Abstract

Cancer is a complex disease that originates from various mutations in cells, influencing cellular growth and proliferation. During cancer progression, the biophysical properties of cells, as well as their responses to surrounding mechanical stimuli, are altered. These alterations impact their interactions and communications with their microenvironment and enhance the motility of cancer cells, allowing them to detach from the primary tumor and invade other healthy tissues/organs. Progress in nanotechnology and nanoscience has resulted in the nano-bio-interaction field in which the interaction between nanoparticles and cells are studied to develop innovative nanomedicines to optimize and revolutionize classical methods for cancer treatment and management. While nanomedicines could directly and selectively target cancer cells and deliver anti-cancer reagents to cancer cells, their presence into cells (even without drugs) could cause significant changes in the mechanobiological properties of cells. Although many studies showed that nano-bio-interaction could induce cytoskeletal changes in cancer cells, it is not yet clearly known or understood how these changes could potentially influence cancer progression.
This dissertation focused on how cell-nanoparticle interactions and the resulting mechanobiological change in cancer cells would influence their cellular functions. Here, we utilized three different types of gold particles with different physicochemical properties to study their interactions with both healthy and cancer cells. In the first step of this research, we employed various nanotechnology and microscopic techniques including fluorescent imaging, SEM, Raman spectroscopy, dark-field imaging and hyperspectral imaging to study the behavior of gold nanoparticles in cells in terms of cellular uptake, cytotoxicity, internalization level, and subcellular localization. The findings revealed that all types of particles, sphere-shaped, star-shaped, and Swarna Bhasma, are non-toxic to the cells even with increasing doses and exposure times. Raman enhancement results highlighted the importance of nano-morphology in mediating changes in the affinity of gold nanoparticles to different chemical structures in cells, which is essential for developing nanomedicines. The hyperspectral technique was then utilized to detect particles in different regions of cells with measuring the intracellular plasmonic responses of nanoparticles. It was found that the regional-dependent plasmonic shifts of gold nanoparticles could be used to estimate the subcellular localization of nanoparticles. Nanospheres showed higher accumulation in cells, and they exhibited a greater plasmonic shift with more sensitivity to their neighboring medium compared to Swarna Bhasma and nanostars.
This dissertation then used Atomic Force Microscopy for mechanobiological measurements and to study their alterations upon incubation with gold nanoparticles. Imaging techniques confirmed morphological and cytoskeletal changes in cancer cells after uptake of gold nanoparticles. Migration assays revealed that nanospheres cause stronger changes than nanostars in the dynamic capability of cancer cells, by significantly slowing down their migration. In support of this, biomechanical measurements showed that internalized gold nanospheres reduce the elasticity of cancer cells by 66% more compared to nanostars. The same trend was also observed in the adhesion levels of treated cells. We observed that nanospheres are mainly distributed in regions where force is generated and translocated for cell migration, and their distribution reasons why their impacts are stronger than nanostars. Furthermore, our simulations showed that the bulk stiffness of cells has contradictory effects on cell deformation and overcoming forces at the cell-substrate interfaces required for cell migration. To approximate the migratory capability of cells, we defined a stiffness-dependent energy term, migratory index, to uniquely capture the effects of both phenomena. Our modeling revealed that there is an optimal stiffness value/range associated with maximal migration, and when bulk stiffness deviates from the optimal range, the rate of migration is predicted to decrease. Our experimental results showed that nanospheres could change the bulk stiffness of cancer cells outside of the optimal range for efficient migration, and we hypothesize that this could suppress their metastatic potential of cancer cells.