Versatile dielectrophoresis based microfluidic platforms for chemical stimulation of cells
Creators: name: Tang, Shiyang
Publisher: name: RMIT University
Year: 2024

description: The purpose of this project is to develop versatile microfluidic systems, which take advantage of dielectrophoresis, for the rapid creation of customized cell clusters, chemical stimulation of the patterned cells under well-controlled environmental conditions, and analysis of cellular responses using different microscopic techniques.<br><br>As the first contribution, the author shows that the reorientation of the microfluidic channel with respect to the microelectrodes can be utilized to alter the characteristics of the dielectrophoretic (DEP) system. This enables the author to change the location and density of immobilized viable cells across the channel, release viable cells along customized numbers of streams within the channel, and improve the sorting of viable and nonviable cells in terms of flow throughput and efficiency of the system.<br><br>As the second contribution, the author presents a novel approach to change the DEP response of nonviable yeast cells by chemically altering their surface properties. The author’s studies show that treating nonviable yeast cells with low concentrations of ionic surfactants can significantly change their surface properties, making them exhibit a strong positive DEP response, even at high medium conductivities. The capability of this treatment is demonstrated in two proof-of-concept experiments to create isolated or adjacent clusters of viable and nonviable cells next to each other.<br><br>As the third contribution, the author utilizes dielectrophoresis for studying the dynamic response of cells following chemical stimulation. The DEP system enables separation of the budding yeasts from a background of non-budding cells, and their subsequent immobilization onto the microelectrodes at desired densities. The immobilized yeasts are then stimulated with Lyticase to remove the cell wall and convert them into spheroplasts in a dynamic process, which depends on the concentration of Lyticase.<br><br>As the fourth contribution, the author introduces a novel method for immobilization of the cell organelles released from the lysed cells by patterning multi-walled carbon nanotubes (MWCNTs) between the microelectrodes. A strong electric field can be induced at the free ends of MWCNT chains, which is utilized to immobilize the released cell organelles from budding yeast cells after treating them with high concentration of Lyticase.<br><br>As the fifth contribution, the author develops a DEP-based microfluidic platform for interfacing non-adherent cells with high-resolution scanning electron microscopy (SEM). The developed DEP system enables rapid immobilization, on-chip chemical stimulation and fixation, and dehydration of samples without deposition of chemical residues over the cell surface. These advantages are demonstrated for comparing the morphological changes of non-budding and budding yeast cells following Lyticase treatment.<br><br>In summary, the research conducted by the PhD candidate enables studying of the dynamic cell responses under various chemical treatments using versatile DEP based microfluidic platforms. The PhD candidate also believes that the presented research will offer practical solutions for future biomedical micro-devices.