Lichtgedanken 03

S C HW E R P U N K T 28 now touches on the similarities between the microscopes used by biologists and physicists. It appears that they cannot be easily compared in the case in question. Together, we swap lab coats for jackets and set off, arriving just a few minutes later in a physics lab of the Abbe Center of Photonics. Microfluidics gives information on composition of blood samples Now equipped with shoe covers, I exa- mine a microscope. Under the lens is a chip stamped with fine, winding lines. Susanne Pfeifenbring, who works here most of the time, explains to me what this is all about. This chip measuring about one by one-and-a-half centime- tres forms the foundation of drop-based microfluidics. Physicist Pfeifenbring, who is doing her doctorate at the Leibniz Institute of Photonic Technology (IPHT) within the framework of BLOODi, re- sponds to my puzzled look by explai- ning further: »We place a drop of blood on the chip and examine the blood cells using non-linear oscillation spec- troscopy.« Little the wiser, I study the chip, but Pfeifenbring continues: »Every cell consists of various macromolecules, such as proteins, lipids and DNA. If we irradiate the whole blood with two la- ser pulses, we selectively cause different molecules to oscillate and observe their distribution in the cells. As the oscillati- on spectrum of the cell is as specific as a fingerprint, we can use it to identify the biochemical composition. This is how we find the neutrophils in whole blood, for example.« This is important, because in the physics lab, too, researchers aim to have as little impact as possible on the blood samples and, unlike in the flow cytometry proce- dure commonly used to date, they do not want to mark cells. Using oscillation spectroscopy, also called Raman spec- troscopy, they could determine in this way which cells are involved and, ideal- ly, whether they have been in contact with particular pathogens. »Combi- ning non-linear laser spectroscopy with microfluidics in order to examine whole blood is completely uncharted territo- ry,« adds Susanne Pfeifenbring. As we slowly make our way back out- side, Marc Thilo Figge once again high- lights the key feature of BLOODi: »Here, physicists develop new optical methods for which they on their own do not see any necessity. And our biologists know what they want to study and what they want to find, but they are not able to create the necessary methods.« The clo- se cooperation between laser physicists, biologists and immunologists thus sti- mulates fruitful research ideas and the possibility of making them a reality th- rough the collaboration between the va- rious disciplines. Time-lapse microscopy makes diffe- rences visible And because someone is also needed to analyse and interpret results from the laboratory, scientists such as Prof. Fig- ge himself and doctoral candidate Ivan Belyaev complete the team. At the Cen- ter for Systems Biology of Infection at the HKI, which we visit last, the experi- ments are mathematically analysed. For example, they receive data from Ales- sandra Marolda and take a closer look at the development of neutrophils in the individual »snapshots«. The sequences of images produced using the time-lap- se microscope—also called Live Cell Imaging—enable researchers to deter- mine dynamic characteristics of the cell shapes. »This allows us to capture diagnostic criteria for cells under health Prof. Dr Thilo Figge (left) and doctoral candidate Ivan Belyaev analysing experimental data. Here they take a closer look at images of granulocytes produced by time-lapse microscopy. F E AT U R E