Separating the Living from the Dead: An Electrophoretic\nApproach

Cell viability studies are essential\nin numerous applications,\nincluding drug development, clinical analysis, bioanalytical assessments,\nfood safety, and environmental monitoring. Microfluidic electrokinetic\n(EK) devices have been proven to be effective platforms to discriminate\nmicroorganisms by their viability status. Two decades ago, live and\ndead <i>Escherichia coli</i> (<i>E</i>. <i>coli</i>) cells were trapped at distinct locations in an insulator-based\nEK (iEK) device with cylindrical insulating posts. At that time, the\ndiscrimination between live and dead cells was attributed to dielectrophoretic\neffects. This study presents the continuous separation between the\nlive and dead <i>E</i>. <i>coli</i> cells, which\nwas achieved primarily by combining linear and nonlinear electrophoretic\neffects in an iEK device. First, live and dead <i>E</i>. <i>coli</i> cells were characterized in terms of their electrophoretic\nmigration, and then the properties of both live and dead <i>E</i>. <i>coli</i> cells were input into a mathematical model\nbuilt using COMSOL <i>Multiphysics</i> software to identify\nappropriate voltages for performing an iEK separation in a T-cross\niEK channel. Subsequently, live and dead cells were successfully separated\nexperimentally in the form of an electropherogram, achieving a separation\nresolution of 1.87. This study demonstrated that linear and nonlinear\nelectrophoresis phenomena are responsible for the discrimination between\nlive and dead cells under DC electric fields in iEK devices. Continuous\nelectrophoretic assessments, such as the one presented here, can be\nused to discriminate between distinct types of microorganisms including\nlive and dead cell assessments.