Microfluidic Electroporative Flow Cytometry for Studying Single-Cell Biomechanics

Biomechanical properties of cells yield important information on the disease state of cells such as transformation and metastasis. Screening of cells based on their biomechanical properties provides rapid tools for label-free diagnosis and staging of cancers. However, existent single cell techniques for measuring biomechanical properties suffer from low throughput (<1 cell/min). This prevents the application of these assays to a large cell population which produces information with statistical significance. In this study, we applied microfluidics-based electroporative flow cytometry (EFC) that combined electroporation with flow cytometry to study deformability of cells at the single cell level with a throughput of ~5 cells/s. The cell swelling during flow-through electroporation was recorded in real time. We believe that the degree of such swelling was indicative of the cell deformability and the cytoskeleton mechanics. Three cell types (MCF-10A, MCF-7 and 12-O-tetradecanoylphorbol-13-acetate (TPA) treated MCF-7) with different malignancy and metastatic potential were tested using our approach. We found that the more malignant and metastatic cell types exhibited more swelling due to higher cell deformability. Furthermore, the disruption of microtubules by colchicine caused substantial change in the EFC results, which confirmed that EFC data strongly reflected the cytoskeletal mechanics. Finally, the cell type with the highest metastatic potential also suffered the most cell death due to the flow-through electroporation treatment, presumably due to the most substantial cell swelling which could irreversibly rupture the membrane. EFC provides a new method for examining single cell biomechanics with high throughput. We believe that this technique will be useful for mechanistic studies of cytoskeleton dynamics and clinical applications such as diagnosis and staging of cancers in general.