单凝聚与复凝聚法制备昆虫激素十二醇微胶囊及其释放行为

通过向明胶溶液中加入硫酸钠溶液的单凝聚方法以及将明胶溶液加入到阿拉伯胶溶液的复凝聚方法,制备了聚合物包覆昆虫激素十二醇的水分散体系微胶囊.通过对凝聚过程中ζ电位与透光率跟踪测试确定了单凝聚中加入硫酸钠的最佳用量以及复凝聚中明胶与阿拉伯胶的相对量.在壁材浓度大于或等于3%条件下制备的复凝聚胶囊的尺寸大于单凝聚微胶囊,但后者的大小分布更均一.除非在2%壁材浓度下,其他条件下复凝聚制备的胶囊的十二醇包覆率明显高于单凝聚胶囊.对胶囊中十二醇在恒湿恒温条件下的释放研究表明,单凝聚胶囊中十二醇很快释放完毕,变化壁材浓度不明显改变其释放行为.相比之下复凝聚胶囊中十二醇的释放对壁材浓度有明显的依赖性.2%壁材浓度制备的胶囊其释放行为类似于单凝聚胶囊;但3%到5%壁材浓度制备的胶囊中十二醇的释放明显分为3个区间,即较快的初始释放、较长时间的恒速释放以及最后阶段释放速率的再次提高直至释放完毕.复凝聚胶囊中十二醇的释放表现出了明显的可控性.文中亦对该体系中昆虫激素十二醇的释放机理作了初步讨论.

PREPARATION OF INSECT SEX PHEROMONE DODECANOL CONTAINING MICROCAPSULES BY SIMPLE AND COMPLEX COACERVATIONS AND THEIR RELEASE BEHAVIOR

Microcapsules with dodecanol(C_ 12OH)encapsulated were prepared through complex coacervation by adding gelatin(GE)solution to an acacia gum(AG)solution and through GE simple coacervation by adding sodium sulfate solution to GE solution,both in presence of C_ 12OH.C_ 12OH was chosen for the core material because it does constitute a real component in sex pheromones of numerous insects.In a first step,Zeta potential and light transmittance in the two coacervation processes were followed in order to determine the optimum ratio of AG and GE in complex coacervation and the best amount of sodium sulfate in simple coacervation.It was observed that maximum yield was achieved for complex coacervation with AG/GE weight ratio at unity,and for simple coacervation when 30 mL of 20% sodium sulfate was added to 40 mL of 6% GE solution.When the wall material concentration was equal to or higher than 3%,the size of the microcapsules from complex coacervation was larger than that prepared through simple coacervation.Nevertheless,simple coacervation led to capsules with much narrower size distribution.C_ 12OH encapsulation rates in simple coacervation were significantly lower compared with those in complex coacervation at equal wall material concentration,leading therefore to a lower C_ 12OH loading in simple coacervation.To investigate C_ 12OH release from the capsules,samples were placed into an incubator with constant temperature(30℃)and relative humidity(50% RH),and taken out for C_ 12OH examination by gas chromatography and by weighing the samples.It was found that all samples from simple coacervation reached their final release in less than one week,no difference was observed for samples prepared with different wall material concentration;whereas microcapsules from complex coacervation manifested a three-step-release profile,i.e.a quick start followed by a constant plateau region and terminated by a release increase till completion.Results also revealed that capsules prepared with higher wall material concentration had a higher release rates.The capsules prepared with 5% solutions of AG and GE lost their C_ 12OH within 2 weeks;lowering wall material concentration effectively reduced C_ 12OH release rate and extended C_ 12OH constant release period.This work indicates that release of C_ 12OH can be well controlled through capsule structure designing.This is of great importance for our on-going study on controlled release of authentic insect semiochemicals.