Lichtgedanken 05

S C HW E R P U N K T 14 Nanoparticles with a light switch Researchers working with Prof. Dr Felix Schacher and Prof. Dr Benjamin Dietzek are developing nanopar- ticles that release encapsulated active substances »on demand«. In an initial proof-of-concept study, the chemists showed that it is possible to control the release of a model substance encapsulated within the nanoparticle using ultraviolet rays. Currently, the concept is about to be adjusted in to order to apply it to biologocial systems, for instance, in medicine. BY UTE SCHÖNFELDER Nanoparticles with a built-in light switch—this is one way of describing the concept that the team of chemis- ts, led by Felix Schacher and Benjamin Dietzek, want to realize as part of the collaborative research centre »PolyTar- get«. The researchers are developing photosensitive nanoparticles which can be triggered through exposure to light at specific wavelengths to release their content »at the touch of a button«. »One of the great benefits of this type of nanoparticles is that we can control their size, shape as well as functionality, and can load it with desired substances«, says Schacher. As a result, this can pre- vent active substances from reacting in the wrong parts of the organism—and causing unwanted side effects. »On the other hand, the packaging means that significantly larger amounts of active substances can be administered as they are transported to the desired location in high concentrations rather than in dissolved form.« However, this benefit can only be reali- zed if the package containing the acti- ve substance can be released precisely where they should take effect. There are various strategies to achieve this. The simplest one is the package simply dis- solving after a certain period or at a spe- cific pH value, e.g. in the stomach, and thus releasing its content. »Applying this method, you can only control the time span, the effect, however, often re- mains non-specific and can thus cause side effects«, explains Schacher. A far more promising method is to integra- te a mechanism into the particle which allows the release of the encapsulated substance to be controlled externally