Gelation of microemulsions and release behavior of sodium salicylate from gelled microemulsions

A novel gelled microemulsion was prepared in the presence of the low molecular weight gelator N-stearine-N′-stearyl-l-phenylalanine at a very low concentration. It is completely different from the conventional microemulsion-based gels (MBGs) usually formed by polymeric gelling agents, such as gelatin, agar and κ-carrageenan. The microemulsion consists of i-propyl myristate, Tween 80, propylene glycol and water. The gelled microemulsions showed good thermo-reversibility. The gel-to-sol transition temperature (T_GS) of gelled microemulsion depends upon the concentration of gelator and the composition of the microemulsions. The gelation mechanism was investigated by polarized optical microscopy (POM) and FT-IR. POM images show elongated and strand-like crystallites formed by the aggregation of the gelator, ultimately resulting in the gelation of the microemulsion. FT-IR analysis indicates that intermolecular hydrogen bonds are responsible for the formation of gelator aggregates. Water-soluble sodium salicylate was used as a model drug for the investigation of the release from the gelled microemulsions. The release profiles exhibited a controlled release and followed the first-order release kinetics. The release rates decreased with an increase of the gelator and isopropyl myristate contents. These results reveal potential applications of gelled microemulsion in drug delivery systems.     

利培酮有机原位凝胶的制备及其体外评价

目的 以利培酮为模型药物,制备利培酮有机原位凝胶.方法 通过考察凝胶因子和抗凝剂对药物在体内外的释放及相关性的影响,确定最佳的制剂处方.结果 注射用大豆油为凝胶基质,12.5％的硬脂酸为凝胶因子,NMP为抗凝剂制备的液态载药有机原位凝胶,在37℃下的体外释放周期约为72 h,体内结果与体外的基本一致.注射予大鼠,无明显的炎症反应.结论 利培酮有机原位凝胶是可以延长药物释放周期的新剂型.     

Host-guest interactions of 5-fluorouracil in supramolecular organogels

Supramolecular organogels were formed by the self-assembly of gelator 1,3:2,4-di-O-benzylidene-d-sorbitol (DBS) in 1,2-propylene glycol. 5-Fluorouracil (5-Fu) was entrapped in the organogels as guest molecules. Field-emission scanning electron microscopic measurements of the organogels indicate that the diameters of the fibrillar aggregates formed by DBS self-assembly were in the range of 20-70 nm. The host-guest interactions between 5-Fu and supramolecular gel matrix were investigated by using temperature-dependent differential UV spectroscopy and differential scanning calorimetry. The red shifts of the absorption band of 5-Fu in the organogels are indicative of the interaction between 5-Fu and DBS. The red shifts were enhanced upon decreasing the temperature. Calculation of optimized geometries revealed the formation of hydrogen bonds between 5-Fu and DBS aggregates. The analysis of differential scanning calorimetric data for the organogels with and without 5-Fu further showed that the self-assembly of DBS was interfered by the 5-Fu in the organogels, resulting in a decrease in the dissociating temperature of DBS aggregates.