Size control of therapeutic carriers in drug delivery systems has become important due to its relevance to biodistribution in the human body and therapeutic efficacy. To understand the dependence of particle size on the formation condition during nanoprecipitation method, we prepared nanoparticles from biodegradable, amphiphilic block copolymers and investigated the particle size and structure of the resultant nanoparticles according to various process parameters. We synthesized monomethoxy poly(ethylene glycol)-poly(ε-caprolactone) block copolymer, MPEG-PCL, with different MPEG/PCL ratios via ring opening polymerization initiated from the hydroxyl end group of MPEG. Using various formulations with systematic change of the block ratio of MPEG and PCL, solvent choice, and concentration of organic phase, MPEG-PCL nanoparticles were prepared through nanoprecipitation technique. The results indicated that (i) the nanoparticles have a dual structure with an MPEG shell and a PCL core, originating from self-assembly of MPEG-PCL copolymer in aqueous condition, and (ii) the size of nanoparticles is dependent upon two sequential processes: diffusion between the organic and aqueous phases and solidification of the polymer.

中文翻译：

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纳米沉淀法形成聚乙二醇-聚己内酯纳米粒子

由于其与人体中生物分布和治疗功效的相关性，药物输送系统中治疗载体的尺寸控制已变得重要。为了了解纳米沉淀法中粒径对形成条件的依赖性，我们从可生物降解的两亲嵌段共聚物制备了纳米颗粒，并根据各种工艺参数研究了所得纳米颗粒的粒径和结构。我们通过由MPEG的羟基端基引发的开环聚合反应，合成了具有不同MPEG / PCL比的单甲氧基聚（乙二醇）-聚（ε-己内酯）嵌段共聚物MPEG-PCL。使用各种配方，系统地改变MPEG和PCL的嵌段比例，溶剂的选择以及有机相的浓度，通过纳米沉淀技术制备了MPEG-PCL纳米颗粒。结果表明：（i）纳米颗粒具有MPEG壳和PCL核的双重结构，源于在水性条件下MPEG-PCL共聚物的自组装，并且（ii）纳米颗粒的大小取决于两个顺序的过程：有机相和水相之间的扩散以及聚合物的固化。