Can you tell by looking at it whether an avocado is hard or soft? This would require recognizing how the plant cells behave behind the skin. The same applies to all other cells on our planet: despite more than 100 years of intensive research, many of their properties remain hidden within the cell. In their recent publication in Nature Materials, researchers from the University of Göttingen describe a new approach that can determine the particularly difficult-to-detect mechanical properties of the cell interior by taking a closer look.
Cells are the basic units of all life and their precise understanding is a key factor in the progress made in medicine and biology. Nevertheless, research into it is still a challenge because many methods destroy the cell during analysis. Researchers from the University of Göttingen now pursued a new idea: they used the random fluctuating motion that all microscopic particles perform. To do this, they first simulated the expected fluctuations and then checked the predictions using optical laser traps that can precisely monitor microparticles. Using this approach, the research team was able to analyze the movement of microscopic particles – with precision in the nanometer range and a time resolution of about 50 microseconds. In addition, the analysis also takes into account history, that is, past movements. It turned out that many objects, after being moved randomly, always want to return to a certain place. The researchers used this tendency to return to a previous position to define a new quantification called mean back relaxation (MBR).
This new variable now serves as a kind of fingerprint: it contains information about the causes of the observed movements. This makes it possible for the first time to distinguish active processes from purely temperature-dependent processes (Brownian motion). “With MBR we can obtain more information about the object motions than is possible with conventional approaches,” explains Professor Matthias Krüger from the Institute for Theoretical Physics of the University of Göttingen.
To make statements about living cells, the researchers applied the method to the inside of living cells. “Because our knowledge of the inside of cells is still limited, it was initially unclear whether the MBR could also be applied here. When I saw the resulting curves, I could hardly believe my eyes, because the inside of cells could be described very precisely. using the approaches we had originally developed for much simpler situations,” marvels Professor Timo Betz from the Third Institute of Physics, head of the experiments.
“The results show that the combination of close observation and new, intelligent analysis methods can provide insight into whether the inside of cells is soft, hard or liquid,” says first author of the study, Till Münker from the Third Institute of Physics . The work was co-financed by the European Union as part of an ERC Consolidator Grant.
