Cell adhesion

Electrical impedance of cells is a sensitive indicator of changes in cellular structure and biophysical characteristics. Integration of electrical impedance sensing in microfluidics can be a useful tool for characterization of blood cells for their disease state, such as sickle cell disease and malaria. The first part of this dissertation presents application of a microfluidics-based electrical impedance sensor for the study of sickle cell disease. Dynamic cell sickling-unsickling process of blood cells in response to cyclic hypoxia was measured. Strong correlation was found between the electrical impedance data and patients’ hematological parameters such as levels of sickle hemoglobin and fetal hemoglobin. In addition, application of electrical impedance spectroscopy in narrow microfluidic channel was used for label-free flow cytometry and non-invasive assay of single sickle cells under controlled oxygen level. We demonstrate the capability of this new technique in differentiating normal red blood cells from sickle cells, as well as sickled cells from unsickled cells, using normoxic and hypoxic conditions. The second part of this dissertation reports an application of electrical impedance sensing for the study of placental malaria. Testing conditions were optimized so that electrical impedance can be used for real time monitoring of different cellular and molecular level variations in this in vitro model of placental malaria. Impedance characteristics of cell proliferation, syncytial fusion and long-term response of BeWo cells to adhesion of infected erythrocytes were obtained and related to the immunostaining results and inflammatory cytokines measurements. Comparing to the conventional optical microscope-based methods, electrical impedance sensing technique can provide a label-free, real-time monitoring tool to study erythrocytes and cytoadhesion, and can further be extended to other disease models and cell types.

Soluble form of Junctional adhesion molecule C (sJAM-C) has been identified to cause angiogenesis as well as chemotaxis in endothelial cells. However, the role of sJAM-C in the context of cancer has not been elucidated. Our atomic force microscopy (AFM) stiffness measurements of normal mammary epithelial cells (MCF 10A) have shown a two-fold decrease in cell's stiffness in response to sJAM-C. Changes in cell stiffness are indicative of modulations in a cell's mechanical properties. Our results indicated that sJAM-C increased the MCF 10A cell migration about two-fold and also promoted a three-fold increase in chemotaxis. Additionally, sJAM-C treatment resulted in considerable filamentous-actin loss and peripheral actin ring breakage. We also found activation of Rho signaling pathway to be the main mechanism behind sJAM-C mediated alterations in MCF 10A cell cytoskeleton and motility. Our data present for the first time that sJAM-C is a pro metastatic mediator for normal mammary epithelial cells.