone molecules. A remarkable difference was observed between the intrinsic and apparent rates of permeation for progesterone, while no significant difference for the hydroxyl derivatives of progesterone. The rate of permeation increased with temperature as expected from the Arrhenius relationship. The energy required for membrane permeation was noted to be relatively constant and independent of hydroxylation. After normalization, the membrane permeability of progesterone derivatives was found to be higher in polydi methylsiloxane than in polytrifluoropropylmethylsiloxane, which can be attributed to the substitution of methyl group in the polydimethylsiloxane backbone by a more polar and bulkier trifluoropropyl substituent. The substituent effect of trifluoropropyl group is substantial for progesterone but less significant for hydroxy derivatives.     

Evaluation of silicone-based pressure-sensitive adhesives for transdermal drug delivery [II] effect of penetrant lipophilicitv

Abstract

An adhesive polymer drug dispersion-type transdermal drug delivery (a-TDD) system, consisting of a single drug-loaded adhesive polymer layer sandwitched between a drug-impermeable backing membrane and a detachable release liner, was developed from two silicone-based pressure-sensitive adhesive polymers for the controlled administration of drugs. The effect of variation in penetrant lipophilicity, using a series of testosterone derivatives with an increasing number of methyl groups in the steroid skeleton, on the release kinetics from the a-TDD system and skin permeation rate profiles was investigated. Absence of a methyl group at the 19th position of testosterone increased the flexibility of the steroid molecule and thus yeilded higher diffusivity and greater skin permeation rate. Addition of esters at the 17 ß-position resulted in a reduction in diffusivity with an increase in the alkyl chain length of the ester. These esters were found to be bioconverted to testosterone during permeation through the intact hairless rat skin.     

钯膜制备及渗氢性能研究

随着膜分离技术的不断发展,渗氢用钯基膜由于具有优异的透氢速率、透氢选择性及良好的化学和热稳定性,已被广泛应用于氢提纯分离领域。介绍了钯透氢膜的种类、透氢机理和制备方法,总结了钯膜从最初的纯钯膜、钯合金膜到钯复合膜的发展历程和氢渗透性能研究,并重点介绍了以铌钯复合膜为代表的新型Pd/bcc型复合膜氢渗透性能的研究进展。     

Ibuprofen Release from Beads Coated with an Experimental Latex: Effect of Certain Variables

The objective of this study was to evaluate the effect of factors such as drug loading, particle size, plasticizer type, antiadherent type, and annealing method on the release of ibuprofen from controlled-release beads coated with an experimental latex. Further, the in vitro release kinetics and mechanism of drug transport across the polymeric membrane have been investigated. Ibuprofen-loaded beads were coated with the experimental latex using a fluidized-bed coating machine (Uniglatt). The drug release from these spherical membrane reservoir systems appeared to be diffusion controlled. Evaluation of the effect of osmotic pressure by using dissolution media of various osmolal concentrations indicated that it has no significant effect on the drug release. To further elucidate the mechanism of release from these polymeric membranes, the permeation of drug through free films was studied.     

Kinetics and Thermodynamics of Drug Permeation Through Silicone Elastomers (II) Effect of Penetrant Lipophilicity

The permeation of testosterone analogs through silicone membranes was studied. The variation in the lipophilicity of testosterone molecules was accomplished by the addition or elimination of methyl group and the formation of ester. Furthermore, the effects of replacing one of the CH₃ groups on the dimethylsiloxane unit in the silicone polymer chains by a polar CH₂CH₂CF₃, group, which changes polymer characteristics and thus affects the membrane permeability, was investigated as well. It was found that potential which might prevent flocculation altogether. This can lead to caking. The lowest concentration effective in prevent ing coagulum formation should be used.

Suspensions made from a fluid aluminum hydroxide concentration were easy to redisperse after six weeks of storage. The sedimentation volume was 0.64. Addition of 0.2% xanthan gum raised the sedimentation volume to a value of 1.0. There was no evidence of coagulum formation in this system.     

