Lichtgedanken 05

S C HW E R P U N K T 19 05 | LICHT GEDANKEN What would an ideal nanoparticle for use as a medicine carrier actually look like? The particles need to be able to enclose as much of the active substance as possible. Their surface should be functionalized so that the content arrives precisely where it is needed and that is also where the substance must be released from the nanoparticles. The remaining parts of the particles must also be biocompatible—in other words, harmless for the organism. That is quite a big ask. It gets even more complicated: the chemical diversity of the active substances that need to be transported into the orga- nism by nanoparticle is great and thus the polymers that make up the particles need to be just as varied. Why? The only way to safely »package« medicines and administer them in high concentrations is for the active substance and the polymer to fit together perfectly in terms of their chemical properties and structure. In other words, you need to find perfect chemical matches? Exactly. And I can find these using a process of »trial and er- ror«. I can take an experimental approach to find out which polymer goes with which active substance. But this is not a very efficient way to do it. And that is why you recommend taking a different approach? Yes. Chemical syntheses often take a very long time, especially when you are dealing with new types of polymers. A doctoral candidate may spend around a year »cooking« a specific type of polymer. And if you then discover that the result doesn’t fit with the active substance as required, you have wasted a lot of time without achieving any tangible results. By simulating the formation of nanoparticles on a computer, we can signifi- cantly accelerate and systematize the procedure. What are the defining criteria for »matching« the medicine and the polymer? Our goal is to achieve the maximum absorption capacity for the active substance and the maximum efficiency for its release from the polymer particles. We use our simulations to predict these properties for certain polymers. We want to systematically vary the polymer structure and calculate the compatibility with selected active substances—and to do all of this within the computer model. On the basis of a poly- mer-based structure from polyketones and polyesteramides, we will simulate the effects of chemical modifications to this basic structure on the absorption capacity for specific active substances. More specifically, this concerns changes in the hydrophobicity of the polymers; in other words, their beha- viour compared to solvents such as water. Which substances are we talking about? On the one hand we work with model substances, such as dyes, to test and optimize our procedures. On the other hand, we also use real active substances, which are being investi- gated in other sub-projects of the »PolyTarget« collaborative research centre. For example, we want to find matching po- lymers for the substance »Ex527«. This substance is currently being investigated as a possible drug for the treatment of neu- rodegenerative diseases. How do your findings end up being used in real-life scenarios? We have been working with a large team of synthesis chemis- ts from the very beginning. As such, we are able to verify the results of our simulations directly through experiments. Af- ter all, we will only reach our goal if simulation and synthesis can work together hand-in-hand.  F E AT U R E Prof. Dr Marek Sierka (left) and doctoral candi- date Andreas Erlebach’s »laboratory« is actually a PC—supplemented with an arsenal of main- frame computers, which are housed in a server room in the Jentower.