Sound waves are used in a lab-on-a-chip device to separate viruses from saliva

The development of antiviral therapeutics and vaccines requires a detailed study of the viruses that cause disease. But how can these small germs be isolated from complex biological samples such as saliva? Researchers in ACS Nano describe a platform that uses sound waves as acoustic tweezers to separate viruses from other compounds in a liquid. In demonstrations, the method quickly and accurately separates viruses from large and small particles in human saliva samples.

Isolating, identifying, and genetically sequencing a virus provides scientists with important information about how it causes disease and how to develop effective therapeutics. Current methods for separating viruses from other particles in biological samples involve time-consuming ultracentrifugation and cell culture procedures. To speed up and simplify the process, Luke Lee and Tony Jun Huang used acoustofluidics: a technology that uses sound waves to sort particles in a liquid by size. They chose a specific type of sound wave, called a Bessel beam, because it can be tuned to sort specific nanoparticles, and multiple waves stay tightly focused over long distances—like tweezers.

The Bessel Beam Excitation Separation Technology (BEST) platform developed by Lee, Huang and colleagues consists of a rectangular chip with a sample inlet at one end and separate virus and waste outlets at the other end. Two acoustic Bessel beams were passed across the chip perpendicular to the sample flow. By tuning the wavelengths of the beams, the system sorted particles of different sizes:

• Large particles with a diameter of over 150 nanometers (nm) were trapped on the chip.
• Small particles smaller than 50 nm are discharged through the waste outlet.
• Medium-sized viruses (50 to 150 nm) were collected via the virus outlet.

The team tested the BEST platform on human saliva samples loaded with SARS-CoV-2. The fluid collected from the chip's viral outlet contained 90% viral genetic material, while the fluid from the waste outlet contained no viral genetic material, demonstrating that the platform successfully isolated the virus. The researchers confirmed the results using electron microscopy and found viruses only in the fluid collected from the viral outlet. Although BEST cannot yet separate waste particles from viruses smaller than 50 nm, such as parvovirus, the researchers are working to expand the scope of the technology to enable its use in developing new therapeutic targets for numerous viral diseases.

Reference: Xia J, Wang Z, Becker R, et al. Acoustofluidic virus isolation using Bessel beam excitation separation technology. ACS Nano. 2024;18(33):22596-22607. doi: 10.1021/acsnano.4c09692

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