A team led by the University of Osaka has developed acoustic tweezers that use ultrasound to trap and manipulate biopolymer condensates without physical contact. These condensates are liquid-like droplets composed of proteins and nucleic acids that regulate cellular functions, and their dysfunction is linked to neurodegenerative diseases.
Conventional techniques struggle to measure the mechanical properties of such small, fragile droplets because touching them alters their behavior. The new device creates an acoustic force field that holds a droplet at a fixed point in solution, allowing researchers to observe its natural movement and response to merging with another droplet.
As a proof of concept, the team studied condensates made of polyadenylic acid, which are sensitive to salt concentration. By varying the salt level and tracking how the trapped droplets moved and fused, the researchers built a framework to estimate droplet stiffness from their dynamics in the acoustic trap.
Lead author Kichitaro Nakajima said the method efficiently trapped and aligned the condensates and enabled analysis of what happens when two droplets merge. Changes in a droplet's motion under acoustic trapping provided information on its internal molecular state and mechanical stiffness.
The researchers reported their findings in the journal PRX Life. The acoustic tweezers offer a way to profile the mechanical properties of soft biomolecular materials that are otherwise difficult to study, potentially aiding the understanding of their roles in healthy cells and disease.
The work was conducted by a multi-institutional collaboration and published under DOI 10.1103/kl9v-5ywv. The team suggests the tool could help uncover new treatment strategies for diseases associated with biomolecular droplet dysfunction.
Sound-based traps reveal how fragile biomolecular droplets move, merge and change stiffness
This is an independent summary. The complete reporting, supporting context and any primary documents remain with Phys.org.