Microspheres of essential oil in polylactic acid and poly(methyl methacrylate) matrices and their blends

This study is focussed on micro-encapsulation of essential oils in polylactic acid (PLA) and a poly(methyl methacrylate) (PMMA) matrix as well as blends of the same. Microspheres were prepared by the solvent evaporation technique and characterised by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier transform infra-red spectroscopy (FTIR). The encapsulation efficiencies and release profiles of the essential oils were studied by gas chromatography mass spectrometry (GC-MS) and head-space solid-phase microextraction GC-MS, respectively. Furthermore, the microspheres were tested for antibacterial activity against both Gram-negative and Gram-positive bacterial strains.

The results showed that the microspheres compositions (PLA/PMMA ratio) have significant effect on their characteristics. The process adopted for preparing the microspheres promoted formation of spherical particles at the sizes of 1.5–9.5?µm. The highest encapsulation efficiency of the prepared microspheres was observed in systems consisting of linalool (81.10?±?10.0?wt. % for PLA system and 76.0?±?3.3?wt. % for PMMA system). Confirmation was also made that the release rate of the microspheres was affected by the size of the same.     

Indomethacin-Dipalmitoylphosphatidylcholine Interaction. A Calorimetric Study of Drug Release from Poly(Lactide-co-glycolide) Microspheres into Multilamellar Vesicles

A comparative study of indomethacin controlled release from poly(lactide-co-glycolide) (50:50, molecular weight 3000) (PLGA) microspheres loaded with two different amounts of drug (10.9 ± 1%, and 34.1 ± 1% w/w) and pure free indomethacin, considering the effects exerted by the drug on the thermotropic behavior of dipalmitoylphosphatidylcholine multilamellar vesicles, was carried out by differential scanning calorimetry (DSC). The release was monitored by comparing the effect exerted by the free indomethacin on lipid thermotropic behavior with that of the drug released by the microspheres and relating these effects to a lipid aqueous dispersion containing the molar ratio of drug able to cause it. By DSC measurements, the pure free indomethacin was found to be able to have a fluidifying effect on the model membrane, causing a shift toward lower values of the transitional temperature (T_m), characteristic of phospholipid liposomes, without variations in the enthalpic changes (ΔH). This shift was found to be modulated by the drug molar fraction with respect to the lipid concentration in the aqueous dispersion. Successively, calorimetric measurements were performed on suspensions of blank liposomes added to weighed amounts of unloaded and indometha-cin-loaded microspheres as well as free powdered indomethacin, and the T_m shifts of the lipid bilayer caused by the drug released from the polymeric system, as well as by the free drug, were compared with that caused by free drug increasing molar fractions dispersed directly on the membrane, employed as a calibration curve to obtain the fraction of drug released. This drug release model could be employed to determine the different kinetics involved in the drug transfer from the microspheres to a membrane. This in vitro study suggests that the kinetic process involved in drug release is influenced by the amount of drug loaded in the microspheres. This calorimetric study shows that the PLGA microspheres are a good delivery system able to sustain drug release. Moreover, the DSC technique applied to the drug interaction with biomembranes constitutes a good tool for determining the drug release representing an innovative alternative in vitro model.     

Influence of Size, Dosage, and Surface Structure on Clearance and Tissue Distribution of Intravenous Microspheres

Intravenously injected polystyrene microspheres with functional amino groups (AP-MSs, 0.2,1.0, and 4.0 urn in diameter) were cleared from the blood very rapidly. The calculated half-lives for 0.2-, 1.0-, and 4.0-μm AP-MSs were about 55,60, and 50s; no significant differences were found with 10⁶,10⁷, and 10⁸ microspheres/rat. Loading experiments showed that the liver, spleen, lung, kidney, and heart had a very high capacity to take up AP-MSs. The AP-MSs were distributed mainly to the liver, lung, and spleen, whereas other organs contained less than 1 % of injected AP-MSs. In terms of numbers of AP-MSs per gram of tissue, the highest contents were found in spleen, liver, and lung for 0.2-, 1.0-, and 4.0-um AP-MSs, respectively. There was indication of redistribution of particles from one organ to another during the first 6 h after injection. Chondroitin sulfate A (Chon) and hyaluronic acid (Hya) adsorbed or covalently linked to AP-MSs increased uptake in the liver, with Chon AP-MSs (adsorbed or linked) showing the best effect: about 25% increase compared with unadsorbed 1-μm AP-MSs. Experiments with separated cells in vitro demonstrated that 1 um AP-MSs, intravenously injected, associated only with Kupffer cells. When the microspheres were adsorbed with Chon, there was also association with liver endothelial cells. This finding indicates that conjugation of microspheres with ligands for endothelial receptors may be a useful method for directing microspheres to specific organs, even if the receptors are not by themselves phagocytic     

明胶-聚乳酸载药纳米微球的制备及其体外释药研究

采用复合乳液—溶剂挥发法制得明胶—聚乳酸载五氟脲嘧啶(5—Fu)微球，以混合型乳化剂Tween—80：Span—80＝5：1—作为初乳乳化剂，O—羧甲基壳聚糖作为复乳乳化剂，考察了明胶—聚乳酸载药微球的制备条件对微球的成球性、药物包封率及体外释药的影响。结果表明乳化剂的选择、内部水相药物浓度和PLA分子量等均对载药微球的结构与性能产生影响，经优化条件得到了成球性和体外释放都比较好的载药微球。     

Distribution of cardiac output in different models of hypertension in the conscious rat

The distribution of cardiac output was determined by 15 m radioactive microspheres in all the major organs of spontaneous, DOCA/NaCl and one kidney Goldblatt hypertensive rats and compared to normotensive Wistar rats. Although there were alterations in cardiac output distribution which were characteristic of each model of hypertension significant changes were common to all three were an increased distribution to skeletal muscle with decreases to the lungs, spleen and hepatosplanchnic tissues. The results suggest that alterations in peripheral resistance induced by hypertension are of unequal importance in the different vascular beds with certain vascular resistance changes occurring irrespective of the origin of the hypertension.Abbreviations used in this paper SHR spontaneously hypertensive rats - DOCA deoxycorticosterone acetate Supported by I.C.I. Pharmaceutical Ldt and the Mersey Regional Health Authority (Research Schemes No. 338).     

