Abstract
Disease can induce changes to subcellular components, altering cell phenotype and leading to measurable bulk-material mechanical properties. The mechanical phenotyping of single cells therefore offers many potential diagnostic applications. Cells are viscoelastic and their response to an applied stress is highly dependent on the magnitude and timescale of the actuation. Microfluidics can be used to measure cell deformability over a wide range of flow conditions, operating two distinct flow regimes (shear and inertial) which can expose subtle mechanical properties arising from subcellular components. Here, we investigate the deformability of three colorectal cancer (CRC) cell lines using a range of flow conditions. These cell lines offer a model for CRC metastatic progression; SW480 derived from primary adenocarcinoma, HT29 from a more advanced primary tumor and SW620 from lymph-node metastasis. HL60 (leukemia cells) were also studied as a model circulatory cell, offering a non-epithelial comparison. We demonstrate that microfluidic induced flow deformation can be used to robustly detect mechanical changes associated with CRC progression. We also show that single-cell multivariate analysis, utilising deformation and relaxation dynamics, offers potential to distinguish these different cell types. These results point to the benefit of multiparameter determination for improving detection and accuracy of disease stage diagnosis.
Highlights
Disease can induce changes to the biological constitutents of cells, such as the cytoskeleton, leading to changes in whole cell-deformability[1]
atomic force microscopy (AFM) studies have previously shown a reduction in the elastic modulus of a metastatic colorectal cancer (CRC) cell line (SW620) compared to one deriving from a primary tumour (SW480), showing that phenotyptic softening occurs with metastatic progression due to changes in the actin cytoskeleton[37,38]
There is a systematic increase in deformation value (DI/A) for SW620 compared to SW480 indicating that under shear dominant conditions the SW620 are significantly more deformable than the SW480 cells
Summary
Disease can induce changes to the biological constitutents of cells, such as the cytoskeleton, leading to changes in whole cell-deformability[1]. The different approaches perform deformation over a range of lengthscales (from whole cell to local measurments), timescales and magnitudes of force, subjecting the cells to either tensile, compressive or shear forces The combination of these factors has resulted in a wide-range of mechanical properties being reported in the literature[12,17]. By using high-Reynolds numbers (Re ≫ 1), FC was ~1000 times greater than FS resulting in an inertia-dominant flow regime[18] In this regime, increased deformability was found following lymphocyte activation and in stem cell pluripotency, i.e. cell states that are characterised by loose, open, chromatin structures[23]. Results showed that a shear-dominant and low-strain regime was most sensitive to cells becoming softer when treated with the actin destabilizing drug latrunculin A, comparatively the inertia-dominant and high strain regime could not detect any changes. These results offer further insight into metastasis due to being performed across a different range of timescales and forces, as well as being performed on a single cell suspension as opposed to cells adhered to a surface
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