Credit: © 2008 Wiley

The formation of new capillaries from existing blood vessels — a process known as angiogenesis — is important in many biological processes including embryonic development and tumour growth. Molecules known as cytokines drive this process and have been used to repair damaged blood vessels after a heart attack. Researchers in the US and Israel have now discovered that inorganic nanoparticles have pro-angiogenic properties1 that are similar to cytokines and could possibly, therefore, be developed into treatment strategies.

The team, led by Debabrata Mukhopadhyay from the Mayo Clinic in Rochester, found that europium (III) hydroxide nanorods could promote the growth of endothelial cells (those that line the walls of blood vessels) and, for a range of dosages, also activate an important signalling pathway for angiogenesis. Other lanthanide hydroxides, such as neodymium and terbium hydroxide, did not have any effect.

Using a well-known angiogenic assay based on membranes obtained from chick embryos, the nanorods were seen to promote the formation of blood capillaries comparable to those induced by cytokines. Further experiments revealed that the nanorods may be involved in the production of reactive oxygen species, which are important in angiogenesis, although the detailed mechanism of the effect remains a mystery.