Farahmand S, Tajerzadeh H, Farboud E S
College of Pharmacy, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Pharm Dev Technol. 2006;11(2):255-61. doi: 10.1080/10837450500464172.
Multiple phase emulsions are increasingly used as alternatives to simple emulsions in personal care products. One of the major advantages of these emulsions over simple emulsions is slow and controlled release of their ingredients. Other favorite cosmetic characteristics of multiple emulsions include occlusivity (in O/W/O emulsions), esthetics and consumer acceptance. Vitamin C (ascorbic acid) has been widely used in formulations of skin care products. Due to its effects on collagen biosynthesis, it is considered as moisturizing and anti-aging active ingredient. Instability problems such as oxidation susceptibility have made incorporating vitamin C in topical formulations a challenging issue. The O/W/O emulsions have been formulated using two-step procedure, to investigate vitamin C stability and its release profile. By using different surfactant types and ratios, volume ratio of phases, multiple emulsions containing vitamin C were prepared. Different parameters and formulation factors such as temperature of phases, duration and speed of mixing were evaluated. Based on our results, more stable emulsions were prepared from non-ionic siliconized surfactants, sorbitan derivatives and co-surfactants such as polyglyceryl derivatives. Physical stability was determined by microscopic examination, centrifugation and incubating emulsions in different temperatures. Vitamin C in vitro release studies from O/W and O/W/O emulsions were conducted using Franz diffusion cell (at room temperature) and UV spectrophotometry. The results showed that in the first four-hour period, about 14% of vitamin C released from O/W/O emulsions. It appears that in multiple emulsions the profile of release follows zero-order kinetics. Our data indicate that incorporating vitamin C in multiple emulsions significantly increased its stability possibly attributed to the formation of reverse micelles of surfactants (and/or co-surfactants), which entrapped vitamin C inside the micelles surrounded by hydrophilic heads of surfactant. Moreover, vitamin C was released from multiple emulsions in a zero order slow and controlled release manner.
多重乳液在个人护理产品中越来越多地被用作简单乳液的替代品。与简单乳液相比，这些乳液的主要优点之一是其成分的缓慢和可控释放。多重乳液的其他受欢迎的化妆品特性包括封闭性（在O/W/O乳液中）、美学效果和消费者接受度。维生素C（抗坏血酸）已广泛用于护肤品配方中。由于其对胶原蛋白生物合成的作用，它被认为是一种保湿和抗老化活性成分。诸如氧化敏感性等稳定性问题使得将维生素C纳入局部配方成为一个具有挑战性的问题。采用两步法制备了O/W/O乳液，以研究维生素C的稳定性及其释放曲线。通过使用不同类型和比例的表面活性剂、相的体积比，制备了含有维生素C的多重乳液。评估了不同参数和配方因素，如相的温度、混合持续时间和速度。根据我们的结果，由非离子硅化表面活性剂、脱水山梨醇衍生物和辅助表面活性剂（如聚甘油衍生物）制备的乳液更稳定。通过显微镜检查、离心和在不同温度下孵育乳液来确定物理稳定性。使用Franz扩散池（在室温下）和紫外分光光度法对O/W和O/W/O乳液中的维生素C进行体外释放研究。结果表明，在最初的四个小时内，约14%的维生素C从O/W/O乳液中释放出来。似乎在多重乳液中，释放曲线遵循零级动力学。我们的数据表明，将维生素C纳入多重乳液中显著提高了其稳定性，这可能归因于表面活性剂（和/或辅助表面活性剂）反胶束的形成，反胶束将维生素C包裹在由表面活性剂亲水头部包围的胶束内部。此外，维生素C以零级缓慢且可控的释放方式从多重乳液中释放出来。
