Lichtgedanken 05

S C HW E R P U N K T 22 It is Tuesday morning. Two young men don their white coats and enter a lar- ge, brightly lit room: neon tubes bathe their workplace in white light. The air conditioning quietly hums and silen- ces all other noises that may pass th- rough the broad window from outside. No one says anything. The two men are happy with this set-up; the work processes are part of the routine. Whi- le one places a box of brown chicken eggs on the table, the other has already taken his place and is opening a pocket knife. He carefully lays it on the table in front of him, with the sharp side of the blade facing upwards. Then, without looking up, he takes one of the eggs, hits it against the table with a swift hand movement, slowly opens the egg and carefully pours the yolk and egg white into a small glass dish. Finally, he places a glass lid on top, moves the receptacle to one side and reaches for the next egg. The two men get through around 500 chicken eggs a month; so- metimes more, sometimes less. Yet Martin Rabel and Paul Warn- cke—as the scientists are called—do not work in a bakery or in a large kit- chen; instead they are completing their doctorate at the Institute of Pharmacy at the University of Jena. They are in- vestigating nanoparticles and explo- ring how they interact with tissue and blood, and how they behave within an organism. The tiny materials are beco- ming increasingly important in the de- velopment of new medicines. They can be used to transport active substances to specific targets within the body whe- re they are needed (see interview on page 25). Nanoparticles are also found in contrast agents used in diagnostics. However, before they can be used, it must be proven that they will not harm the organism. But how do these small particles behave in the body? Can they even move within the body? And what happens when the particles disinteg- rate into their components? Scientists have to answer all of these questions by conducting extensive tests on each individual material in order to find the ideal particle for each application. Initially, the scientists check the safety of nanoparticles using two-dimensi- onal cell cultures. They place the par- ticles on these cultures and observe over several days whether or not the cells die. »This process doesn’t tell us how the nanomaterial behaves in a natural environment, what happens when the particles are flushed past a cell, interact with components of the blood, and whether they damage blood vessels or easily flow through them«, explains Warncke. The delicate blood vessels in the egg can be used as a test system In order to take a closer look at these processes, Jena scientists are turning to fertilized chicken eggs. »General- ly speaking, the eggs that we receive are one day old«, says Martin Rabel. »We then store them in an incubator for three days, open them and look to see if they have developed normally. We then return them to the consistent- ly warm environment for a further 24 hours.« The compact incubator is right next to their workstation. It looks like a vault; but, instead of gold, it is the egg yolk that shines on the stacked glasses. You can see that a blood vessel system is already developing within the eggs with the naked eye: the bright yellow yolk is covered with fine blood vessels. A small red node can be seen in the centre of this network: this is pumping the blood through the vascular system and will develop into the chicken he- art. Even at this early stage, it ensures there is a constant blood flow. And this is exactly what the two scientists need for their work, so that they can find out how nanoparticles behave within a vascular system. But how do the tiny particles get into the fine blood vessels within the egg? Paul Warncke has re- trieved a four-day-old egg from the in-