Designing Artificial Ion Channels

Researchers in South Korea have developed artificial ion channels that can transfer iodide ions 60 times more efficiently than chloride ions.

AsianScientist (Jun. 22, 2017) – Researchers at the Center for Self-Assembly and Complexity within the Institute for Basic Science (IBS) have created artificial ion channels for iodide. These findings, published in the Journal of the American Chemical Society, may lead to better diagnosis and treatment of iodide transport disorders.

The exchange of iodide (iodine ions) between cells and the bloodstream is crucial for the health of several organs and its malfunctioning is linked to goiter, hypo- and hyperthyroidism, breast cancer and gastric cancer. A protein known as the sodium/iodide symporter (NIS) controls the transport of iodide from the bloodstream into thyroid cells and other tissues, including mammary glands during lactation, cancerous breast tissues and lacrimal glands.

In the present study, scientists have developed synthetic ion channels that selectively allow the passage of negatively-charged ions, especially iodides. With a diameter of 3.64 nm and the right chemical characteristics, these channels called porphyrin boxes 1A (PB-1A), fit into the cellular membrane.

PB-1A has the shape of a 26-faced polyhedron made of triangles and squares, named rhombicuboctahedron by Archimedes. Two types of molecules make up 14 faces of the solid, while the other faces are left empty for the ions to pass through.

PB-1A has the advantage of being chemically stable in aqueous solution and in the cell membrane. The researchers found that PB-1A naturally inserts itself into the cell membrane, is functional as an ion channel and non-toxic to cells.

The team observed that different types of negatively-charged ions can go through PB-1A, but it has a strong preference for iodide. In fact, iodide transfer was about 60 times more efficient than for chloride, the most abundant negatively-charged ion in the body. This difference in efficiency is related to the water molecules surrounding the ions and the energy required to pull out them through.

“We are excited by these findings, because in comparison with studies on chloride channels and channels that transport positively-charged ions, iodide-selective artificial channels have been rarely reported in the last decade. Moreover, channels that mimic the functions of NIS are very interesting, as they have the potential to treat thyroid and non-thyroid malignancies,” said Dr. Roh Joon Ho, one of the corresponding authors of this study.

In the future, the researchers aim to develop smart synthetic ion channels gated by light.


The article can be found at: Benke et al. (2017) Iodide-Selective Synthetic Ion Channels Based on Shape-Persistent Organic Cages.

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Source: Institute for Basic Science.
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