担载型中空纤维混合导体氧渗透膜的制备与性能研究

采用干湿法纺丝技术制备Sr_0.7Ba_0.3Fe_0.9Mo_0.1O_3-δ(SBFM)中空纤维支撑体, 以Nb₂O₅掺杂的SrCo_0.8Fe_0.2O_3-δ (SCFNb)为膜材料, 采用旋转喷涂结合共烧结技术制备出担载型SCFNb/SBFM中空纤维氧渗透膜。借助于XRD、SEM、热膨胀分析、透氧及膜反应性能测试等手段, 分别对样品的晶相结构、膜微观结构、支撑体与膜层的烧结行为、膜的氧渗透通量及膜反应性能进行了研究。结果表明, 膜层与支撑体的晶相结构仍保持钙钛矿主体相。支撑体具有单一海绵孔/指状孔结构, 膜厚为5 μm且致密无缺陷, 膜层与支撑体结合良好。在900℃时, 氧渗透通量达到0.74 mL/(cm²·min)。850℃下甲烷部分氧化膜反应稳定操作超过200 h, 稳态下氧渗透通量为4.5 mL/(cm²·min)。研究表明, 担载型SCFNb/SBFM中空纤维氧渗透膜具有较高的氧渗透通量, 同时具有良好的膜反应稳定性。     

Novel application of Eudragit RL and cholesteryl oleyl carbonate to thermo-sensitive drug delivery system

The Eudragit RL 100 and propylene glycol (PG) membranes with and without cholesteryl oleyl carbonate (COC) were prepared by the solvent casting method to pioneer a novel application of a thermo-sensitive drug delivery system. After that, the properties of these membranes were investigated by thermal, scanning, and porosity studies. Drug permeation studies through all membranes were carried out using salbuthamol sulphate (SBS) at constant temperatures (25°C and 37°C), respectively. The permeability of SBS through the membranes with COC has been shown to be a discontinuous function of temperature, that is, their permeability increased steeply above the phase transition temperature (37°C) of the COC. The thermo-sensitive permeation mechanism for the membranes might be based on the structure change of the membranes caused by the phase transition, so that the membranes could absorb more water. Considering the high biological safety of Eudragit RL 100 and PG membranes with and without COC might be used to develop a novel thermo-sensitive drug delivery system.     

Permeation of solvents through disk type rice husk silica membrane modified with alkyl silylation reagents

Rice husk silica (RHS) which was obtained with thermal treatment of rice husk has the size of approximately 10 micrometer with 4-5 nm pore. RHS can be mold to a disk type membrane. The membrane may have submicron pore originated from the space among the particles, and the nano pores of the rice husk silica (RHS pore). Even it is difficult to adjust the size of the pores, we can suggest that the membrane shows different permeability for the organic/inorganic solvents if the affinity between the surface of the pores and the permeating molecule is changed. In this study, we investigated the permeation of the typical solvents such as water, ethanol and toluene to the RHS membranes sintered at 1100 degrees C, 1150 degrees C and 1200 degrees C and modified with triethoxymethyl silane (CH3)Si(C2H5O)3, diethoxydiemethyl silane (CH3)2Si(C2H5O)2 and ethoxytriemethyl silane (CH3)3Si (C2H5O). The result showed that permeability of original membranes for water (e.g., 1100 degrees C, 2.87 x 10(-3) mol/m2 s Pa) was larger than ethanol (1100 degrees C, 5.51 x 10(-4) mol/m2 s Pa) and toluene (1100 degrees C, 3.09 x 10(-4) mol/m2 s Pa) at the sintering temperatures. For the silane modified membranes, the permeability for water decreased drastically while those for ethanol and toluene increased.     

丝素-壳聚糖共混膜的制备及其金属离子渗透行为的研究

采用壳聚糖(CS)对天然高分子丝素(SB)进行改性,制备了丝素-壳聚糖(SB-CS)共混膜.FTIR、TGA、SEM的分析表明,该共混膜中SB和CS具有良好的相容性,壳聚糖改善了丝素膜的吸水性和机械性能.通过渗透实验发现不同的金属离子在共混膜中的渗透速率有很大的差异,一些常见的金属离子渗透速率的大小顺序为:K+>Ca2+>Cd2+>Pb2+>Cu2+>Ni2+.     

