(179r) Swcnts Transport Faster Than Expected in Polymer Solutions

Particle tracking offers powerful insights into nanoparticle dynamics within complex environments. Single-walled carbon nanotubes (SWCNTs), owing to their intrinsic fluorescence in the near-infrared region and high aspect ratio, have become useful tools for studying local physical and chemical conditions. In this study, we leverage the particle tracking of SWCNTs to explore their transport behavior in viscoelastic media as a foundation for developing physical biosensors capable of detecting intracellular changes indicative of disease.

To test our hypothesis, we conducted a series of experiments aimed at understanding the coupling between the dynamics of SWCNTs and the structure and viscoelasticity of complex fluids. We prepared solutions of polyethylene oxide (PEO) with varying molecular weights at concentrations of 1, 3, 5, 10, 20, and 30 c*, where c* denotes the overlap concentration of polymer chains. Surfactant-functionalized SWCNTs were introduced into these solutions and imaged using near-infrared (NIR) fluorescence microscopy. To identify the effects of anisotropy, we compared these measurements to similar experiments performed using spherical nanoparticles with diameters of roughly 200 nm, similar to the hydrodynamic diameter of SWCNTs. We find significant deviations in the diffusivity of SWCNTs in high molecular weight PEO solutions, with SWCNTs diffusing up to 300 times faster than predicted by the Stokes-Einstein equation. By contrast, spherical nanoparticles exhibited diffusivities consistent with SE predictions across all molecular weights. This anomalous transport behavior of SWCNTs, which we hypothesize is caused by their anisotropic shape and their ability to rapidly navigate through the polymer mesh, indicates that SWCNTs exhibit a high sensitivity to variations in solution viscosity. Ongoing investigations aim to identify the specific factors influencing their motion to develop a predictive model. Upon establishing the correlation between SWCNT dynamics and medium properties, we will proceed to investigate how changes in these properties within the cellular environment affect SWCNT motion.