| In addition to the well-established influence that soluble factors have on cellular behavior, physical forces are also now known to play a large role. Many cellular processes such as proliferation, apoptosis, differentiation, and mobility, have all been shown to be influenced by mechanical inputs. This has been demonstrated in developing embryos, and also during cancer progression, from tumor growth and invasion, to metastasis. Tools which enable the measurement of mechanical forces in a variety of systems in vitro and in vivo can enable a deeper understanding of the mechanical inputs that cells are receiving in 3D tissues, and enable quantification of stress patterns in these systems. My work encompasses the generation of droplets with well-controlled properties, used as force transducers to measure stresses within 3D, multicellular systems. By characterizing the interfacial tension, and by imaging the shape of droplets in 3D, anisotropic stresses can be measured. Precise control of the interfacial tension, droplet size, and cell-droplet interaction enables their use to accurately measure anisotropic stresses applied both in and in vitro. Using these droplets, I quantify spatiotemporal stresses within growing mesenchymal cell aggregates, in 3D.;First I describe a new surfactant system which allows for precise control over the interfacial tension of fluorocarbon oil droplets, while still mediating the interactions between droplets and surrounding cells. This surfactant system is resistant to changes in interfacial tension in complex chemical environments, with varying ionic strength and small molecules competing for the surface. These droplets are generated with devices and materials that are commercially available, making the technique openly accessible to most laboratories. Studies aimed at measuring mechanical stresses in a variety of systems either in vivo or in vitro, at different length scales (by controlling the droplet size), may make use of this method.;I then use these droplets to measure endogenous, anisotropic stresses within model tissues - 3D cellular spheroids. These experiments enable a spatiotemporal map of stresses to be generated from growing, 3D spheroids of mesenchymal cells. Stresses are quantified for both mediated adhesion, and hindered adhesion, between droplets and cells. This allowed the investigation of stress contributions from both tensile and compressive stresses (in the first case), and those solely due to compressive stresses (in the second case).;Lastly, I further enhance fluorocarbon oil-in-water emulsions in a collaborative project which includes the synthesis and characterization of new fluorosurfactants. In contrast to previously established methods, these fluorosurfactants are generated from completely non-ionic starting materials, enabling their use in biological applications which may contain molecules (e.g proteins) susceptible to be influenced by charged surfactants. The new fluorosurfactants offer excellent long-term stabilization of fluorocarbon oil-in-water emulsions, without the need for additional co-surfactants. |
