Elkharraz K, Dashevsky A, Bodmeier R
College of Pharmacy, Freie Universität Berlin, Germany.
J Microencapsul. 2003 Sep-Oct;20(5):661-73. doi: 10.1080/0265204031000151965.
Microparticles were prepared by a film grinding method, whereby thin drug-containing ethylcellulose films were cryogenically ground into microparticles. The particle size and shape of the microparticles could be controlled by the thickness of the films and by the milling time. The encapsulation efficiency as well as the in vitro drug release depended on the physical state of the drug in the ethylcellulose matrix (dispersed vs dissolved). Increased drug loadings and decreased particle size and film thickness increased the drug release. Microparticles prepared from cast films were more dense and had a slower drug release compared to microparticles prepared from sprayed films or from films prepared from an aqueous colloidal ethylcellulose dispersion, Aquacoat ECD. Lamination of the drug-containing film with a drug-free polymer layer on both sides resulted in a reduced drug release. Hydrophilic plasticizers acted as pore-formers and accelerated drug release, while lipophilic plasticizers reduced the drug release. The solubility of the drug in the organic polymer solution was one of the main parameters to achieve high encapsulation efficiencies and extended drug release, while dispersed drug was released much faster. The drug release from microparticles prepared by film grinding was faster than from microparticles prepared by the solvent evaporation method. The faster release was attributed to the fractured surface of the ground particles. Grinding of microparticles, which were prepared by the solvent evaporation, also resulted in a faster release.
通过薄膜研磨法制备微粒，即将含药的乙基纤维素薄膜进行低温研磨成微粒。微粒的粒径和形状可通过薄膜厚度和研磨时间来控制。包封率以及体外药物释放取决于药物在乙基纤维素基质中的物理状态（分散态与溶解态）。增加药物载量、减小粒径和薄膜厚度会加快药物释放。与由喷雾薄膜或由水性胶体乙基纤维素分散体（Aquacoat ECD）制备的薄膜所制备的微粒相比，由流延薄膜制备的微粒更致密且药物释放更慢。在含药薄膜两侧用不含药物的聚合物层进行层压会导致药物释放减少。亲水性增塑剂充当成孔剂并加速药物释放，而亲脂性增塑剂则降低药物释放。药物在有机聚合物溶液中的溶解度是实现高包封率和延长药物释放的主要参数之一，而分散的药物释放得更快。通过薄膜研磨制备的微粒的药物释放比通过溶剂蒸发法制备的微粒更快。更快的释放归因于研磨颗粒的破裂表面。对通过溶剂蒸发制备的微粒进行研磨也会导致更快的释放。
