Lichtgedanken 05

S C HW E R P U N K T 26 not enough. We need models that allow us to simulate the behaviour of nano- materials, even after they have been al- tered by the body through the so-called protein shell, or flow in the blood ves- sels. We don’t necessarily need to use animal testing for this. What can we use instead? We have developed a chicken egg mo- del, which gives us an insight into the blood vessel system and allows us to directly observe the behaviour and the effect of nanoparticles (see reportage on p. 20 ff). Thus, we can answer lots of questions that classic cell cultures do not cover and we can significantly reduce the number of tests on animals required. What are the possible side effects of nanomaterials? It depends on the kind of materials and particles, what they are degraded for and how long they remain in contact with the body. There are nanoparticles, which are made from biocompatible and biodegradable polymers. They are degraded in the body after a short pe- riod and their components are metabo- lized. These are expected to be harm- less. But there are also particles made of metals or metal compounds, which are used as a contrast agent in various diagnostic procedures, for example. These can remain in the body for seve- ral months and can, in some situations, be toxic or may cause immune respon- ses. How can these side effects be avoided? This is another of the »PolyTarget« fields of research. One method that we already know about is to make the sur- face of the particles »invisible« to the immune system. Water-soluble mole- cules, such as polyethylene glycol, are anchored to the surface. If these par- ticles reach the bloodstream, the orga- nism can no longer »see« the particles and thus, immune responses are inhi- hited. Just like stealth aircraft, which are invisible to radar, these particles are called »stealth« particles. Where do you see the greatest poten- tial for the use of nanoparticles in medicine? In the treatment of cancer and infec- tions. This is because the blood vessel barrier on tumour cells and inflamed tissue cells is changed. To put it simply, they have holes in them. In the case of tumour tissues, these holes can be so large that they can function as entry points for nanoparticles. Intact tissue, i.e. without holes, cannot uptake the particles. Active substances, such as highly potent chemotherapeutic agents, only act in the tumour tissue without side effects in the healthy tissue.  Sample tubes containing nanoparticles. F E AT U R E