Date of Award

1-1-2014

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School/Department

Department of Nanoscale Science and Engineering

Program

Nanoscale Engineering

Content Description

1 online resource (xii, 117 pages) : color illustrations.

Dissertation/Thesis Chair

James Castracane

Committee Members

Hassaram Bakhru, Lauren Brasile, Scott Tenenbaum, Janet Paluh

Keywords

BioMEMS, Chemotaxis, Implantable device, Metastasis, Microfabrication, Tumor Microenvironment, Cancer, Nanomedicine

Subject Categories

Nanoscience and Nanotechnology

Abstract

In the past decade, it has become increasingly recognized that interactions between cancer cells and the tumor microenvironment (TME) regulate metastasis. One such interaction is the paracrine loop between macrophages and cancer cells which drives metastatic invasion in mammary tumors. Tumor associated macrophages release epidermal growth factor (EGF), a chemoattractant which induces the migration of cancer cells toward the blood vessels. The cancer cells reciprocate by releasing a macrophage chemoattractant, colony-stimulating factor 1 (CSF-1), resulting in the co-migration of both cell types and subsequent intravasation. In this work, a new technology has been developed for studying the mechanisms by which invasive tumor cells migrate in vivo toward gradients of EGF. Conventional in vitro methods used for studying tumor cell migration lack the complexity found in the TME and are therefore of limited relevance to in vivo metastasis. The Nano Intravital Device (NANIVID) has been designed as an implantable tool to manipulate the TME through the generation of soluble factor gradients. The NANIVID consists of two etched glass substrates, loaded with a hydrogel containing EGF, and sealed together using a polymer membrane. When implanted in vivo, the hydrogel will swell and release the entrapped EGF, forming a diffusion gradient in the tumor over many hours. The NANIVID design has been optimized for use with multiphoton-based intravital imaging, to monitor migration toward the device at single-cell resolution. Stabilization techniques have been developed to minimize imaging artifacts caused by breathing and specimen movement over the course of the experiment. The NANIVID has been validated in vivo using a mouse model of metastasis. When implanted in MDA-MB-231 xenograft tumors grown in SCID mice, chemotaxis of tumor cells was induced by the EGF gradient generated by the device. Cell motility parameters including velocity, directionality, and chemotactic index were calculated by tracking the migrating cells. Many additional chemicals and proteins are compatible with the NANIVID, providing a platform to initiate controlled changes in the TME that were not possible using conventional methods. Additionally, a one-dimensional (1D) cell migration assay was developed using electrospun nanofibers to mimic the collagen fibers associated with invasive breast tumors. Collagen fibers provide a substrate for cancer cells to migrate upon in vivo, serving as a connection to the blood vessels, to promote metastasis. Development of the migration assay enabled a low cost, versatile platform as a model system for the investigation of the motility processes used by tumor cells while constrained to 1D.

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