Pluronic Triblock Copolymer Encapsulated Gold Nanorods as Biocompatible Localized Plasmon Resonance-Enhanced Scattering Probes for Dark-Field Imaging of Cancer Cells

Gold nanorods (GNR) are synthesized using cetylmethylammonium bromide (CTAB) surfactants which function as structure-directing agents. However, CTAB forms a tightly bound cationic bilayer on GNR surface with the cationic trimethylammonium head group exposed to the aqueous media, which is known to be highly toxic in vitro and in vivo. Pluronic is a non-ionic triblock polymer, which can associate with CTAB and form stable CTAB–polymer complexes due to hydrophobic interactions. In this work, two types of Pluronic triblock copolymers were used to encapsulate GNR to reduce their cytotoxicity and improve colloidal and optical stability for biological applications. These formulations were characterized by UV–vis absorption spectra analysis, transmission electron microscopy, cell viability studies, differential interference contrast microscopy and dark-field imaging.