Lichtgedanken 05

S C HW E R P U N K T 15 05 | LICHT GEDANKEN F E AT U R E Dye-marked nanoparticles flourescing under ultraviolet light. Chemists Prof. Dr Schacher (p. 14, on the left) and Felix Wendler (on the right) use ultraviolet irradiation to cause the nanoparticles releasing the substances encapsulated within. The chemists want to develop the concept, so that the particles would react to radiation from the visible and infrared spectrum and medicines could be administered more accurate. meaning that it is released at a specific time and location. Jena’s chemists use small, molecules sensitive to light which are stimulated by light at a specific wa- velength resulting in the active substan- ce being released. Fluorescent dye as a test substance Doctoral candidate Felix Wendler has produced light-responsive nanopar- ticles made from so-called terpolymers for this purpose as part of his doctoral thesis in Schacher’s team. These po- lymers consist of three distinct com- ponents called monomers that orga- nize themselves into nanostructures of a defined size in aqueous solution. Wendler has used light-sensitive pho- toacids as a building block for the syn- thesis of these polymers. In addition, the fluorescent dye »Nile red« has been encapsulated into the particles. »In this experiment, the dye acts both as test substance, and as a probe«, explains the young chemist Wendler. A specific fluorescent signal can be detected whe- reas the dye remains within the poly- mer assembly or package. If the vessel is then irradiated with UV light, the photoacid molecules integrated within the particle become stimulated and ch- ange the local pH value. »As a result, the particles disperse and the dye escapes into the surrounding solution which can be tracked directly by measuring the change in the fluore- scence signal«, says Wendler. Although the photoacids have been proven to be efficient »light switches« for nanopar-