University of Michigan physician and researcher James Baker has developed multipurpose nanoparticles precisely engineered to slip past barriers such as blood vessel walls, latch onto cancer cells, and trick the cells into engulfing them as if they were food. These Trojan particles flag the cells with a fluorescent dye and simultaneously destroy them with a drug.

The heart of Baker’s approach is a highly branched molecule called a dendrimer. Each dendrimer has more than a hundred molecular “hooks” on its surface. To five or six of these, Baker connects folic-acid molecules. Because folic acid is a vitamin, most cells in the body have proteins on their surfaces that bind to it. But many cancer cells have significantly more of these receptors than normal cells. Baker links an anticancer drug to other branches of the dendrimer; when cancer cells ingest the folic acid, they consume the deadly drugs as well.

Japanese researchers have created hollow “nanocages” of proteins that can hold a few molecules of a drug (or a gene, for use in gene therapy) and bring them straight to the liver.

The scientists, who report on their work in the journal Nature Biotechnology, used a protein from the hepatitis B virus. When this protein is created in large amounts, it forms cagelike structures of about 110 molecules each, with a diameter of about 80 nanometers.

Using small electric pulses, wthey put genetic material or proteins inside these cages. Their surface holds a peptide that binds with a receptor on human liver cells.

The researchers suggest that with alterations in the surface peptide, the cages could be used as vehicles to deliver drugs or genes to other tissues as well.