Density Based Characterization of Mechanical Cues on Cancer Cells Using Magnetic Levitation.

Extracellular matrix (ECM) stiffness is correlated to malignancy and invasiveness of cancer cells. Although the mechanism of change is unclear, mechanical signals from the ECM may affect physical properties of cells such as their density profile. The current methods, such as Percoll density-gradient centrifugation, are unable to detect minute density differences. A magnetic levitation device is developed (i.e., MagDense platform) where cells are levitated in a magnetic gradient allowing them to equilibrate to a levitation height that corresponds to their unique cellular density. In application of this system, MDA-MB-231 breast and A549 lung cancer cells are cultured and overall differences in cell density are observed in response to increasing collagen fiber density. Overall, density values are significantly more spread out for MDA-MB-231 cells extracted from the 1.44 mg mL(-1) collagen gels compared to those from 0.72 mg mL(-1) collagen, whereas no significant difference with A549 cell lines is observed. The MagDense platform can determine differences in cellular densities under various microenvironmental conditions. The imaging of cancer cells in a magnetic levitation device serves as a unique tool to observe changes in phenotypic properties of cancer cells as they relate to micromechanical cues encoded by the ECM.