The performance and biological fate of nanoparticles deployed in a medical context is strongly dependent on surface properties. We are developing novel surface modification strategies for use in controlling biointerfacial phenomena related to therapeutic and diagnostic nanoparticles. In one project, we are using polydopamine coatings as primers to functionalize gold nanorods with antibodies for cancer treatment (Figure). Conjugation of antibodies and passivating polymers to the nanorod surface via polydopamine was employed for targeting nanorods to cancer cell surfaces. Once bound to cells, the near-IR absorbance of the nanorod was used to induce photothermal ablation of cells. Another example is given by spherical gold nanoparticles which were functionalized with heparin for in-vivo CT imaging (Figure).