Lin Shi

Date of Graduation

2017

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Chemical and Biomedical Engineering

Committee Chair

Yong Yang

Committee Co-Chair

Robin Hissam

Committee Member

Yuxin Liu

Committee Member

Karen Martin

Committee Member

Charter Stinespring

Abstract

In most living tissue, cells resident in a complex microenvironment where these cells interact with the extracellular matrix (ECM) and the neighboring cells. The interactions between cells and ECM could regulate the cell behavior. Similar to in vivo, in vitro models have been reported that cells have the ability to sense the nanotopography and stiffness of synthetic substrate and, the variation of substrate nanotopography configuration and stiffness could affect cell phenotype and function.;The first project focused on applying nanotopography to capture circulating tumor cells (CTCs) for early cancer detection. CTCs shed from primary tumors, transport through the bloodstream to distant sites, and cause 90% of cancer deaths. Although different techniques have been developed to isolate CTCs for cancer detection, diagnosis and treatment, the heterogeneity of expression of the target antigen and the significant size variance in CTCs limit clinical applications of antibody- and size-based isolation techniques. Cell adhesion using nanotopography has been suggested as a promising approach to isolate CTCs independent of surface marker expression or size of CTCs. However, the influence of nanotopography configuration (geometry and dimensions) on CTC capture efficiency has not been investigated. This study examined capture performance of several cancer cell lines of different types, surface marker expression and metastatic status on nanotopographies of various geometry and dimensions without antibody conjugation. Compared with flat surfaces and isotropic, discrete nanopillars, anisotropic nanogratings favored cancer cell adhesion, thus improving the capture efficiency. This study provides useful information to optimize nanotopography to further enhance CTC capture efficiency.;The second project focused on understanding the effects of substrate stiffness on fibrogenic responses of human lung fibroblasts to engineered nanomaterials. Most existing in vitro models focused on conducting the experiment using the rigid tissue culture polystyrene (TCPS) surfaces, which were much stiffer than the actual in vivo cell microenvironment. Thus, the behavior and nanomaterial responsiveness of cells could be largely changed due to the deviation of substrate stiffness when cultured on TCPS. Therefore, it is of the critical need to create physiologically relevant tissue models to mimic the in vivo environment by introducing stiffness cue. This study used the synthesized polyacrylamide (PAAm) hydrogel to represent the normal and fibrotic conditions of lung tissues to conduct in vitro models. The fibrogenic responses and mechanosensing of fibroblasts to carbon nanotubes (CNTs) at different stiffness conditions have been explored. This study provides understanding of the regulatory pathways and mediators of fibrogenic activities, which will potentially help identify therapeutic targets against fibrosis.;The incorporation of substrate nanotopography and stiffness could be further applied in three-dimensional culture model as the difference in dimensionality could also substantially change the cell behavior and function. Cells under in vivo conditions are embedded in multiple ECM components and experiencing different biophysical stimuli compared to those cultured on top of the two-dimensional substrate. Moreover, by introducing flow and shear stress into the in vivo system could largely replicate the in vivo condition, like the ultimate organ-on-a-chip microfluidic device. This study provides insight on building physiologically relevant in vitro model for disease detection and modeling and could be future applied in drug development and disease treatment.

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