Schatz Christophe, Lucas Jean-Michel, Viton Christophe, Domard Alain, Pichot Christian, Delair Thierry
Unité mixte CNRS-BioMérieux, UMR 2142, ENS Lyon, 46, allée d'Italie, 69364 Lyon Cedex 07, France.
Langmuir. 2004 Aug 31;20(18):7766-78. doi: 10.1021/la049460m.
Formation of colloids based on polyelectrolyte complexes (PECs) was mainly studied with synthetic polyelectrolytes. In this study, we describe the elaboration of positively charged PEC particles at a submicrometer level obtained by the complexation between two charged polysaccharides, chitosan as polycation and dextran sulfate (DS) as polyanion. The complexes were elaborated by dropwise addition of default amounts of DS to excess chitosan. Quasi-elastic light scattering was used to investigate in detail the influence of the characteristics of components (chain length, degree of acetylation) and parameters linked to the reaction of complexation (molar mixing ratio, ionic strength, concentration in polymer) on the sizes and polydispersity of colloids. Chain length of chitosan is the major parameter affecting the dimensions of the complexes, high molar mass chitosans leading to the largest particles. Variations of hydrodynamic diameters of PECs with the molar mass of chitosan are consistent with a mechanism of particle formation through the segregation of the neutral and then hydrophobic blocks of the polyelectrolyte complexed segments. Resulting particles display probably a structure constituted by a neutral core surrounded by a chitosan shell ensuring the colloidal stabilization. Such a structure was evidenced by measurements of electrophoretic mobilities revealing that the positive charge of particles was decreasing with pH, in relation with the neutralization of excess glucosamine hydrochloride moieties.
基于聚电解质复合物（PEC）的胶体形成主要是用合成聚电解质进行研究的。在本研究中，我们描述了通过两种带电多糖（作为聚阳离子的壳聚糖和作为聚阴离子的硫酸葡聚糖（DS））之间的络合作用，在亚微米水平上制备带正电荷的PEC颗粒。通过向过量的壳聚糖中逐滴加入规定量的DS来制备复合物。利用准弹性光散射详细研究了组分特性（链长、乙酰化程度）以及与络合反应相关的参数（摩尔混合比、离子强度、聚合物浓度）对胶体尺寸和多分散性的影响。壳聚糖的链长是影响复合物尺寸的主要参数，高分子量的壳聚糖会形成最大的颗粒。PEC的流体动力学直径随壳聚糖摩尔质量的变化与通过聚电解质络合链段的中性和疏水嵌段的分离形成颗粒的机制一致。所得颗粒可能呈现出由中性核和包围它的壳聚糖壳组成的结构，壳聚糖壳确保了胶体的稳定性。通过测量电泳迁移率证明了这种结构，结果表明颗粒的正电荷随pH值降低，这与过量的盐酸氨基葡萄糖部分的中和有关。
