To achieve external control, Lin is using iron-oxide nanoparticle caps which can be manipulated by a magnetic field. In a simple demonstration of the principle, Lin holds a refrigerator magnet up to a liquid-filled glass vial containing human cervical cancer cells grown in vitro that contain nanospheres capped with iron-oxide particles. The cells slowly migrate and cluster to the side of the vial next to the magnet.
"By using a powerful magnet, we can first concentrate the nanospheres at a particular point, such as a tumor site, and then use the magnetic field to remove the caps and release the drug," Lin said. "The advantage of using a magnetic trigger as opposed to a ultraviolet light trigger is that there's no limit to the depth of tissue we are able to probe ?think of an MRI."
Beyond the possibilities for intercellular drug delivery, the nanospheres may provide the key to studying what takes place within a cell. Currently, scientists have difficulty introducing chemicals or genes into cells without either damaging the cell or causing a chain-reaction of events that can't be tracked.
"With current gene therapy, it's possible to switch genes on and off, but you don't really know if you are affecting other parts and processes of the cell as well," Lin said. "You may be able to get a plant cell to produce a certain desired product, but the yield may drop significantly."
By using externally controlled nanospheres, Lin explains that it may be possible to sequentially release genes, chemical markers and other materials within cells in order to track