Releasing therapeutic compounds from polymer-coated stents is not new, but materials designed specifically to control the timing of DNA release are novel and hold promise for gene-based therapies. Chemical engineers at the University of Wisconsin, Madison, are developing multilayered polyelectrolyte films to tune the timing of DNA release from cardiovascular stents and additionally promote delivery of therapeutic genes into cells (Biomacromolecules, DOI: 10.1021/bm0604808). "This work sets the foundation to control the timing and sequence of release of two or more types of DNA or other therapeutics, which has been extraordinarily difficult to achieve by conventional methods," notes lead researcher David M. Lynn. The trick is laying down a dozen alternating 10-nm layers of DNA and a cationic polyamine (shown), which degrades by ester hydrolysis. The polymer was designed to interact electrostatically with polyanionic DNA, which means less polymer is required on the stent. The interaction also helps promote cellular uptake because the DNA is disguised by the polymer.