Experimentelle Bedingungen zur Reproduktion eines submucösen Steal-Phänomens am Hundemagen

Zusammenfassung Der Einfluß von Pentagastrin auf die Durchblutung des Hundemagens wurde mit 9-Mikrosphären untersucht. Schon 6 min nach dem Beginn der Pentagastrin-Infusion nimmt bei nüchternen Tieren der Fluß in allen Magenarealen zu. Mißt man die Änderung der Durchblutung zwei Stunden postprandial, so findet sich ein Durchblutungsanstieg lediglich im Bereich der Corpusmucosa, während die Antrummucosadurchblutung unter den Ausgangswert abfällt. Dieses intragastrale Steal-Phänomen findet auf der Ebene des submucösen Plexus statt.

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Experimental conditions for the reproduction of a submucous steal-phenomenon in the dog stomach

Summary The influence of pentagastrin on gastric blood flow has been investigated using 9-microspheres in dogs. As soon as 6 min after the onset of a pentagastrin infusion blood flow rises in all gastric probes in fasted animals. In dogs, fed two hours previously, such a response can only be seen in the corpus-mucosa areas. Blood flow in the antrum mucosa specimen falls beneath its initial value. This gastric steal-phenomenon takes place at the level of the submucous plexus, as has been shown earlier.

     

喷雾干燥技术在蛋白、多肽类药物微球制备中的应用

按照不同的常用载体材料（聚乳酸类和壳聚糖类），分类综述应用喷雾干燥技术制备蛋白、多肽类药物微球的研究进展，主要介绍和比较了溶液，喷雾干燥、乳剂，喷雾干燥、喷雾冷冻干燥、喷雾液中冷冻及低温喷雾提取等制备工艺的特点。     

三维腹腔镜手术联合醋酸亮丙瑞林治疗盆腔深部浸润型子宫内膜异位症疗效观察

目的 探讨三维(3D)腹腔镜手术联合促性腺激素释放激素激动剂(GnRH-a)治疗盆腔深部浸润型子宫内膜异位症(DIE)的疗效.方法 选取医院2015年7月至2018年7月收治的行3D腹腔镜手术患者110例,分为观察组和对照组,各55例.观察组予皮下注射醋酸亮丙瑞林微球治疗,对照组予孕三烯酮治疗,均持续治疗6个月.结果 ...     

5-氟尿嘧啶聚乳酸微球防治实验性增生性玻璃体视网膜病变的效果观察

目的评价5-氟尿嘧啶（5-Fu）聚乳酸微球防治增生性玻璃体视网膜病变（PVR）的效果.方法分别将5-Fu聚乳酸微球和5-Fu原料粉末注入兔眼玻璃体腔后,测定前房水中5-Fu浓度,观察5-Fu聚乳酸微球体内释放特性.将健康家兔48只随机分为3组：1组为5-Fu聚乳酸微球组;2组为无药物的聚乳酸微球对照组;3组为5-Fu原料粉末对照组.以巨噬细胞注入家兔玻璃体腔建立PVR动物模型后,1、2、3组分别向实验家兔左右两眼玻璃体中后部注入：1组注入5-Fu聚乳酸微球的BSS混悬液0.2 ml（相当于25 mg微球,含5-Fu 2.6 mg）;2组注入含有25 mg无药物聚乳酸微球的BSS混悬液0.2 ml;3组注入5-Fu注射液0.2 ml（含5-Fu 2.6 mg）.评价其防治PVR的效果.结果 5-Fu聚乳酸微球较5-Fu原料粉末消除半衰期明显延长,半衰期为379.05 h,清除率明显降低.1组中有2只眼因晶状体损伤排除试验;3组中有4只眼因发生急性药物毒性反应而排除试验.药效实验表明：21及28 d,2组视网膜脱离发生率为62.5%、71.9%;3组为64.3%、78.6%;1组为13.3%和13.3%,其中1组的视网膜脱离发生率降低,与2、3组比较,差异有统计学意义（P〈0.01）,2、3组视网膜脱离发生率的差异无统计学意义（P〉0.05）.结论 5-Fu聚乳酸微球具有明显的缓释作用,玻璃体腔植入可有效防治巨噬细胞诱发的实验性PVR.     

盐酸多西环素羧甲基壳聚糖微球的体外释放研究

目的:探讨各因素对盐酸多西环素羧甲基壳聚糖微球体外释放度的影响。方法:采用乳化-交联固化法制备盐酸多西环素羧甲基壳聚糖微球(doxycycline hydrochloride-carboxymethyl chitosan-microspheres,DXY-CMCTS-MS),采用动态透析法测定体外释药性能,用紫外分光法测定盐酸多西环素浓度,绘制其释放曲线。结果:释放介质pH越大,交联剂量越大,固化时间越长,药物/载体比例越小,药物的释放则越慢。结论:该制剂制备工艺切实可行,所得DXY-CMCTS-MS具有明显的缓释效果。