Probing the functional mechanism of cell-to-cell interaction and cell migration with optical tweezer-based cell manipulation tool

Abstract

Cell-to-cell interaction and cell migration play crucial roles in a variety of physiological and pathological processes. However, the understanding of individual cell mechanisms at a fundamental and integrated level remains elusive thus far. Current methods for studying cell-to-cell interaction and cell migration are mainly based on batches of cells, which are prone to the loss of heterogeneity and spatiotemporal information. Methods that can specifically and accurately control cell interaction and migration at the single-cell level are lacking. In this thesis, a cell manipulation system, which integrates robotics, optical tweezers, and nanotechnology, is developed to allow the functional mechanisms of cell-to-cell interactions and cell migration to be tested and probed. This thesis is performed in the following three perspectives. First, a new approach that combines optical tweezers and fluorescence microscopy technology is proposed to manipulate cell adhesion for cell-to-cell interaction study. Optical tweezers are used in trapping single cells to identify the adhesion states between two types of cells. Fluorescence intensity is used as a label to study the activation of the signaling pathway of single cells and to further explore cell-to-cell interaction. The feasibility and correctness of this new approach is demonstrated through a case study on interactions between leukemia cancer and bone marrow stromal cells. The combined use of optical tweezers and fluorescence microscopy technologies is proved to provide a new opportunity to detect spatiotemporal information in cell-to-cell interaction. Second, with the optical tweezer-based cell manipulation system, a study on the characterization and control of receptor–ligand-mediated cell adhesion is carried out to probe the mechanism of cell-to-cell interaction. The cell-to-cell interaction is regulated through drug treatment and control of cell adhesion contact. A specific drug is used to inhibit receptor–ligand binding, and the adhesion contact is controlled by assembling leukemia cells at different positions of stromal cell layers. The findings that the distribution and amount of adhesion molecules can largely affect cell adhesion are obtained. Third, the cell migration mechanism is investigated by utilizing the cell manipulation system. Specially designed beads, which are loaded with chemoattractant, are robotically controlled by optical tweezers to induce cell migration in vitro. The platform can flexibly create chemical gradient to mimic an in vivo environment for probing cell chemotaxis mechanisms. A unique method that can quantitatively measure the cell protrusion force during cell migration is developed based on the platform. In summary, the proposed optical tweezer-based cell manipulation tool provides novel solutions for the study of cell-to-cell interaction and cell migration with micro/nanoscale-level precision. Studying the adhesion between leukemia cancer and bone marrow stromal cells provides insights into the functional mechanism of cell-to-cell interaction. The study of leukemia cell migration in an artificial chemical environment reveals the magnitude of protrusion force that drives a cell to move toward a stimulus. This thesis will lay a solid foundation for the further exploration of the regulation mechanism of cell-to-cell interaction and the new targeted therapies in nanomedicine.

Date of Award	3 Oct 2014
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Dong SUN (Supervisor)