Lichtgedanken 05

S C HW E R P U N K T 23 05 | LICHT GEDANKEN Image left (from the left): Doctoral candidate Martin Rabel, Prof. Dr Dagmar Fischer and doctoral candidate Paul Warncke investigate the long-term effects of nanoparticles as part of the project »Biological elimination of complex diagnostic nanoparticles« (NanoBEL). They are using the blood vessels in ferti- lized chicken eggs as model tissue. Image right: Martin Rabel examines the chicken eggs, which are a few days old and stored in an incubator. cubator and placed it on a microscope. He places the filled petri dish on the slide. A bright light illuminates it from below. Martin Rabel brings a small box containing rows of ampoules. They have coloured lids for ease of identifi- cation and come with adhesive labels. They contain the nanoparticles. The liquids within the small plastic cont- ainers are either light or dark brown. »We are mainly investigating different iron oxide particles and they are gene- rally dark brown«, says Rabel. Deep blue flows through red veins, surrounded by bright yellow The liquid containing the particles can be easily gathered into a syringe with a microinjector on the front. The small device has a needle at the tip. As it is very hard to distinguish the brown of the nanoparticles from the red blood with the naked eye, the two early-career scientists have opted for a methylene blue solution for today for demonstration purposes. Warncke looks through the eyepiece of the microscope whilst holding the injector in his right hand like a pen. He slowly approaches the egg with the needle, pierces the yolk and injects two microlitres of the blue liquid directly into the vein leading to the heart. This operation on the open egg is re- miniscent of vascular surgery. »It is not easy to hit the vein precisely wi- thout piercing right through it«, says Warncke. The speed and accuracy suggest that he has done this experi- ment many times before. Gradually the blue spreads from the injection site through the entire network of veins. If the brown particle solution had been used instead; millions of nanopar- ticles would now be flowing through the veins. The two researchers use the microscope to closely observe how they behave—initially at hourly inter- vals and then at daily intervals. They also take regular photographs of their findings. They can record around ten particle types each week using this procedure. The investigations are so extensive, because one particle generally compri- ses a core and a covering layer. They each have different primary materials. The core is surrounded by a polymer that protects it, makes it easier to trans- port it through the body and increases biocompatibility. Together, the two components form a nanosystem with specific properties, which differ from those of the two substances if they were separated. And, even though they are introduced into the body together, they could then disintegrate; either accidentally during transportation th- rough the body, or once the particle has reached its destination and degraded. In addition, as the nanoparticle comes into contact with body fluids, proteins and other organic components are de- posited on the nanoparticle and form a so-called biomolecule corona, which lends the nanoparticle an entirely new biological identity and can affect the toxicity of nanoparticles, their interac- tion with cells and their distribution within the body. In an ideal scenario, these changes would improve the im- pact of the nanoparticle; but often they also destroy it. In any case, this variety of possibilities equates to a lot of work in the laboratory for the scientists. While Warncke injects nanoparticles into the egg, Rabel places another egg into the petri dish beside him. He is interested in the surface of the egg. He holds a pair of tweezers in his right hand, which he uses to pick up a small black ring of plastic, which he then calmly places on the yolk. He then uses a pipette to drop a little of the blue liquid into the tiny pool. The circular boundary means that none of the liquid can spill over the surfa- ce—as such, the nanoparticles remain localized. F E AT U R E