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Investigation of cell environment interaction in vitro using a femtosecond laser

Abstract

The interaction between cells and their extracellular environment regulates diverse cell behavior such as migration, proliferation, and differentiation. At the tissue level, the cell-environment interaction determines the structure and organization of tissues and organs. Therefore, understanding of the cell-environment interaction provides the fundamental knowledge for the development of tissue engineering, biotechnology, and pharmaceutical research. Comparing to in vivo investigation of cell-environment interaction, in vitro study has attracted more interest because it allows users to analyze a specific parameter independently in a controlled system. Two approaches have been followed by researchers to study cell-environment interactions. One approach is from the outside-in perspective, by tuning an environmental cue independently. The other approach is from the inside-out perspective, by probing and manipulating the cells. Much research progress has been made from both perspectives. However, the development of this area is still largely impeded by the inadequate capability to recapitulate the intricacy found in three- dimensional in vivo environment and to study a single cell. To provide fundamental insight into this field, new fabrication and manipulation tools must be developed to overcome those obstacles. A femtosecond laser, which has the capability to fabricate three-dimensional nanoscale structures and the ability to ablate a submicron hole in the cell membrane, is a promising candidate to further facilitate the research in this field. In this thesis, we used a femtosecond laser to tune the Poisson's ratio of the underlying substrate of cells, a fundamental property of materials. For the first time, suspended web structures exhibiting negative and positive Poisson's ratio were developed and the cell behavior on the web structures was analyzed. We also standardized the protocol for the femtosecond laser-assisted optoporation, which is widely used in the delivery of exogenous materials into cell interior to manipulate cellular activities. In addition, we combined the femtosecond laser fabrication with nanoimprinting to significantly increase the fabrication output for two-dimensional nanoscale structures

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