磺化聚酰亚胺/SiO2复合膜的制备及其质子交换性能研究

制备了具有不同硅含量的磺化聚酰亚胺/二氧化硅(SPI/SiO2)复合膜,研究了SiO2的引入对复合膜的力学性能、耐热性能、尺寸稳定性以及抗氧化和耐水解稳定性的影响规律,并对其质子传导率和甲醇渗透率进行了评价。结果表明,与商业化的Nafion115膜相比,复合膜表现出更优异的阻醇特性和选择透过性,其中SPI/SiO2-2复合膜具有更突出的高温质子传导特性。     

甲基硅橡胶膜的透气特性

甲基硅橡胶是气体透过量较大的一种，曾和于呼吸困难患者使用的医和富氧器或以节能为目的的燃烧系统，我们研究了甲基硅橡胶均质膜在不同温度下的透气性能，用压力法测定了它们的渗透系数、溶解度系数和扩散系数，比较和讨论了它们的透过机理。     

Determination of persistent tetracycline residues in soil fertilized with liquid manure by high-performance liquid chromatography with electrospray ionization tandem mass spectrometry

Little is known about the occurrence and the fate of veterinary drugs in the environment. Therefore, a liquid chromatography/tandem mass spectrometry method was developed and employed to investigate in detail the distribution and persistence of the frequently used tetracyclines and tylosin in a field fertilized with liquid manure on April 2000 and April 2001; soil sampling was performed in May 2000, November 2000, and May 2001. We detected 4.0 mg/kg tetracycline and 0.1 mg/kg chlortetracycline in the liquid manure of April 2000, as well as comparable amounts in the liquid manure of April 2001. In the soil samples of May 2001, the highest average concentrations of 86.2 (0-10 cm), 198.7 (10-20 cm), and 171.7 microg/kg (20-30 cm) tetracycline and 4.6-7.3 micro/kg chlortetracycline (all three sublayers) were found. At soil depths between 30 and 90 cm, as well as in soil or groundwater, tetracyclines could not be detected. In addition, oxytetracycline and tylosin could not be detected in any sample investigated. We conclude that tetracyclines enter the environment in significant concentrations via repeated fertilizations with liquid manure, build up persistent residues, and accumulate in soil. Therefore, tetracyclines may have a potential risk and investigations on the environmental effects of these antibiotics are necessary.     

氧化石墨烯/聚氨酯杂化膜的原位聚合构建及气体渗透性

采用Hummers法制备了3种不同氧化程度的氧化石墨烯(GO),通过聚氨酯(PU)单体(4,4’-二异氰酸苯酯(MDI)和1,4-丁二醇(BDO))与GO的原位聚合构建了GO/PU杂化膜。利用XRD、Raman、FTIR和TEM等表征了GO的结构;探讨了GO填充量对GO/PU杂化膜的形貌和CO2、N2渗透性的影响。结果表明:3种不同氧化程度的GO均呈完全剥离状态,为半透明片状结构;随着氧化程度的增加,拉曼D峰与G峰的相对强度比分别为0.947、1.103和1.245;GO的氧化程度对GO在溶剂和杂化膜中的分散性有较大影响,氧化程度越高,分散性越好。GO/PU杂化膜的CO2、N2渗透系数及CO2/N2渗透选择因子均随GO填充量的增加先增大后减小;当中等氧化程度的GO(M-GO)与(MDI+BDO)的质量比为1.0%时,M-GO/PU杂化膜的CO2渗透系数为63.6×10-13 cm3(STP)/(cm·Pa·s),其中STP表示标准温度及压力,CO2/N2渗透选择因子可达48.5;填充适量的GO能显著提高GO/PU杂化膜的CO2渗透性及CO2/N2渗透选择性。     

Rational Delivery Strategies for the Design of Peptides with Enhanced Oral Delivery

One of the most significant biological barriers to delivery of peptides and peptide mimetics is the intestinal mucosa, which is a cell monolayer with tight intercellular junctions representing both an anatomical and an enzymatic barrier to the permeability of most polar molecules. In order to properly evaluate strategies for enhancing membrane permeability of peptides and peptide mimetics, our laboratory has developed an in vitro model of the intestinal mucosa, which consists of human adenocarcinoma cells (Caco-2) grown onto microporous membranes. This cell culture system, as well as an in situ intestinal perfusion model, has been employed in our laboratory to evaluate strategies for enhancing membrane permeability of peptides. The strategies that will be discussed in this article include: (1) designing conjugates of peptide mimetics targeted to endogenous transporter systems (e.g., bile acid) so as to enhance their intestinal permeability by a carrier-mediated pathway; and (2) optimizing the lipophilicity, hydrogen-bonding potential and conformation of peptide mimetics so as to enhance their intestinal permeability by passive diffusion.