Microfluidic-based wound healing assays for investigating the effects of matrix viscoelasticity on tumor cell migration†

Tumor cell migration plays a significant role in the processes of local invasion and distant metastasis, closely related to the high mortality rate of malignancies. The mechanical properties of the extracellular matrix can regulate tumor cell behaviors. However, classical methods for studying cell migration mostly use stiffer (≥MPa level) materials to mimic the physical microenvironments, neglecting the viscoelasticity of soft physiological tissues containing a dynamic interstitial fluid microenvironment. In this paper, a versatile microfluidic device integrated with a hydrogel for wound healing assays is proposed to investigate the effects of matrix viscoelasticity on tumor cell migration. A long, narrow cell-free area with a width of 500 μm is created to simulate a wound at the bottom of the chamber by adjusting the pressure imposed on the upper layer of the device. The flow fields in the chambers are evaluated by numerical simulation and particle tracking assays. Viscoelastic and elastic hydrogels with similar compressive moduli (∼2 kPa) are used to mimic the mechanical microenvironments. HeLa cells are cultured in hydrogel extracts to assess their cytotoxicity. For wound healing assays, hydrogels are perfused into the chambers of the device and cover the cell monolayer and cell-free area. The higher closure of the wound exposed to the viscoelastic hydrogel indicates that hydrogel viscoelasticity can promote tumor cell migration. The wound healing assays also show a dose-dependent response to doxorubicin hydrochloride treatment. All results demonstrate that the proposed microfluidic strategy provides a prospective platform for in vitro cell research and anti-cancer drug screening.