Fachbereich für Physik , Freie Universität Berlin , 14195 Berlin , Germany.
Department of Chemistry , University of Kentucky , Lexington , Kentucky 40506 , United States.
Nano Lett. 2018 Aug 8;18(8):5248-5256. doi: 10.1021/acs.nanolett.8b02218. Epub 2018 Jul 5.
All biogels are heterogeneous, consisting of functional groups with different biophysical properties arrayed on spatially disordered polymer networks. Nanoparticles diffusing in such biogels experience a mixture of attractive and repulsive interactions. Here, we present experimental and theoretical studies of charged particle diffusion in gels with a random distribution of attractive and repulsive electrostatic interaction sites inside the gel. In addition to interaction disorder, we theoretically investigate the effect of spatial disorder of the polymer network. Our coarse-grained simulations reveal that attractive interactions primarily determine the diffusive behavior of the particles in systems with mixed attractive and repulsive interactions. As a consequence, charged particles of either sign are immobilized in mixed cationic/anionic gels because they are trapped near oppositely charged interaction sites, whereas neutral particles diffuse rapidly. Even small fractions of oppositely charged interaction sites lead to strong trapping of a charged particle. Translational diffusion coefficients of charged probe molecules in gels consisting of mixed cationic and anionic dextran polymers are determined by fluorescence correlation spectroscopy and quantitatively confirm our theoretical predictions.
所有生物凝胶都是不均匀的，由具有不同生物物理性质的官能团排列在空间无序的聚合物网络上组成。在这种生物凝胶中扩散的纳米粒子会经历吸引力和排斥力的混合相互作用。在这里，我们提出了在凝胶中存在吸引力和排斥力静电相互作用位置随机分布的情况下，带电粒子在凝胶中扩散的实验和理论研究。除了相互作用无序之外，我们还从理论上研究了聚合物网络空间无序的影响。我们的粗粒化模拟表明，吸引力相互作用主要决定了混合吸引和排斥相互作用系统中粒子的扩散行为。因此，带正负电荷的粒子都被固定在混合阳离子/阴离子凝胶中，因为它们被束缚在带相反电荷的相互作用位置附近，而中性粒子则快速扩散。即使只有一小部分带相反电荷的相互作用位置也会导致带电粒子的强烈捕获。通过荧光相关光谱法确定了由混合阳离子和阴离子葡聚糖聚合物组成的凝胶中带电探针分子的平移扩散系数，并定量证实了我们的理论预测。
