[link to www.sciencemag.org]

"Oncologists have long known that in rare cases, after patients receive radiation therapy to shrink a tumor, the immune system will mount an aggressive response that wipes out not only the tumor, but metastases throughout the body that hadn’t been treated with the radiation.Researchers now think that irradiation sometimes kills tumor cells in a manner that exposes new antigens to T cells, priming them to target other tumor cells that carry them as well.
...
Lin wanted to see whether he could use nontoxic nanoparticles to sensitize the immune system in a similar way."

(less than 50%)

While it all sounds like good news, as someone who studies nanostructures such as nanoparticles, I find the claim "nontoxic nanoparticles" rather a wild and worrying claim.

Nanotoxicity is not really understood these days. Elements that are inert and non-toxic in macro-, meso- and microscale (e.g. gold or titanium oxide) can exhibit extreme toxicity towards living cells when delivered in nanoscale.

The electronic structure of materials determines their chemical response towards the environment (and vice versa). Due to the small size of nanoparticles, they do not have the same well-understood electronic structure as, let's say, microscopic quantities of the same element.

In physics we say that the instead of having an electronic band structure, the particles exhibit discrete electronic states much like molecules. In the complex environment of the human body, it is near-impossible to predict how such an electronic structure interacts with the living cells and tissue.

Furthermore, nanoparticles have a very high surface/bulk atom ratio. That is, surface properties largerly determine the properties of nanoparticles whereas in bulk (e.g. microscopic amounts) materials the surface effects are less important. This is important, because surface atoms are less coordinated (i.e. they have fewer neighbouring atoms) and less tightly bound to the particle. The local electronic structure is different on surfaces and that, in turn, determines the reactivity of the particle. Once again, it's near impossible to predict what these reactive properties are in living tissue.

Interestingly, these nanoscale effects are likely to be responsible for the anti-bacterial effects of colloidal silver.