(315b) Single-Walled Carbon Nanotube Dynamics As a Physical Sensor for Cellular Health

The intracellular environments of cells are tightly regulated with homeostatic control over viscosity, pH, and biomolecular concentrations. Novel sensors are required to determine these properties in live cell and real-time applications, where dysregulation of the parameters can be indicative of various types of disease. Single-walled carbon nanotube (SWCNT)-based sensors are one promising option due to their photostable fluorescence emission in the near-infrared region. We hypothesize that SWCNT particle tracking can be used as a viscosity biosensor inside live cells to identify disease states.

To explore our hypothesis, we conducted experiments in two phases. First, we measured SWCNT dynamics in polymer solutions as model solutions with controlled properties to gain insight into how the dynamics of highly anisotropic nanoparticles (i.e. SWCNTs) couple to the structure and viscoelasticity of complex fluids. Particle tracking analysis showed large deviations in diffusivity for SWCNTs in solutions of high molecular weight PEO, with SWCNTs diffusing up to 300 times faster than expected from the Stokes-Einstein expression. Second, we translated this finding into live MCF10a breast epithelial cells, whereby DNA-functionalized SWCNTs are actively internalized into the cells and remain vesicle bound in the endosomal pathway. Using sucrose as an osmolytic agent, we shocked the cells and used SWCNT particle tracking to report real-time variations in intracellular viscosity. Our results demonstrate that SWCNT dynamics can directly quantify cytoplasmic viscosity and provide insight into cellular health.