Rollié Sascha, Sundmacher Kai
Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstrasse 1, 39106 Magdeburg, Germany.
Langmuir. 2008 Dec 2;24(23):13348-58. doi: 10.1021/la8024765.
Cluster composition in aggregation processes of multiple particle species can be dynamically determined by flow cytometry if particle populations are fluorescently labeled. By flow cytometric single particle analysis, aggregates can be characterized according to the exact amount of constituent particles, allowing the detailed and separate quantification of homo- and heteroaggregation. This contribution demonstrates the application of flow cytometry for the experimental detection of heteroaggregation in a binary particle mixture of oppositely charged polystyrene (PS) particles and Rhodamine-B labeled melamine-formaldehyde (MF-RhB) particles. Experiments with different particle concentration, temperature, mixing mode, ionic strength and particle mixing ratio are presented. Aggregation kinetics are enhanced with increasing particle concentration and temperature as well as by increased shear of mixing. These results represent well-known behavior published in previous investigations and validate the performance of flow cytometry for probing heteroaggregation processes. Physical insight with a novel level of detail is gained by the quantification of de- and restabilization phenomena. At low ionic strength, "raspberry"-type aggregates with PS cores are formed by primary heteroaggregation. At moderate particle number ratios, these aggregates are electrostatically destabilized and form more complex aggregates in a secondary heteroaggregation process. At high particle number ratios (> or =50:1), the raspberry-type aggregates are electrostatically restabilized and secondary heteroaggregation is prevented. The dynamic change of aggregate charge was verified by zeta-potential measurements. The elevation of salt concentration over several orders of magnitude retards aggregation dynamics, since attractive interparticle forces are diminished by an electrostatic double layer. This indicates that heteroaggregation induced by attractive interparticle forces is faster than aggregation due to random Brownian motion. Destabilization at high ionic strength is facilitated by charged ions and no longer by MF-RhB coverage. This results in a species independent one step aggregation process.
如果粒子群体经过荧光标记，那么在多粒子种类的聚集过程中，簇组成可以通过流式细胞术动态测定。通过流式细胞术单粒子分析，聚集体可以根据组成粒子的确切数量来表征，从而实现对同聚和异聚的详细且单独的定量分析。本论文展示了流式细胞术在实验检测带相反电荷的聚苯乙烯（PS）颗粒与罗丹明-B标记的三聚氰胺-甲醛（MF-RhB）颗粒的二元粒子混合物中的异聚作用。文中给出了不同粒子浓度、温度、混合模式、离子强度和粒子混合比例的实验结果。随着粒子浓度、温度的增加以及混合剪切力的增大，聚集动力学增强。这些结果体现了先前研究中已公布的众所周知的行为，并验证了流式细胞术探测异聚过程的性能。通过对去稳定和再稳定现象的定量分析，获得了具有全新详细程度的物理见解。在低离子强度下，通过初级异聚作用形成了以PS为核心的“覆盆子”型聚集体。在中等粒子数比例下，这些聚集体发生静电去稳定，并在二级异聚过程中形成更复杂的聚集体。在高粒子数比例（≥50:1）时，“覆盆子”型聚集体发生静电再稳定，从而阻止了二级异聚作用。通过zeta电位测量验证了聚集体电荷的动态变化。盐浓度在几个数量级上的升高会延缓聚集动力学，因为粒子间的吸引力会因静电双层而减弱。这表明由粒子间吸引力诱导的异聚作用比随机布朗运动引起的聚集作用更快。在高离子强度下，去稳定作用由带电离子促进，而不再由MF-RhB覆盖促进。这导致了一个与物种无关的一步聚集过程。
