Label‐Free Cell Migration Assay Using Magnetic Exclusion

In vitro wound healing assays are widely used to investigate cell migration during various physiologic and pathologic processes. However, traditional scratch‐based assays produce cell‐free areas that are not reproducible, whereas the alternate insert‐based exclusion method is expensive and time‐consuming. Here, a rapid, label‐free, insert‐free magnetic exclusion technique, where magnetic fields are used to create cell‐free areas is described. Suspensions of diamagnetic cells in a paramagnetic culture medium are seeded into microwells placed on an array of the coaxially arranged ring and cylinder magnets. In the presence of an inhomogeneous field, the magnetic susceptibility difference drives the cells toward an annular region of the lowest field strength. Annular cell aggregates of reproducible dimensions are produced on tissue culture‐treated and collagen I‐fibronectin coated surfaces within 3 h. The effects of the paramagnetic agent on cell viability, metabolism, and gene expression are investigated. A mathematical model reveals the dynamics of the cell‐free area closure. The magnetic exclusion technique is inexpensive, easy to use, and amenable to automation. Potential applications include cancer research, high throughput drug discovery, and screening. A magnetic exclusion‐based cell migration assay is reported. Cells suspended in the paramagnetic culture medium are magnetically manipulated to form annular aggregates within 3 h. No significant changes in cell viability, metabolism, and transcriptional profiles are observed due to the paramagnetic agent exposure. The cell‐free area closures under different epidermal growth factor concentrations are analyzed using a mathematical model.