Varying etching conditions influences the angles formed by the panels in these nanoboxes. The left column is a close-up of the tin hinge material. The other columns show the boxes at different magnifications. The panels are patterned with the letters "JHU" with line-widths of 15 nanometers. Credit: ACS/Nano Letters

Chemists have become very skilled at building 2-D nanostructures, but making 3-D patterned structures for drug delivery, electronics and other applications has proved more challenging. In particular, no one has been able to make 3-D structures with patterned surfaces.

David Gracias and Jeong-Hyun Cho of Johns Hopkins University in Baltimore have overcome this problem. They first made arrays of patterned, cross-shaped nickel structures on a silicon wafer, then added tin hinges. When placed in a plasma etching chamber, the flat structures folded up into cubes and released from the wafer. To make nanocubes as small as 100 nanometers a side, the researchers added another panel.

The work is described online in the journal Nano Letters, where the researchers write that it should apply to other polyhedral shapes as well.

Researchers may have made some incorrect assumptions about how to design nanoparticles deliver drugs that target tumor cells, according to preliminary research presented this week at the 2009 Materials Research Society Spring Meeting in San Francisco.

Most of the nanoparticle "envelopes" used to encapsulate cancer drugs rely on two mechanisms to get to their destination. The drugs are coated in these envelopes so that they cannot pass through healthy blood vessels into healthy tissues but can pass through the holes in leaky blood vessels that feed tumors. But this is no guarantee that the tumors will take up the drug, which might continue circulating in the blood. To make the targeting more specific, the outside of these envelopes are often decorated with molecules that are recognized by receptors present in large numbers on the surfaces of tumor cells. Chemists usually load the nanoparticles with these tumor-specific molecules, according MIT chemical engineering professor Paula Hammond, whom I caught up with at the conference. "The assumption is, if you increase the [number of places to bind], you increase the drug uptake," she says.

But Hammond presented preliminary results suggesting that the number of targeting molecules isn't the only important factor in getting a tumor to take up a drug; their arrangement is also important. Hammond compared drug uptake when the targeting molecules were loaded all over the nanoparticle envelope, and when they were clustered in patches, as they are on biological cells. "We found that we can greatly influence how much tumors take up by changing the size of the patches, and that drug uptake goes down if there are too many patches."

Yesterday, the U.S. Food and Drug Administration (FDA) announced the creation of a nanotechnology initiative in collaboration with the eight Texas academic institutions that make up the Houston-based Alliance for NanoHealth. (These include Rice University, the University of Texas, and the M.D. Anderson Cancer Center.)

So far, not many details have been released. The FDA's announcement describes the initiative's goal as "to help speed development of safe and effective medical products." The statement also emphasizes the need to "expand knowledge of how nanoparticles behave . . . and to facilitate the development of tests and processes that might mitigate the risks associated with nanoengineered products."

This is good news for environmental and consumer groups concerned that research on the potential toxicity of nanomaterials hasn't been keeping pace with research on their applications.

There are certainly large gaps in our knowledge about these materials, and filling them in will be no small task. The Environmental Protection Agency (EPA) has taken the stance that nanostructured materials shouldn't be regulated differently from conventional materials with the same chemical structure. But of course size matters in nanotech--that's the reason people are excited about its applications to begin with, and assuming that toxicity isn't affected by these materials' size and shape doesn't make sense. The diversity in size, shape, and composition of nanomaterials makes it impossible to make blanket statements about their safety. Hopefully, the FDA program will help make sense of these complex questions.

Information gathered under the FDA program, according to the statement, will be in the public domain. Let's hope this promise is one with more teeth in it than the EPA's. Much of the information submitted to that agency's voluntary nanomaterials program has been classed as "confidential business information" and is not available to the public.