Angewandte Chemie International Edition
© WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Angewandte Chemie International Edition 2006, 45, 4612–4617
Microcapsules enter cells and an external flash of light triggers release of their contents
Pharmacologists dream of being able to deliver a drug directly to its target location within a cell. This would make it possible to avoid many of the undesired side effects of medications. The dosage could also be reduced and adjusted more precisely to the needs of the diseased cell. Microcapsules are one possible tool for such a strategy; the cavities of these single- or multilayer spheres of suitable polymers can be filled with drugs for delivery. Then the microcapsules need only be introduced into cells and their contents released in a controlled fashion.
One way this might work has been examined by the research groups of André Skirtach in Potsdam and Wolfgang Parak in Munich. They prepared multilayer microcapsules with a diameter of about 4.5 µm. If these microcapsules are heated in the presence of a fluorescence dye, they absorb it. At the same time, the capsules become stronger and more stable and shrink to about 3 µm.
The researchers incorporated silver and gold nanoparticles into the shells of the capsules. These act as absorption centers for light so that a laser pulse can be used to break apart the capsules and release their contents.
In the next step, the cells must be taken up by living cells. This is fairly simple to accomplish by incubating a cell culture with the capsules over several hours. The authors used a tumor cell line for this. Careful selection of the external conditions ensures each cell takes up only one capsule. When a laser pulse is then beamed at the cells from the outside, the capsules release their fluorescent contents into the interior of the cells.
Unincorporated capsules that remain outside of the cells do not interfere; they remain unaffected and intact.