Department of Applied Physics, Eindhoven University of Technology (TU/e) , Eindhoven 5600 MB, The Netherlands.
Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology (TU/e) , Eindhoven 5600 MB, The Netherlands.
ACS Nano. 2016 Mar 22;10(3):3093-101. doi: 10.1021/acsnano.5b07021. Epub 2016 Mar 1.
Biofunctionalized colloidal particles are widely used as labels in bioanalytical assays, lab-on-chip devices, biophysical research, and in studies on live biological systems. With detection resolution going down to the level of single particles and single molecules, understanding the nature of the interaction of the particles with surfaces and substrates becomes of paramount importance. Here, we present a comprehensive study of motion patterns of colloidal particles maintained in close proximity to a substrate by short molecular tethers (40 nm). The motion of the particles (500-1000 nm) was optically tracked with a very high localization accuracy (below 3 nm). A surprisingly large variation in motion patterns was observed, which can be attributed to properties of the particle-molecule-substrate system, namely the bond number, the nature of the bond, particle protrusions, and substrate nonuniformities. Experimentally observed motion patterns were compared to numerical Monte Carlo simulations, revealing a close correspondence between the observed motion patterns and properties of the molecular system. Particles bound via single tethers show distinct disc-, ring-, and bell-shaped motion patterns, where the ring- and bell-shaped patterns are caused by protrusions on the particle in the direct vicinity of the molecular attachment point. Double and triple tethered particles exhibit stripe-shaped and triangular-shaped motion patterns, respectively. The developed motion pattern analysis allows for discrimination between particles bound by different bond types, which opens the possibility to improve the limit of detection and the dynamic range of bioanalytical assays, with a projected increase of dynamic range by nearly 2 orders of magnitude.
生物功能化胶体颗粒被广泛用作生物分析测定、芯片实验室设备、生物物理研究以及活体生物系统研究中的标记物。随着检测分辨率降低到单个颗粒和单个分子的水平，理解颗粒与表面和基底相互作用的性质变得至关重要。在这里，我们对通过短分子键（40nm）保持在靠近基底的胶体颗粒的运动模式进行了全面研究。使用非常高的定位精度（低于 3nm）通过光学跟踪颗粒（500-1000nm）的运动。观察到运动模式的惊人变化，可以归因于颗粒-分子-基底系统的性质，即键数、键的性质、颗粒突出部分和基底非均匀性。将实验观察到的运动模式与数值蒙特卡罗模拟进行比较，揭示了观察到的运动模式与分子系统性质之间的密切对应关系。通过单个键结合的颗粒表现出明显的盘状、环状和钟形运动模式，其中环状和钟形运动模式是由分子附着点附近的颗粒突起引起的。双和三键合的颗粒分别表现出条纹状和三角形运动模式。开发的运动模式分析允许区分不同键合类型结合的颗粒，这为提高生物分析测定的检测限和动态范围提供了可能性，预计动态范围将增加近 2 个数量级。
