聚乙二醇3350分子量与分布测定研究

目的：建立药用辅料聚乙二醇3350分子量与分布测定方法,并对3个厂家9批样品进行比较研究。方法： 采用Waters凝胶渗透色谱（GPC）处理系统、示差折光检测器进行分子量及分布测定,采用TA 差示扫描量热仪（DSC） q2000系统对样品的热效应进行研究 。结果：该方法以分子量400～5 800范围内的聚乙二醇对照品建立三阶校正曲线,回归系数0.999 9,各校正点平均偏差均小于2%,能够准确测定聚乙二醇3350的重均分子量、分布系数等信息;DSC测定图谱能够反映样品的纯度,进一步确认相关质量。结论：高效凝胶渗透色谱方法是测定聚乙二醇相关辅料分子量及分布的可靠方法,用于确定重均分子量、分布系数等多分散化合物关键质量参数具有操作简单、结果准确的特点,配合差示扫描量热法能够分辨更多的质量属性,可用于产品质量均一性监控和辅料对比筛选研究。     

The effect of the molecular weight of polyethylene glycol on the bioavailability of paracetamol-polyethylene glycol solid dispersions

A controlled study of the bioavailability of paracetamol in solid dispersion with PEG 6000, 10000 and 20000 has been made. The total amount of paracetamol excreted in urine increased with molecular weight of the PEG, but the rate of absorption of the drug was unaffected.     

Photoinactivation of vesicular stomatitis virus with fullerene conjugated with methoxy polyethylene glycol amine.

Fullerene is known to effectively produce mainly singlet oxygen by absorbing light energy, and therefore may be useful as a virucidal photosensitizer. This study was designed to investigate the virucidal activity of a water-soluble fullerene derivative, which is conjugated with methoxy polyethylene glycol amine to enhance its water solubility. Vesicular stomatitis virus (VSV) was inactivated upon illumination with this water-soluble fullerene, in a concentration- or dose-dependent manner. The titer of VSV was reduced by >5log 10 in the presence of 10 mg/ml (400 microM) fullerene derivative with 120 J/cm2 white light irradiation. VSV inactivation was inhibited by oxygen removal or by the addition of sodium azide, a known singlet oxygen scavenger. The substitution of H2O by D2O, which is known to prolong the lifetime of singlet oxygen, promoted the virucidal activity. These results indicate that singlet oxygen may play a major role in VSV photoinactivation by the water-soluble fullerene derivative. The concentration needed for virus inactivation is higher than that of other sensitizers such as methylene blue.     

布洛芬葡萄糖醛酸结合物的立体选择性胆排泄及其机制研究

目的：为阐明药物转运体在布洛芬（IB）葡萄糖醛酸结合物（IBG）胆排泄中的作用,对IB和IBG在先天性高胆红素血症大鼠（EHBR）和正常SD大鼠（SDR）的胆排泄和血药浓度差异进行了研究。方法：按20 mg/kg剂量静脉注射IB消旋体后,以HPLC法测定了血和胆汁中IB与IBG的浓度。结果：结果表明IBG的胆排泄在EHBR受到了明显抑制,其S-型和R-型IBG的6小时胆排泄量分别为给药量的1.7 %±1.0 %和0.6 %±0.9 %,而在SDR,该值分别为18.4 %±4.0 %和3.0 %±2.4 %。这些结果同时显示了S-型IBG在两种大鼠的胆排泄量均较R-型IBG大,说明该过程存在明显的立体选择性。由于IBG在EHBR的胆排泄受到抑制,其血中的浓度较高。结论：EHBR是一种先天性多药耐药相关蛋白（Mrp2）缺失的大鼠,可以推测布洛芬葡萄糖醛酸结合物的胆排泄过程主要是由Mrp2介导。但由于IBG在EHBR仍有少量胆排泄,故不排除其它转运体参与该过程的可能性。     

Effects of polyethylene glycol molecular weight and concentration on lactate dehydrogenase activity in solution and after freeze-thawing

Lactate dehydrogenase (LDH) is a tetrameric enzyme that has been used as a model for labile protein drugs. Polyethylene glycols (PEGs) have been proposed as excipients to stabilize labile proteins in solution and during the freezing portion of the lyophilization cycle. The aim of this study was to determine the effects of PEG molecular weight and concentration on the activity of LDH. In general, PEG protection increases with PEG molecular weight and concentration. PEGs slow the loss of activity in LDH solutions stored at 4 degrees C, but are not sufficiently effective to allow for a solution product. PEGs 8000, 10,000, and 20,000 show full freezing protection at less than 0.01%, while lower molecular weight PEGs need higher concentrations to produce protection upon freezing. Circular dichroism (CD) studies of LDH solutions before and after freezing with PEG 400 and PEG 8000 confirm the activity studies. The CD spectrum of LDH before freezing shows the classic alpha helix pattern. After unprotected LDH solution is frozen and thawed, the CD spectrum erodes. Low concentrations of PEG 8000 (1% or less) preserve the alpha helix profile after freezing of the samples. PEG 400 preserves the alpha helix CD profile in a stepwise fashion with increasing concentrations. The CD and activity data suggest that PEGs can protect alpha helix structures and activity of LDH through the freezing process.     

