State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China.
School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian, Liaoning 116024, China.
Nano Lett. 2020 May 13;20(5):3895-3904. doi: 10.1021/acs.nanolett.0c01058. Epub 2020 Apr 2.
A long-distance hop of diffusive nanoparticles (NPs) in crowded environments was commonly considered unlikely, and its characteristics remain unclear. In this work, we experimentally identify the occurrence of the intermittent hops of large NPs in crowded entangled poly(ethylene oxide) (PEO) solutions, which are attributed to thermally induced activated hopping. We show that the diffusion of NPs in crowded solutions is considered as a superposition of the activated hopping and the reptation of the polymer solution. Such activated hopping becomes significant when either the PEO molecular weight is large enough or the NP size is relatively small. We reveal that the time-dependent non-Gaussianity of the NP diffusion is determined by the competition of the short-time relaxation of a polymer entanglement strand, the activated hopping, and the long-time reptation. We propose an exponential scaling law τ/τ ∼ exp(/) to characterize the hopping time scale, suggesting a linear dependence of the activated hopping energy barrier on the dimensionless NP size. The activated hopping motion can only be observed between the onset time scale of the short-time relaxation of local entanglement strands and the termination time scale of the long-time relaxation. Our findings on activated hopping provide new insights into long-distance transportation of NPs in crowded biological environments, which is essential to the delivery and targeting of nanomedicines.
扩散纳米颗粒（NPs）在拥挤环境中的远距离跳跃通常被认为是不可能的，其特性仍不清楚。在这项工作中，我们通过实验确定了大 NPs 在拥挤的缠结聚环氧乙烷（PEO）溶液中间歇性跳跃的发生，这归因于热诱导的激活跳跃。我们表明，NP 在拥挤溶液中的扩散被认为是激活跳跃和聚合物溶液的蠕动的叠加。当 PEO 分子量足够大或 NP 尺寸相对较小时，这种激活跳跃变得很重要。我们揭示了 NP 扩散的时变非高斯性由聚合物缠结链的短时间松弛、激活跳跃和长时间蠕动的竞争决定。我们提出了一个指数标度律 τ/τ∼exp(/)来描述跳跃时间尺度，表明激活跳跃能垒与无量纲 NP 尺寸呈线性关系。激活跳跃运动只能在局部缠结链的短时间松弛的起始时间尺度和长时间松弛的终止时间尺度之间观察到。我们对激活跳跃的研究结果为 NP 在拥挤的生物环境中的远距离运输提供了新的见解，这对于纳米药物的输送和靶向至关重要。
