(674a) Diffusing Colloidal Probes of Cancer Cells

To engineer nanoparticles for novel biosensing, diagnostic imaging, and drug delivery applications, the interactions of nanoparticles with the surface of cells must be characterized to better understand their influence on specific and non-specific cell surface adhesion, internalization pathways, and toxicity. In order to develop models to aid in optimization and design in these systems, direct measurements of colloidal interactions with cell surfaces are required that are both quantitative and sensitive to determine the impact of particle composition and surface chemistry. In this talk, we report the use of diffusing colloidal probes to directly measure cell surface interactions with kT-scale sensitivity with newly developed imaging and analysis techniques. Dark field video microscopy allows for label-free imaging of colloidal particles and live cells. With combined real-time particle tracking and cell boundary determination, particle trajectories can be monitored in relation to their distance from the cell surface which allows for direct measurement of equilibrium and non-equilibrium colloid-cell interactions. Using this technique, polyethylene glycol (PEG), bovine serum albumin (BSA), and dextran, hyaluronic acid (HA) functionalized colloidal silica were used to measure specific and non-specific macromolecular interactions with the surface of epithelial breast cancer cells. Ultimately, our results demonstrate how diffusing colloidal probe microscopy can be used to characterize biomolecular and biophysical properties of cell surfaces.