挤压
差示扫描量热法
乙烯-醋酸乙烯酯
结晶度
溶解
醋酸乙烯酯
材料科学
剂型
化学
聚合物
核化学
化学工程
色谱法
有机化学
复合材料
共聚物
工程类
物理
热力学
作者
A. Almeida,Sam Possemiers,Matthieu N. Boone,Thomas De Beer,Thomas Quinten,Luc Van Hoorebeke,Jean Paul Remon,Chris Vervaet
标识
DOI:10.1016/j.ejpb.2010.12.004
摘要
Different ethylene vinyl acetate grades (EVA9, EVA15, EVA28 and EVA40 having a VA content of 9%, 15%, 28% and 40%, respectively) were characterized via differential scanning calorimetry. Glass transition temperature (T(g)), polymer crystallinity, melting point and polymer flexibility were positively influenced by the vinyl acetate content. The processability of EVA-based formulations produced by means of hot-melt extrusion (2mm die) was evaluated in function of VA content, extrusion temperature (60-140°C) and metoprolol tartrate (MPT, used as model drug) concentration (10-60%). Matrices containing 50% MPT resulted in smooth-surfaced extrudates, whereas at 60% drug content severe surface defects (shark skinning) were observed. Drug release from EVA/MPT matrices (50/50, w/w) was affected by the EVA grades: 90% after 24h for EVA15 and 28, while EVA9 and EVA40 formulations released 80% and 60%, respectively. Drug release also depended on drug loading and extrusion temperature. For all systems, the total matrix porosity (measured by X-ray tomography) was decreased after dissolution due to elastic rearrangement of the polymer. However, the largest porosity reduction was observed for EVA40 matrices as partial melting of the structure (melt onset temperature: 34.7°C) also contributed (thereby reducing the drug release pathway and yielding the lowest release rate from EVA40 formulations). The Simulator of the Human Intestinal Microbial Ecosystem (SHIME) used to evaluate the stability of EVA during gastrointestinal transit showed that EVA was not modified during GI transit, nor did it affect the GI ecosystem following oral administration.
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