Department of Pharmaceutical Technology and Department of Pharmacognosy and Pharmaceutical Chemistry, Naresuan University, Phitsanulok, Thailand.
Int J Cosmet Sci. 2011 Aug;33(4):351-8. doi: 10.1111/j.1468-2494.2010.00635.x. Epub 2011 Feb 17.
Many effective methods such as spray drying, coacervation, ionic gelation, solvent evaporation and sieving have been suggested for entrapping bioactive compounds into micro- or nanoparticles. However, those methods still have some limitations owing to high temperature requirement, difficulty in particle harvesting or low entrapment for uncharged molecules. In this study, a novel chitosan microparticle preparation method was developed using water-in-silicone emulsion technique with green tea extract as a model active compound. Chitosan microparticles of diameter <5 μm were obtained from 2% chitosan solution with tripolyphosphate (TPP) solution as the hardening agent. The size and properties of the particles appeared to depend on several parameters such as TPP, emulsifier concentrations and pH. High concentration of emulsifier led to low encapsulation and particle aggregation. Entrapment efficiency of chitosan microparticles was improved with lower pH of the tripolyphosphate solution [59.94 ± 3.97 of epigallocatechin gallate (EGCG)] while slowing release of catechins. Epigallocatechin and epicatechin were released almost completely within 2 h under acidic condition whereas EGCG and epicatechin gallate were slowly released. In neutral condition, release of catechins depended on their molecular stabilities. The stabilities of catechins loaded in chitosan microparticles were varied under various temperatures. The degradation of tea catechins increased with temperature. However, the degradation of tea catechins loaded in chitosan microparticles was less than that of free catechins. Thus, the new technique for preparing chitosan microparticles containing heat-sensitive water soluble green tea extract was successfully developed. The technique is suitable for micro-encapsulation of hydrophilic compounds into chitosan microparticles with the ease of harvesting technique.
许多有效的方法，如喷雾干燥、凝聚、离子凝胶化、溶剂蒸发和筛分，已经被提出用于将生物活性化合物包埋入微纳米颗粒中。然而，由于需要高温、颗粒收集困难或对不带电荷的分子包埋效率低，这些方法仍然存在一些局限性。在这项研究中，使用水包硅乳液技术开发了一种新型壳聚糖微球制备方法，以绿茶提取物为模型活性化合物。通过 2%壳聚糖溶液和三聚磷酸钠（TPP）溶液作为硬化剂，获得了直径<5 μm 的壳聚糖微球。颗粒的大小和性质似乎取决于 TPP、乳化剂浓度和 pH 等几个参数。高浓度的乳化剂会导致包封率低和颗粒聚集。TPP 溶液的 pH 值较低时（[59.94±3.97]的表没食子儿茶素没食子酸酯（EGCG）），壳聚糖微球的包埋效率提高，儿茶素的释放速度减慢。在酸性条件下，表没食子儿茶素和表儿茶素几乎在 2 小时内完全释放，而 EGCG 和表儿茶素没食子酸酯则缓慢释放。在中性条件下，儿茶素的释放取决于其分子稳定性。在不同温度下，负载在壳聚糖微球中的儿茶素的稳定性也有所不同。儿茶素的降解随温度升高而增加。然而，负载在壳聚糖微球中的儿茶素的降解速度低于游离儿茶素。因此，成功开发了一种用于制备含有热敏性水溶性绿茶提取物的壳聚糖微球的新技术。该技术适用于将亲水性化合物包埋到壳聚糖微球中，且易于进行颗粒收集。
