Imaging Heterogeneous 3D Dynamics of Individual Solutes in a Polyelectrolyte Brush

Abstract

Understanding molecular transport in polyelectrolyte brushes (PEBs) is crucial for applications such as separations, drug delivery, anti-fouling, and biosensors, where structural features of the polymer control intermolecular interactions. The complex structure and local heterogeneity of PEBs, while theoretically predicted, are not easily accessed with conventional experimental methods. In this work, we use 3D single-molecule tracking to understand transport behavior within a cationic poly(2-(N,N-dimethylamino)ethyl acrylate) (PDMAEA) brush using an anionic dye, Alexa Fluor 546, as the probe. The analysis is done by a parallelized, unbiased 3D tracking algorithm. Our results explicitly demonstrate that spatial heterogeneity within the brush manifests as heterogeneity of single-molecule displacements. Two distinct populations of probe motion are identified, with anticorrelated axial and lateral transport confinement, which we believe to correspond to intra-vs inter-chain probe motion.

Variable Non-Gaussian Transport of Nanoplastic on Supported Lipid Bilayers in Saline Conditions

“…Desorption-mediated random walk and confined diffusion are typically observed in single-particle studies on soft polymer surfaces. − Non-Gaussian transport has been observed in various soft-matter systems where the mean square displacement (MSD) is proportional to time but the displacement distribution probability shows convoluted distribution as opposed to a Gaussian curve. , Colloidal particles can follow non-Gaussian type of transport where at short displacements particles show confined motion and at long displacements Brownian diffusion prevails . Transport under a salt environment plays a crucial role in biological systems, and a nanoscale understanding of salt effects on the nanoplastic transport mechanism is lacking.…”