Chognot David, Léonard Michèle, Six Jean-Luc, Dellacherie Edith
Laboratoire de Chimie Physique Macromoléculaire, UMR CNRS-INPL 7568, ENSIC, BP 20451, 54001 Nancy Cedex, France.
Colloids Surf B Biointerfaces. 2006 Aug 1;51(1):86-92. doi: 10.1016/j.colsurfb.2006.04.003. Epub 2006 May 2.
We have already shown that polylactide (PLA) nanoparticles covered with a hydrophilic polymeric layer can be prepared by simple emulsion/solvent evaporation by using amphiphilic copolymers as surfactants during the procedure. The external layer is then constituted by the hydrophilic part of the macromolecular surfactant. This kind of nanospheres is useful for the encapsulation of lipohilic molecules. The use of amphiphilic copolymers as surfactants in the preparation of PLA nanospheres with controlled surface properties, was then applied to the double emulsion/solvent evaporation procedure. The aim was to allow the encapsulation of water-soluble bioactive molecules in PLA particles with controlled surface properties. In this paper, we describe the results obtained with three different water-soluble monomethoxypolyethylene oxide (MPEO)-b-PLA diblock copolymers used as surfactants in the preparation of nanoparticles by double emulsion/solvent evaporation. After organic solvent evaporation, the obtained nanospheres were proved to be really covered by a MPEO layer whose characteristics were determined. It was firstly shown that the MPEO-covered particles did not flocculate at 25 degrees C, even in 4 M NaCl while suspensions of bare nanospheres were destabilized for a NaCl concentration as low as 0.04 M. On the other hand, the suspensions of MPEO-covered nanoparticles in 0.3 M Na2SO4 were found to be very sensitive to temperature as they flocculated at a temperature lying between 45 and 55 degrees C depending on the MPEO-b-PLA composition. This property was attributed to the fact that MPEO is a polymer with a low critical solution temperature. The concentration of MPEO at the nanoparticle surface was then calculated for the three kinds of particles, from the initial flocculation temperature, and was found to be comparable to the value determined directly.
我们已经表明，在该过程中使用两亲性共聚物作为表面活性剂，通过简单的乳液/溶剂蒸发法可以制备覆盖有亲水性聚合物层的聚丙交酯（PLA）纳米颗粒。然后，外层由大分子表面活性剂的亲水性部分构成。这种纳米球可用于包封亲脂性分子。将两亲性共聚物作为表面活性剂用于制备具有可控表面性质的PLA纳米球，随后应用于双乳液/溶剂蒸发法。目的是将水溶性生物活性分子包封在具有可控表面性质的PLA颗粒中。在本文中，我们描述了在双乳液/溶剂蒸发法制备纳米颗粒过程中，使用三种不同的水溶性单甲氧基聚环氧乙烷（MPEO）-b-PLA二嵌段共聚物作为表面活性剂所获得的结果。有机溶剂蒸发后，所得到的纳米球被证明确实被一层MPEO层覆盖，并且测定了其特性。首先表明，即使在4M NaCl中，在25℃下MPEO覆盖的颗粒也不会絮凝，而裸露纳米球的悬浮液在NaCl浓度低至0.04M时就会失稳。另一方面，发现MPEO覆盖的纳米颗粒在0.3M Na2SO4中的悬浮液对温度非常敏感，因为它们在45至55℃之间的某个温度下会絮凝，具体取决于MPEO-b-PLA的组成。这种性质归因于MPEO是一种具有低临界溶液温度的聚合物。然后根据初始絮凝温度计算了三种颗粒在纳米颗粒表面的MPEO浓度，发现其与直接测定的值相当。
