Using sound to control enzymatic reactions
- Unhackneyed compartmentalization generated by audible sound allows the enzyme reactions to be
controlled spatiotemporally -
Spatiotemporal regulation of multistep enzyme reactions through compartmentalization is essential in studies that
mimic natural systems such as cells and organelles. Until now, scientists have used liposomes, vesicles, or
polymersomes to physically separate the different enzymes in compartments, which function as ‘artificial
organelles’. But now, a team led by Director KIM Kimoon at the Center for Self-assembly and Complexity within
the Institute for Basic Science in Pohang, South Korea successfully demonstrated the same spatiotemporal
regulation of chemical reactions by only using audible sound, which is completely different from the previous
methods mentioned above.
Sound has been widely used in physics, materials science, and other fields, but has been rarely used in
chemistry. In particular, audible sound (in the range of 20-20,000 Hz) has not been used in chemical reactions
so far because of its low energy. However, for the first time, the same group from the IBS had previously
successfully demonstrated the spatiotemporal regulation of chemical reactions through a selective dissolution of
atmospheric gases via standing waves generated by audible sound back in 2020.
Later, they closely observed the movement of the solution induced by the audible sound and found that the
solution was separated and not mixed together due to the node region of the wave as if the different layers were
blocked by an invisible wall. They called this transient domain of the solution created by audible sound
“pseudo-compartmentalization”, and used it to control enzyme-based cascade reaction networks in a solution. In
this phenomenon, the flow of fluid that is induced in a container vibrating up and down by audible sound does
not mix with each other around the node of the wave, and as such, the solution becomes naturally
compartmentalized.
This new finding inspired the group to use this phenomenon to attempt spatiotemporal regulation of multistep
enzyme reactions. Normally, doing this requires artificial compartments to be created using lipids or polymers
are generally used, but Kim’s group showed that such can be possible using only audible sound. To achieve this,
they designed a clever system by taking advantage of the fact that oxygen in the air is dissolved only in the
antinode region of the vibrating solution (Figure 1).
To test this system, Kim’s Group performed a multistep enzyme reaction composed of glucose oxidase (GOx) and
horseradish peroxidase (HRP). In the first step, the enzyme GOx catalyzes the oxidation of glucose and produces
hydrogen peroxide. This peroxide is then used by the enzyme HRP to fuel the second step, which involves the
oxidation of colorless ABTS dye into cyan-colored ABTS radical. The researchers would know that their system
worked as intended if the cyan color appeared at specific regions in the solution.
As expected, the authors were able to visually observe cyan-colored concentric ring patterns, which confirmed
that they succeeded in spatiotemporal control of the GOx-HRP cascade reaction using only audible sound (Figure
2). The authors further showed that this method can be extended to control the redox-driven in situ growth or
pH-responsive self-assembly of nanoparticles within spatiotemporal domains present in the solution. (Figure 3A).
In addition, the authors also presented the preparation of nanoparticle patterned hydrogels, which contained
self-assembled particles only in selected regions. These gels can be used in region-specific cell growth
platforms (Figure 3B).
“This new approach using audible sound will provide a totally new and reliable strategy to control chemical
processes within predictable yet transiently generated pseudo-compartments within a solution”, explains Director
Kim.
Figure 1. Audible sound-induced generation of transient domains and spatiotemporally controlled cascade
reaction networks.
Figure 2. Audible sound-mediated spatiotemporal control over glucose/GOx/HRP/ABTS cascade reaction. (A)
Schematic representation of glucose/GOx/HRP/ABTS cascade reaction. (B) The random shaped pattern generated
without applying audible sound (C) Time-dependent changes of a concentric ring pattern obtained by applying
an audible sound input (40 Hz).
Figure 3. (A) Audible sound and enzyme-mediated spatiotemporal control of gold nanoparticle assembly.
Colored concentric patterns and TEM images were taken from each region of the pattern. (B) Nanoparticle
patterned hydrogel (left) and its utilization for selective cell growth (right). In the fluorescent microscope
image, red spots represent HeLa cells on the patterned hydrogel surface.
Notes for editors
- References
Prabhu Dhasaiyan, Tanwistha Ghosh, Hong-Guen Lee, Yeonsang Lee, Ilha Hwang, Rahul Dev Mukhopadhyay,
Kyeng Min Park, Seungwon Shin, In Seok Kang, and Kimoon Kim, Nature Communications, 2022, DOI:
10.1038/s41467-022-30124-x
- Media Contact
For further information or to request media assistance, please contact Director Kimoon Kim
(kkim@postech.ac.kr), Ilha Hwang (ihwang1@ibs.ac.kr), Rahul Dev Mukhopadhyay (rdevmukherjee@gmail.com), or
William I. Suh at the IBS Communications Team (willisuh@ibs.re.kr).
- About the Institute for Basic Science (IBS)
IBS was founded in 2011 by the government of the Republic of Korea with the sole purpose of driving
forward the development of basic science in South Korea. IBS has 1 research institute and 34 research
centers as of May 2022. There are eleven physics, three mathematics, seven chemistry, seven life science,
one earth science, and five interdisciplinary research centers.