Studies on the biliary excretion mechanism of drugs. I. Biliary excretion of azo dyes in the rat

The mechanism of biliary excretion of the azo dyes, Azorubin S (AS), Amaranth (AM) and New Coccine (NC), in rats was investigated. It was observed that these azo dyes have an apparent transport maximum (Tm) for their biliary excretion. Further, the biliary excretion of these dyes was markedly depressed by phenolphthalein glucuronide (PPG) and probenecid, which are considered to be actively excreted into bile. The results, therefore, suggest that the biliary excretion of these dyes in rats involves an active transport process.     

Biodistribution, metabolism, and in vivo gene expression of low molecular weight glycopeptide polyethylene glycol peptide DNA co-condensates

The biodistribution, metabolism, cellular targeting, and gene expression of a nonviral peptide DNA gene delivery system was examined. (125)I-labeled plasmid DNA was condensed with low molecular weight peptide conjugates and dosed i.v. in mice to determine the influence of peptide DNA formulation parameters on specific gene targeting to hepatocytes. Optimal targeting to hepatocytes required the combined use of a triantennary glycopeptide (Tri-CWK(18)) and a polyethylene glycol-peptide (PEG-CWK(18)) to mediate specific recognition by the asialoglycoprotein receptor and to reduce nonspecific uptake by Kupffer cells. Tri-CWK(18)/PEG-CWK(18) DNA co-condensates were stabilized and protected from metabolism by glutaraldehyde crosslinking. An optimized formulation targeted 60% of the dose to the liver with 80% of the liver targeted DNA localized to hepatocytes. Glutaraldehyde crosslinking of DNA condensates reduced the liver elimination rate from a t((1/2)) of 0.8 to 3.6 h. An optimized gene delivery formulation produced detectable levels of human alpha1-antitrypsin in mouse serum which peaked at day 7 compared to no expression using control formulations. The results demonstrate the application of formulation optimization to improve the targeting selectivity and gene expression of a peptide DNA delivery system.     

Evidence of a specialized transport mechanism for the intestinal absorption of baclofen

Absorption of the spasmolytic drug baclofen in three selected intestinal segments of living anaesthetized rats in situ, is shown to be a specialized transport mechanism obeying Michaelis-Menten kinetics. Equation parameters were calculated through different procedures, whose features are discussed. A computer method based on the integrated form of Michaelis-Menten equation which reproduces the entire time course of drug absorption from the data found in three intestinal perfusion series at different initial concentrations, yielded Vm and Km values of 12.0 mg h-1 and 8.0 mg, respectively, in the mean segment of the small intestine, a rather selective absorption site for baclofen. Lesser but comparable absorption rates were found in the proximal and distal segments of the small intestine, whereas in colon, drug absorption was negligible. Baclofen transport was significantly reduced in the presence of the enzymatic inhibitor sodium azide. If these results were extrapolated to humans, they would explain the excellent bioavailability profiles reported for baclofen at normal doses in spite of its physicochemical properties, which do not favour passive diffusion. Based on the same principle, the administration of usual doses at shorter time intervals could be recommended, instead of high, when higher plasma levels at steady-state are needed. On the other hand, more than 8-h sustained-release preparations of baclofen should, probably, be avoided.     

Statistical analysis of the effects of polyethylene glycol concentration and molecular weight on the sedimentation and resuspendability behavior of model aqueous dispersions

This work investigates the flocculation effect of polyethylene glycol (PEG) on typical aqueous dispersions, such as O/W emulsions and solid/liquid suspensions. Hereby, sunflower oil and flubendazole were selected as model ingredients, whereas microfluidization at variable driving air pressure was used to enable particle size distribution variations for both systems. The molecular weight of PEG varied from 2000 to 12,000 g/mol while its concentration ranged from 50 to 100 mg/ml. Statistical analysis revealed that both PEG concentration and molecular weight showed a flocculation enhancing effect. Hereby the inhibiting effect of particle size toward the formation of voluminous and easily resuspendable sediment could at least partially be overcome by selecting appropriate PEG characteristics.     

Impact of molecular weight on the mechanism of cellular uptake of polyethylene glycols (PEGs) with particular reference to P-glycoprotein

Polyethylene glycols (PEGs) in general use are polydisperse molecules with molecular weight (MW) distributed around an average value applied in their designation e.g., PEG 4000. Previous research has shown that PEGs can act as P-glycoprotein (P-gp) inhibitors with the potential to affect the absorption and efflux of concomitantly administered drugs. However, questions related to the mechanism of cellular uptake of PEGs and the exact role played by P-gp has not been addressed. In this study, we examined the mechanism of uptake of PEGs by MDCK-mock cells, in particular, the effect of MW and interaction with P-gp by MDCK-hMDR1 and A549 cells. The results show that: (a) the uptake of PEGs by MDCK-hMDR1 cells is enhanced by P-gp inhibitors; (b) PEGs stimulate P-gp ATPase activity but to a much lesser extent than verapamil; and (c) uptake of PEGs of low MW (<2000 Da) occurs by passive diffusion whereas uptake of PEGs of high MW (>5000 Da) occurs by a combination of passive diffusion and caveolae-mediated endocytosis. These findings suggest that PEGs can engage in P-gp-based drug interactions which we believe should be taken into account when using PEGs as excipients and in PEGylated drugs and drug delivery systems.     

