If they can be loaded with different functional molecules at the same time, these nanoparticles could:
a. carry an anti-cancer drug and
b. bind specifically to cancer cells to release the drug locally.
This is the principle of nanoparticle-based drug targeting, which, however, has never been successfully applied to cancers in humans.
Now, first clinical trials with such an anti-cancer nanoparticle compound (after previous positive results in mice and monkeys) have been concluded and may be good news for mankind: in many cases, the nano-drug actually stopped the growth or even reduced the tumors.