(633d) Gold Nanoparticle-Bovine Serum Albumin Complexes for Imaging and Analysis of Macromolecule Drug Delivery through Murine Endothelial Monolayers

Gold nanoparticles (GNP) have been widely used for bioimaging and biomedical sciences because of their unique optical and electronic properties related to their sizes and shapes. Here, we focus on the use of a gold-BSA complex as an imaging-contrast agent to understand the effect of size and surface properties on the pathways of particle transport through a monolayer of mouse endothelial cells.

Transport from the blood into the surrounding tissues has direct implications for understanding healthy metabolic function, disease states involving transmigration of certain classes of viruses, inflammatory cells, and metastatic cancer cells, and tissue delivery of drugs. Transport across the endothelial barrier occurs by two main pathways ? the paracellular pathway through the intercellular junctions and the transcellular pathway through endothelial cells mediated by transcytosis via caveolae. We have prepared gold-BSA complexes by Flash NanoPrecipitation (FNP) to directly image and elucidate the hypothesized mechanisms of junctional and vesicular transport across the endothelial barrier. BSA has been used to convert the hydrophobic GNP suspension to a hydrophilic suspension. The hydrodynamic diameter of the gold-BSA complexes varied from 5 nm to 50 nm for various ratios of GNP and BSA from 1:10 to 50:1. The sizes and structures of the gold-BSA complexes were measured by dynamic light scattering (DLS) and confirmed by transmission electron microscopy (TEM).

Compared to hydrophilic polymers, albumin was chosen because it is effectively internalized via caveolae in endothelial cells. However, when conjugated with gold NPs, most proteins including BSA undergo conformational changes at the binding boundary with GNP, which may or may not result in the loss of biological activity. Confirmation that BSA retained its native conformation was conducted using UV-Vis, fluorescence, and circular dichroism (CD) spectroscopy and nuclear magnetic resonance (NMR).