Anomalous Confined Diffusion of Nanoparticles in Polymer Solutions

Nanoparticle diffusion in complex physiological media plays an important role in the processes of life evolution, information transmission and drug delivery. Different from the classical Brownian motion in the pure fluids, the diffusion in physiological media is often confined and shows anomalous behavior. In this study, we experimentally study the confined diffusion of nanoparticles in polyethylene oxide solutions based on particle tracking method. By inspecting the ensemble-averaged mean square displacement, the non-Gaussian parameter and the displacement probability density, the anomalies are identified as the sub-diffusive behavior at short times and the non-Gaussianity at long times. The time-averaged mean square displacement and the ergodicity breaking parameters are then examined, and the origin of the non-Gaussian anomaly at long times are elucidated as the non-ergodicity. The present results offer us a more comprehensive understanding of anomalous confined diffusion in complex media and may provide theoretical guidance for regulating drug delivery and optimizing drug design.