Study for cell positioning and cell-to-cell interactions with robot-tweezer manipulation system

Abstract

Transportation and positioning of biological cells has become increasingly important in contemporary biomedical research. A significant demand for both accuracy and productivity in cell positioning highlights the need for automated cell transportation with integrated robotics and micro/nano manipulation technologies. Most of the existing methods for studying cell-to-cell interactions are based on a large number of cells and a sufficient quantity of analytes, which unfortunately lose heterogenous information of individual cells. Techniques which can be used to study cell-to-cell adhesive interaction at the single-cell level are needed. In this study, a robot-tweezer manipulation system for automatically positioning biological cells is investigated, which enables further research on cell-to-cell interactions between leukemia cells and bone marrow stromal cells. This thesis study includes the following three aspects. First, a new approach is proposed to incorporating robotics technologies into optical tweezers for automated transportation of biological cells. A robot-tweezer manipulation system is proposed. Dynamics of the cells in optical trapping is analyzed. Cell motion in the x-y plane is mainly governed by the trapping force of the optical trap and viscous drag force of the liquid. After discussion of these two forces, theoretically, the dynamics of the trapped cell is reduced to a constrained first-order system. A control algorithm for single-cell positioning is developed with micro/nano precision, which enables the robot-tweezer system to position biological cells rapidly and precisely. Second, a synchronization controller is developed by utilizing the cross-coupling approach, which can be used to address the multi-cell transportation problem. Synchronous transportation of multiple cells while maintaining their original pattern is necessary in a variety of bioapplications, such as steady transportation of large arrays of cells for simultaneous cellular assays in parallel, undisturbed positioning of cell body" connected with cell-to-cell channels, movement of artificial biological tissues fabricated with multiple cells, and so on. The basic idea of the proposed control research is that multiple cells track each desired trajectory individually while synchronizing motions amongst each other to maintain the required multi-cell pattern. Simulation and experiments performed on transporting yeast cells and T cells while maintaining their required shape patterns demonstrate the effectiveness of the proposed approach. Third, the robot-tweezer manipulation system is used to study the cell-to-cell adhesive interactions. Elucidation of the mechanism of leukemia cell adhesion to stroma and the adhesion mediated interactions contributing to leukemia initiation and progression may provide a promising new paradigm for development of specific targeted therapies. Cell-to-cell adhesive interactions between leukemia cells and bone marrow stromal cells are studied using the proposed approach. To demonstrate the feasibility of this approach, the viability of leukemia cells after optical trapping is tested and verified. Adhesion properties of leukemia cells on bone stromal cells are then characterized. Adhesion ability of leukemia cells on stromal cells is reduced by As2O3 and AMD3100 or by heparin, which preliminarily demonstrate the specificity and mechanism of the adhesion. In summary, the proposed robot-tweezer manipulation system and enabled closedloop control technology provide a novel solution for positioning single/multiple cells rapidly and precisely, which exhibits much biological relevance in cell-to-cell interaction, drug discovery and tissue engineering. The study of leukemia-stromal adhesive interactions provides insight into understanding interactions between leukemia and stromal cells, which helps further with providing specific targets for therapeutic intervention.

Date of Award	3 Oct 2011
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Dong SUN (Supervisor)