Safari Mohammad S, Vorontsova Maria A, Poling-Skutvik Ryan, Vekilov Peter G, Conrad Jacinta C
Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, USA.
Department of Chemistry, University of Houston, Houston, Texas 77204-4004, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2015 Oct;92(4):042712. doi: 10.1103/PhysRevE.92.042712. Epub 2015 Oct 23.
Nanoparticle dynamics impact a wide range of biological transport processes and applications in nanomedicine and natural resource engineering. Differential dynamic microscopy (DDM) was recently developed to quantify the dynamics of submicron particles in solutions from fluctuations of intensity in optical micrographs. Differential dynamic microscopy is well established for monodisperse particle populations, but has not been applied to solutions containing weakly scattering polydisperse biological nanoparticles. Here we use bright-field DDM (BDDM) to measure the dynamics of protein-rich liquid clusters, whose size ranges from tens to hundreds of nanometers and whose total volume fraction is less than 10(-5). With solutions of two proteins, hemoglobin A and lysozyme, we evaluate the cluster diffusion coefficients from the dependence of the diffusive relaxation time on the scattering wave vector. We establish that for weakly scattering populations, an optimal thickness of the sample chamber exists at which the BDDM signal is maximized at the smallest sample volume. The average cluster diffusion coefficient measured using BDDM is consistently lower than that obtained from dynamic light scattering at a scattering angle of 90°. This apparent discrepancy is due to Mie scattering from the polydisperse cluster population, in which larger clusters preferentially scatter more light in the forward direction.
纳米颗粒动力学影响着纳米医学和自然资源工程中广泛的生物传输过程及应用。差分动态显微镜（DDM）是最近开发出来的，用于根据光学显微镜图像强度的波动来量化溶液中亚微米颗粒的动力学。差分动态显微镜对于单分散颗粒群体已经得到了很好的确立，但尚未应用于含有弱散射多分散生物纳米颗粒的溶液。在这里，我们使用明场差分动态显微镜（BDDM）来测量富含蛋白质的液体团簇的动力学，其尺寸范围从几十到几百纳米，总体积分数小于10^(-5)。通过两种蛋白质（血红蛋白A和溶菌酶）的溶液，我们根据扩散弛豫时间对散射波矢的依赖性来评估团簇扩散系数。我们确定，对于弱散射群体，存在一个最佳的样品池厚度，在该厚度下，BDDM信号在最小样品体积时达到最大值。使用BDDM测量的平均团簇扩散系数始终低于在90°散射角下通过动态光散射获得的值。这种明显的差异是由于多分散团簇群体的米氏散射，其中较大的团簇优先向前散射更多的光。
