Intellectual Merits: While cell migration on 2-dimensional (2-D) substrates has been studied for many decades, the physical challenges cells face when moving in 3-D environments are only beginning to emerge now. The central hypothesis of this proposal is that deformation of the large and stiff nucleus presents a rate-limiting step during migration through tight constriction encountered in 3-D environments such as extracellular matrixes or during intra- or extravasation. This project will address to what extent the deformability of the nucleus governs the transit of cells through narrow constrictions by monitoring cells as they migrate through microfluidic channels with defined constrictions while visualizing subcellular deformations and transit efficiency. In addition, ablation of cytoskeletal filaments with femtosecond laser pulses as cells pass through narrow constrictions will be used to determine whether the nucleus is being pulled or pushed by the cytoskeleton to overcome its resistance when squeezing through constrictions smaller than the size of the nucleus. Complementing these experiments, molecular sensors engineered from modified nuclear envelope proteins that report tensile forces and localized compression at the nuclear envelope by changes in fluorescence intensity or fluorescence resonance energy transfer (FRET) efficiency will be applied to cells during 3-D migration to quantify the cytoskeletal forces acting on the nucleus during 3-D migration and visualize their distribution along the nuclear periphery.
Broader Impact: The research activities will be complemented with a comprehensive education and outreach program that builds on simplified models of the proposed research to introduce middle and high school students to biomedical engineering, with the goal of increasing participation of female students in science, technology, engineering, and math (STEM) subjects. Tapioca pearls, the key ingredient of the popular bubble tea, will be used as safe, easily accessible, and inexpensive stand-in for biological cells, while simple 'millifluidic' devices replace technically demanding microfluidics designs to probe cellular biomechanics. These 'tapioca millifluidics' experiments, along with accompanying lectures, will be introduced to students from underserved middle and high schools as part of existing and novel outreach programs at Cornell University that target high school girls and underrepresented minorities to provide them with hands-on experiences in biomedical engineering to boost confidence, meet role models, and overcome gender stereotypes. An additional education component is the creation of an online portal for self-directed learning to address the challenge of teaching interdisciplinary biomedical engineering courses to students with diverse academic backgrounds.
