Tissues and individual cells are poroelastic, consisting of a background matrix suffused by solvent carrying solutes of varying sizes. In vivo , materials undergo dynamic stresses, causing deformations which induce advection and size-dependent transport. Solute distribution in the nucleus, a heterogeneous poroelastic environment under dynamic strains, drives gene transcription. Experiments examining the macroscale dynamics of poroelastic media demonstrate enhanced concentration of large solutes in cyclically strained hydrogels, but there remains a dearth of studies probing the intricate interactions between solutes, pores, stress gradients, and microfluidics during dynamic strains; thus, the roots of these emergent behaviors remain unclear. Non-Gaussian diffusion in poroelastic media is temporally anisotropic, converging to Gaussian behavior over time. Using highly inclined laminated optical sheet microscopy, we conduct single particle tracking of quantum dots at up to 900 frames per second, allowing for unprecedented spatiotemporal resolution during single particle tracking. Using this technique, we study trapping time distributions and intra-pore behaviors of localized particles in polyacrylamide and tetra-PEG gels. Conducting single particle tracking in polyacrylamide gel during microscale dynamic strains reveals significant impacts on large-solute transport. Both static and dynamic strains increase long-term localization and decrease diffusivity compared to unstrained controls, mimicking the behavior of gels with a smaller pore size. Strains also enhance the magnitude and duration of non-Gaussian behaviors in the specimen. Dynamic strains induce advective transport of large solutes during compression and relaxation. Dynamic strains reduce long-term solute localization asymmetrically throughout their cycle by as much as a factor of three compared to static strains of the same or inferior magnitude, with fewer particles localizing during maximum strain than minimum strain. This asymmetry offers a potential nanoscopic explanation for the reported pumping effect of dynamic strains on large solutes in poroelastic media.
Marshall et al. (Sun,) studied this question.