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.     

Formation of Regular Hole Pattern in Polymer Films

Ordered macroporous materials recently have attracted much attention. A method that utilizes the condensation of monodisperse water droplets on a polymer solution is proposed for the preparation of honeycomb microporous films. Our results show that it is a general method that can be used for patterning a wide range of polymers. The presence of water vapor and polymer is necessary for the formation of regular holes in films. The formation of hexagonal packing instead of other kinds of packing takes place because the hexagonal packing has the lowest free energy. The formation mechanisms of regular hole pattern and imperfections in the hexagonal packing are proposed.

Hexagonal hole structures in a PMMA film.     

生物降解型尼索地平微球的研究

目的制备尼索地平的PLGA微球,并研究其体内外释药行为.方法采用溶剂挥发法制备微球,电镜下观察微球形态,HPLC法测定微球的载药量、包封率及累积释药量.采用HPLC法测定家兔体内的血药浓度.结果微球形态圆整,表面光滑.微球的粒径为15.3±3.8μm,载药量为21.16%,包封率为85.40%.微球的体外释药行为的拟合方程为1-Q=0.7654(1-t/t     

尼索地平微球的制备

采用溶剂挥发法制备了尼索地平微球 ,考察了制备工艺中影响微球质量的 5个主要因素 ,筛选出较理想的处方和工艺。所得微球形态圆整 ,表面光滑 ,粒径 (18.2± 3.8) μm,载药量 2 1.2 % ,包封率 85 .4 %。     

甲氨碟呤脂质体的几种制备方法比较

目的探讨脂质体的制备方法 ,以便在具体工作中根据不同的目的选择适当的制备方法。方法采用逆相蒸发法、注射法、薄膜法和超声法制备包裹了甲氨喋呤和环胞苷的脂质体。对各种方法的关键步骤进行了讨论。结果被包物质如不稳定 ,采用薄膜法轻轻振摇超过 10h ,包封率可比短时间或震荡激烈提高。被包物质如经过短时间的超声和有机溶剂处理 ,采用逆相蒸发法 ,可获得较高包封率。结论根据被包物质的性质及具体工作不同 ,选择适当的脂质体制备方法 ,会得到较高的包封率和工作效率     

黄芩苷脂质体的制备工艺研究

目的:探讨黄芩苷脂质体的制备工艺.方法:采用逆相蒸发法、乙醚注入法和薄膜超声法制备黄芩苷脂质体,SephadexG-50凝胶柱分离脂质体,UV-法测定包封率,Zetasizer3000粒度测定仪测定其粒径,透射电子显微镜进行形态学观察.结果:逆相蒸发法制备的黄芩苷脂质体平均粒径360nm,包封率56.02%;乙醇注入法平均粒径2600nm,包封率26.14%;薄膜-超声法平均粒径1200nm,包封率53.65%.结论:逆相蒸发法制备的黄芩苷脂质体粒径小,包封率高,条件易掌握,可作为黄芩苷脂质体的常规制备方法.     

天然大豆磷脂制备热敏脂质体的方法及质量评价

目的：研究用天然磷脂替代合成磷脂制备热敏脂质体的方法及其质量评价。方法：以天然大豆磷脂为主要材料，胆固醇为附加剂，参照均匀设计原理选取影响脂质体热敏性的两个因素：磷脂与胆固醇的比例、制备温度和超声顺序(作为一个因素来考虑)，每个因素选取五个水平进行实验。采用逆相蒸发法制备氟脲脱氧核苷热敏脂质体并对其药物释放量、粒径大小及水中稳定性进行测定。结果：42℃时，药物释放量达到了被包封药物量的88．28％。水中放置4个月基本稳定，渗透率4．5％。结论：天然磷脂能替代合成磷脂制备具有良好相变温度的热敏脂质体。     

