Ring-Shaped Open Microfluidic Platform Reveals Viscosity-Driven Mechanical Priming of Glioblastoma Cells

The glioblastoma (GBM) tumor microenvironment is characterized by abnormally high extracellular viscosity, particularly at the invasive tumor margins. While elevated viscosity is thought to impede migration, paradoxically, GBM cells often exhibit enhanced invasiveness following exposure to such environments. Here, we present a novel open microfluidic platform that enables real-time, high-resolution analysis of GBM cell behavior under tunable viscosity conditions, free from the geometric confinement of traditional closed systems. Using the U-251 cell line and primary GBM-3 cells, we demonstrate that acute exposure to high-viscosity medium (7.1 cP) suppresses migration, but prolonged exposure induces a primed, pro-invasive state. This phenotype is driven by cytoskeletal remodeling, shortened focal adhesions, nuclear translocation of YAP, and transcriptional upregulation of mitochondrial energy metabolism. Microfluidic chemotaxis assays reveal that while viscosity gradients do not guide migration (i.e., no visco-taxis), preconditioned cells exhibit enhanced chemotactic invasion toward nutrient cues. These findings establish extracellular viscosity not as a migratory attractant but as a mechanical conditioning factor that modulates cellular phenotype and invasion potential. Our open microfluidic platform provides a powerful framework to dissect the mechanobiology of GBM and other solid tumors.