Transport Properties of Hydrogels with Structural Anisotropy

Structural anisotropy is a hallmark of biological networks, as it regulates transport of ions, nutrients, and metabolites. Understanding the role of structural anisotropy is crucial for elucidating transport of biologically important species, e.g., the delivery of drugs to a diseased location or migration of metastasis-associated molecules.

Here, we used extrusion-based 3D printing to fabricate structurally anisotropic fibrous hydrogels in microfluidic channels and explore their transport properties. Fiber orientation was controlled by varying the extrusion pressure and direction relative to the long microchannel axis. The effect of hydrogel structure was studied for diffusion- and advection-driven transport of nanoparticle probes with varying dimensions. For both diffusion- and advection-driven transport, probe motion was enhanced along the direction of fiber alignment, which was attributed to reduced probability of probe–fiber collisions. This effect became more prominent for larger probes. Fluid dynamics simulations reproduced the experimental results. Together, these findings provide a mechanistic insight into how molecules and nanoparticle move through structurally anisotropic fibrous tissues.