药物联合物理疗法治疗MGD所致干眼的疗效观察

目的：比较左氧氟沙星眼凝胶与妥布霉素地塞米松眼膏治疗睑板腺功能障碍(MGD)所致的蒸发过强型干眼的疗效。

方法：将确诊为MGD所致干眼(蒸发过强型)180例360眼患者随机分组。A组应用左氧氟沙星眼凝胶+玻璃酸钠滴眼液治疗; B组采用妥布霉素地塞米松眼膏+玻璃酸钠滴眼液治疗。A、B两组患者均采用综合治疗：用棉棒挤压排出阻塞在睑板腺管内的分泌物,每周1次,连续4wk为一个疗程; 热毛巾湿热敷眼睑,水温45℃左右,每天3次,每次15min,使残留在睑板腺管内的油脂稀薄软化脂质排出。每次眼睑湿热敷完毕后,A组将左氧氟沙星眼凝胶滴入结膜囊内并涂抹在眼睑睫毛根部,B组将妥布霉素地塞米松眼膏涂抹在眼睑睫毛根部,两组患者均滴玻璃酸钠滴眼液每天4次。观察患者术后的疗效。

结果：两组患者治疗后,临床症状评分、分泌物性状评分、泪膜破裂时间评分和泪液分泌试验评分差异均无统计学意义(Z_症状=-0.64,P_症状=0.524; Z_分泌物=-1.37,P_分泌物=0.171; Z_破裂时间=-1.06,P_破裂时间=0.288; Z_分泌时间=-1.06,P_分泌时间=0.288)。角膜荧光染色评分：A组治愈83.3%,好转11.1%,无效5.6%; B组治愈55.6%,好转27.8%,无效16.7%; A组疗效优于B组(Z=-4.02,P<0.001)。

结论：治疗MGD所致的蒸发过强型干眼,以物理疗法为主,药物治疗为辅,除了患病时间长、病情严重的患者可短期使用妥布霉素地塞米松眼膏外,一般均使用左氧氟沙星眼凝胶完全能达到消炎抗菌、安全稳定、无毒副作用的治疗效果,二者药物之间在治疗效果没有明显的差异。     

Vapor condensation with daytime radiative cooling

A radiative vapor condenser sheds heat in the form of infrared radiation and cools itself to below the ambient air temperature to produce liquid water from vapor. This effect has been known for centuries, and is exploited by some insects to survive in dry deserts. Humans have also been using radiative condensation for dew collection. However, all existing radiative vapor condensers must operate during the nighttime. Here, we develop daytime radiative condensers that continue to operate 24 h a day. These daytime radiative condensers can produce water from vapor under direct sunlight, without active consumption of energy. Combined with traditional passive cooling via convection and conduction, radiative cooling can substantially increase the performance of passive vapor condensation, which can be used for passive water extraction and purification technologies.

Energy and clean water are global challenges that are intertwined in an unfavorable way: even in areas where water is abundant, energy may not be available to purify it for human use (1, 2). There has been strong interest in developing passive technologies to purify or harvest water without using fuel or electricity. In this context, passive vapor condensation becomes particularly important because many passive water technologies go through the vapor phase of water in their harvesting or purification processes.Traditional vapor condensation technique is based on convective and conductive heat exchange with ambient environments. This technique is widely used in systems with hot vapors (3–6). However, with ever-increasing emphasis on passive systems, there are many situations in which warm- or even room-temperature vapor needs to be effectively condensed, such as extracting water from atmosphere (7–9) and warm vapor generated from high-efficiency solar evaporation (10). For vapor at such temperatures, most traditional condensers fail. For this reason, there is a clear need for a condensation technique to complement traditional condensers.A different technique is based on radiative vapor condensation. Darkling beetles in the Namib desert (11) use this technique to collect water. Their bodies function as a cooling surface by shedding thermal energy through midinfrared (mid-IR) radiation toward a clear nighttime sky, generating dew from humid air. This mechanism is also used by commercial radiative dew condensers (7–9). However, neither Namib beetle nor existing dew condensers can operate in the daytime (7). Those nighttime radiative condensers are incompatible with many emerging water technologies that require 24 h operation or direct access to sunlight.Recently, Fan et al. showed that passive radiative cooling to subambient temperatures can be realized even during the daytime, by integrating a high-efficiency solar reflector with a high-emissivity thermal emitter in the mid-IR atmospheric transparency window (12). Using this work as a basis, here we demonstrate a daytime radiative condenser. Compared to existing radiative vapor condensers (7–9), our condenser can function even in the presence of sunlight, which is essential for integration into passive water-harvesting systems that mainly operate during daytime.