Animals have been used for centuries as unwilling subjects to study the toxicity of chemical compounds. You don’t have to be a member of PETA to wish for better alternatives, and there’s already been substantial progress toward reduced use of animal models. Researchers at the Fraunhofer Institute for Cell Therapy and Immunology in Potsdam, Germany working with biologists at Hebrew University of Jerusalem have created a microfluidic bioreactor that is able to keep alive liver cells while studying how they react to different drugs and other substances.
The device keeps the cells viable for weeks and provides a look at how they’re doing in real time during the entire experiment. This is a major advancement over being able to sample cells at the end of an experiment. This is done by using sensors inside the bioreactor that measure the amount of oxygen consumed by the cells living inside. This is an indicator of the rate of metabolic activity taking place inside the cells, and the rate is often very indicative of the type of metabolism taking place. So while it’s an indirect assessment, it provides a very important window on what’s going on inside a liver cell when a toxin or other compound is introduced.
Some details about how the technology was created according to Fraunhofer:
One of the tasks of Duschl’s team was to design a suitable reactor vessel containing numerous microfluidic channels, in collaboration with their partners in Israel. One of the main challenges was to ensure that all cells were equally supplied with the growth medium, so they are evenly distributed and do not form clumps. But this fine distribution was a source of other problems, for the wider the distance between the cells, the weaker the signals captured by the sensors. “What we needed was a sensor technology capable of dealing with a high concentration of cells, without the risk of interference effects that would falsify the test results.” The IZI project team came up with the idea of using tiny polymer particles containing a luminescent dye. This dye emits a phosphorescent glow when exposed to a monochromatic LED light source, which excites individual electrons and raises them to a higher energy level. The electrons return to their original energy level within a fraction of a second, and the remaining energy is emitted in the form of phosphorescent light. The time required by the electrons to lower their energy level is directly related to the concentration of oxygen in the surrounding air. “In other words, the time this takes indicates the presence of metabolic activity, and can be used to measure the effect of the toxic substance.” This is an important factor because it enables scientists to gain a better understanding of the way specific categories of substances affect the human organism and understand why some of them are toxic while others have a therapeutic effect.