Fig. 1.

Computer model of a 30-nm-diameter gold nanoparticle coated with alkanethiol molecules. Nanoparticle gold atoms are shown as yellow spheres, alkyl chain carbon atoms are shown as blue sticks and terminal, and surface-exposed sites are shown as grey spheres. The red background represents the biological environment. The introduction of therapeutic drug molecules (by, e.g., ligand exchange and/or regioselective surface patterning) is depicted by the clusters of molecules terminating in white, orange, and pink spheres to represent different functional groups (D. Thompson, unpublished data)