Gene dispensers.

Researchers have developed a new means for transferring genes to treat diseases. The gene therapy method relies on a nanoscale architecture with many alternating layers of polyester and DNA. Once this material is inside the body, water degrades the polyester layer by layer, for a slow, controlled release of genetic material to nearby tissues.

The technology has shown preliminary success in transferring genes both to isolated cells grown in the lab and blood vessels in rabbits, reports David M. Lynn of the University of Wisconsin-Madison.

Key to the new system are novel, water-soluble polyesters that carry a net positive charge across their surfaces. Thin films of the material make ideal platforms for negatively charged DNA molecules.

The multilayered-film strategy could be useful in arterial stents, says Lynn. Surgeons mechanically unclog arteries and then use the tiny mesh tubes to prop open the vessels. Because arteries fitted with stents can begin reclogging shortly after surgery, researchers have been looking to coat the tubes--or a sleeve inserted inside them (SN: 3/18/06, p. 163)--with clog-inhibiting genes (SN: 11/24/01, p. 328).

Lynn's layer-cake approach offers more flexibility than earlier systems did because different genes can be incorporated into different layers, and the polyester's recipe can be customized, layer by layer, for different breakdown rates.

Although the material's longest gene-release period thus far has been 3 months, Lynn says that the system could be designed to shed genes for a year. Moreover, he notes, the layers could coat injectable particles that could carry DNA to a target tissue via the bloodstream. He predicts that none of these new systems will be ready for human trials for at least a decade.