A new strategy to manipulate cell operations is demonstrated, based on membrane-receptor-specific interactions between colloidal peptide-capped gold nanoparticles and human umbilical vein endothelial cells. It is shown that colloidal gold nanoparticles of similar charge and size but capped with different peptide sequences can deliberately trigger specific cell functions related to the important biological process of blood vessel growth known as angiogenesis. Specific binding of the peptide-capped particles to two endothelial-expressed receptors (VEGFR-1, NRP-1), which control angiogenesis, is achieved. The cellular fate of the functional nanoparticles is imaged and the influence of the different peptide-coated nanoparticles on the gene expression profile of hypoxia-related and angiogenic genes is monitored. The findings open up new avenues towards the deliberate biological control of cellular functions using strategically designed nanoparticles.