This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Being able to measure something plays a vital role in our ability to understand many phenomena. But measuring can often affect what we are trying to measure.
This is particularly the case when measuring substances that are very small, soft or fragile. In a recent study published in PRX Life, a research team led by the University of Osaka successfully used acoustic tweezers as a contactless method to investigate an important type of fragile material called biopolymer condensates. Biopolymer condensates are liquid-like droplets composed of proteins and/or nucleic acids and are involved in regulating a variety of physiological functions within cells to keep them healthy.
However, problems with these droplet systems can result in a variety of diseases, including neurodegenerative diseases. The mechanical properties of biopolymer droplets, such as fluidity and stiffness, are important for biological activity. Better knowledge of the mechanical properties of these droplets will help us understand their roles in healthy cells and disease states.
However, these droplets are very small and fragile and are difficult to investigate using conventional techniques. The multi-institutional team led by researchers from the University of Osaka developed an analytical tool called acoustic tweezers that uses ultrasound to investigate the mechanical properties of condensates without physically touching the material. "We fabricated a device that creates an acoustic force that can trap condensates at a specific point," explains lead author Kichitaro Nakajima.
As a proof of concept, the group investigated biopolymer condensates made of polyadenylic acid. These condensates are sensitive to salt concentration, so the research team expected that changing the salt concentration would cause changes in the mechanical properties of the droplets, which could then be measured using the acoustic trapping method. "We found that these condensates could be efficiently trapped and aligned based on the acoustic force in a contactless manner," says Nakajima.
"In addition, two condensates could be trapped to analyze what occurs when droplets merge." The team found that when acoustic trapping was applied, changes in the natural movement of a droplet in solution could provide information on the droplet's stiffness and the state of the molecules inside it. They then developed a framework to estimate a droplet's stiffness from its behavior in their sound-based trapping system. "This information is useful for understanding the mechanical properties of these droplets and hence their biological activity," explains Nakajima.
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