Researchers at the University of Illinois at Urbana-Champaign in the US have created a set of gold nanorods with electrostatically trapped rhodamine 6G molecules on their surfaces. These molecules were used as model “drugs”. Successive layers of charged polymers – negatively charged poly (acrylic acid, sodium salt) and positively charged poly (allylamine hydrochloride)  were wrapped around the nanorods so that polymers alter the surface charge of the rods and help trap the rhodamine 6G molecules.
It was found that the number of molecules  released from the rods can be related to the number of polymer layers wrapped around the rods and that the number of molecules released could be tuned 100-fold. This makes them promising as drug-delivery vehicles because of small size and easy functionalization of these structures.
Gold nanorods can easily be made to absorb near-infrared laser irradiation of the electromagnetic spectrum to trigger drug release. The heat generated due to absorption of near-infrared light can be used to locally destroy cancer cells. The finding isusefull for light-initiated drug-delivery applications as the release of the drug could be controlled by carefully choosing the number of polymer wrapping layers.