"Concentriosome": A Compartment Without Permanent Boundaries

We have unearthed a new artificial organelle known as “Concentriosome” to carry out spatiotemporal enzymatic cascade reactions in solution and regiospecific chemical events using the standing waves that in turn are generated by the Faraday Instability setup.
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Compartmentalization or spatial organization of biological molecules in a complex system is foundational to life. It helps in increasing the efficiency of many subcellular processes by concentrating the required components to a confined space within the cell, maintaining out-of-equilibrium situation, isolation of incompatible components, etc. Biological systems perform many catalytic events or cascade reactions using compartmentalization, for e.g. protein synthesis. To ape, scientists have discovered several artificial counterparts including vesosomes, polymersomes, proteinosome, coacervates, etc. in the last decades and carried out cascade reactions.[1,2] However, they are made by taking advantage of electrostatic interactions or structure aiding molecules.

In contrast to this, Dhasaiyan and co-workers from IBS lead by Prof. Kim has developed a strategy to make a new membraneless concentric compartment, so-called “Concentriosome”. The team has recently reported a new way to control the  patterns in out-of-equilibrium systems in 2020.[3] We now found that the solution was transiently separated and not mixed together for a certain period of time due to the node region of the wave and an invisible wall blocked different layers and hence the solution becomes naturally compartmentalized (Scheme 1).

Scheme 1. Schematic representation of the surface standing wave generation and regiospecific distribution of reactive species used for the enzymatic cascade reaction network.

The “Concentriosome” has several distinct features compared to the existing systems (Figure 1). To mention a few, they are transient,  rate of reaction is different at different compartments and can be modulated spatiotemporally using an inhibitor (shown in paper). Additionally, the number of compartments in the “Concentriosome” can be varied by using frequency and dish sizes that is quite strenuous or not feasible to have such behaviour with the well-studied systems.[4]

Figure 1. A. The traditional compartmentalized model (vesosomes or polymersomes) studied in the literature and B. photograph of Concentriosome developed and used for the enzymatic cascade in the present study.

The team demonstrated the enzymatic cascade reaction using Glucose/GOx/HRP/ABTS system. The formation of the compartments was visualized as bluish cyan color (resulting from the oxidation of ABTS to ABTS+.) upon exposure to liquid vibration. The team further expands their approach beyond the molecular level also. We attained predetermined growth and alignment of Au nanoparticles as well as different extent of self-assembly of Au nanoparticles in solution; a deadlock among chemists and materials scientists for several decades (Figure 2A and B). We are also successful in obtaining the preparation of nanoparticle-patterned hydrogels, which contained self-assembled nanoparticles only in selected regions and used them in regiospecific cell growth (Figure 2C).

Figure 2. A. Spatiotemporal self-assembly of gold (Au) nanoparticles, B . insitu growth and predictable alignment of Au nanoparticles in solution, and C. fluorescent images of HeLa cells from nanoparticle patterned hydrogel revealing the selective cell growth on the patterned hydrogel matrix. The TEM images from figure A correspond to the extent of different self-assembly at the nodal and antinodal zone at a particular time. Likewise, TEM images in figure B show the different sized nanoparticles present in the solution. 

In principle, the “Concentriosome” developed by us is similar to polymersomes or vesosomes, a sphere-shaped artificial vesicles consisting of concentric series of multiple bilayers that are popular since mid-60s.[5] Although currently there is no loading and delivery of guests is not shown with “Concentriosome”, at this time the team believes, this is entirely a brand new method in the areas of compartmentalization strategies over the last 60 years of development (Figure 3). Moreover, this may provide a reliable strategy for regiospecefic control over chemical processes within a predictable position in a solution. This will have considerable implications in several interdisciplinary areas including tissue engineering.

Figure 3. The artificial systems used for mimicking compartmentalization and the corresponding years of development.

References:

1. Buddingh, B. C. & van Hest, J. C. M. Artificial cells: synthetic compartments with life-like functionality and adaptivity. Acc. Chem. Res. 50, 769–777 (2017).

2. Schoonen, L. & van Hest, J. C. M. Compartmentalization Approaches in Soft Matter Science: From Nanoreactor Development to Organelle Mimics, Adv . Mater., 28, 1109-1128 (2015).

3. Hwang, I. et al. Audible sound-controlled spatiotemporal patterns in out-of-equilibrium systems. Nat. Chem., 12, 808–813 (2020).

4. Dhasaiyan, P. et al. Cascade reaction networks within audible sound induced transient domains in a solution, Nat. Commun, 13, Article number: 2372 (2022).

5. Bangham, A. D., & Horne, R.W. Negative staining of phospholipids and their structural modification by surface-active agents as observed in the electron microscope. J. Mol. Biol., 8, 660–668 (1964).