Control of molecular weight cut-off for immunoisolation by multilayering glycol chitosan-alginate polyion complex on alginate-based microcapsules

Glycol chitosan is a positively charged polysaccharide which is water-soluble at pH 7.4, and is able to form a polyion complex (PIC) with anionic polymers, such as alginate. The authors attempt to develop a novel type of alginate-based microcapsule using this glycol chitosan for a islets-encapsulated bioartificial pancreas. The number of layers composed of glycol chitosan-alginate (GC-Alg) PIC were optimized, in order to cut off immunoglobulin transport and to protect encapsulated islets from the host immune reaction, and the transport characteristics were evaluated of glucose, bovine serum albumin (BSA) and gamma-globulin. To add mechanical stability to the microcapsule, calcium ions, which crosslinked the alginate polymers close to the interface between core Ca-alginate and multilayered membrane, were partially substituted with barium ions after the formation of multilayered Ca-alginate gel beads. The partition coefficients of BSA and gamma-globulin were decreased with the increasing number of layers. The immunoisolation was achieved against gamma-globulin with four layers of the GC-Alg PIC membrane, while BSA could permeate the membrane. The four-layered Ba-alginate gel bead had a good permeability for glucose, giving a diffusion coefficient corresponding to 80% of that in pure water. Insulin secretion from the islets in the four-layered Ba-alginate microcapsule was satisfactorily observed with the fractional stimulation ratio of 2.17. This result indicates that the encapsulated islets maintained their viability even after encapsulation. It was, thus, shown that the Ba-alginate microcapsule with four layers of the GC-Alg PIC membrane is promising as the microencapsulation material for a bioartificial pancreas.     

Control of molecular weight cut-off for immunoisolation by multilayering glycol chitosan-alginate polyion complex on alginate-based microcapsules

Glycol chitosan is a positively charged polysaccharide which is water-soluble at pH 7.4, and is able to form a polyion complex (PIC) with anionic polymers, such as alginate. The authors attempt to develop a novel type of alginate-based microcapsule using this glycol chitosan for a islets-encapsulated bioartificial pancreas. The number of layers composed of glycol chitosan-alginate (GC-Alg) PIC were optimized, in order to cut off immunoglobulin transport and to protect encapsulated islets from the host immune reaction, and the transport characteristics were evaluated of glucose, bovine serum albumin (BSA) and gammaglobulin. To add mechanical stability to the microcapsule, calcium ions, which crosslinked the alginate polymers close to the interface between core Caalginate and multilayered membrane, were partially substituted with barium ions after the formation of multilayered Ca-alginate gel beads. The partition coefficients of BSA and gamma-globulin were decreased with the increasing number of layers. The immunoisolation was achieved againstgamma-globulin with four layers of the GC-Alg PIC membrane, while BSA could permate the membrane. The four-layered Ba-alginate gel bead had a good permeability for glucose, giving a diffusion coefficient corresponding to 80% of that in pure water. Insulin secretion from the islets in the four-layered Ba-alginate microcapsule was satisfactorily observed with the fractional stimulation ratio of 2.17. This result indicates that the encapsulated islets maintained their viability even after encapsulation. It was, thus, shown that the Ba-alginate microcapsule with four layers of the GC-Alg PIC membrane is promising as the microencapsulation material for a bioartificial pancreas.     

Formulation of polyethylene glycol ointment bases suitable for tropical and subtropical climates. I

The present study dealt with the investigation of the physical characteristics of 18 polyethylene glycol ointment bases with the aim of finding out their suitability for use in tropical and subtropical climates. Different ratios of low and high molecular weight polyethylene glycols were helpful for preparation of these ointment bases. The investigated physical characteristics included the drop point, the congealing range and the spreadability properties of bases. The drop point was determined by the Ubbelohde apparatus, the congealing range by the double-walled Zhuckov flask, penetrability by penetrometer, and spreadability by the parallel plate extensometer. The results of these physical parameters indicated that PEG 400:PEG 4000 blend gave very good bases for use in tropical and subtropical areas. Furthermore, it was observed that, the type and the amount of PEG used would affect greatly the drop point, congealing range and consistency of the prepared bases. Results obtained with PEG 2000 and PEG 6000 bases showed less variability with respect to molecular weight and solid content.     

Pegloticase, a polyethylene glycol conjugate of uricase for the potential intravenous treatment of gout

Savient Pharmaceuticals Inc (formerly Bio-Technology General Corp), under license from Duke University, is developing pegloticase, PEG conjugates of uricase (urate oxidase), for the potential treatment of gout. The in-life portion of the phase III trials have been completed.