The researchers could monitor how hundreds of cells move in the presence of acoustic waves. From these motions, they inferred the sizes, mechanics, and internal structures of individual cells. This research was published recently in ACS Nanoscience Au – the open-access version of high-profile journal ACS Nano – and is also on the cover of the journal. This novel technique opens many new possibilities for cell and synthetic biologists. As microparticles make an excellent sample to study with Quantitative Acoustophoresis (Greek: sound + motion), the material scientists should also take a closer look at the method.
“Our cells are much more complex than one can assume. They can move around, change shape and interact with the surroundings”, says VU PhD student Vadim Bogatyr, the paper's first author. “None of these behaviours would be possible without the constantly growing and changing scaffolding inside the cells called cytoskeleton (Greek: cell + skeleton). Its properties and composition vary for healthy and sick cells, blood and connective tissue cells, and cells in normal conditions and under the effects of chemicals. Our method lets us quickly measure these mechanical differences.”
Method without probes or labels
“If you want to find out how soft and ripe the mango is, you touch it. That’s the underlying idea of many techniques used to measure cell mechanics”, explains Bogatyr. “Scientists employ various microscopic objects to poke, squeeze and stretch the cells. But cells are not mangoes: they are alive systems that can actively respond to these local deformations. That is why we aimed to develop a method without probes or labels. The cells are floating in a liquid and are pushed by the sound vibrations. This push arises from the differences in the properties of the cells and the solution. The larger, denser, and cytoskeleton-rich cells move the fastest.”
In addition, this approach is not damaging to the cells, while some other methods only work with dead and fixated cells. Plus, most methods can only measure a single cell at a time, requiring weeks of measurements instead of hours for Quantitative Acoustophoresis to obtain the same data. “With Quantitative Acoustophoresis, one can potentially measure the same cells for long periods and track all the mechanical changes that happen to them as they develop, grow and divide during their life span. Plus the setup is relatively easy to construct, making sure other labs can also make use of our method”, adds VU Professor Gijs Wuite.
The research is part of the Building a Synthetic Cell (BaSyC) project and was financed by a "Gravitation" grant from the Dutch Ministry of Education, Culture, and Science, in cooperation with the Netherlands Organization for Scientific Research (NWO), and by the participating research institutions: TU Delft, Radboud University, Wageningen University, University of Groningen, AMOLF and VU Amsterdam.