Apr 25 2019
Scientists at Tokyo Tech’s Laboratory for Chemistry and Life Science have produced a micelle-type nano-container that can be toggled between assembled and disassembled states through simple light illumination.
Chemical structures of the previous (left) and new amphiphile (right). Light irradiation induces a structural change from the open to the closed form of the amphiphile. (Image credit: Tokyo Tech)
The light stimulus causes a structural variation in the amphiphilic subunits, thereby closing their built-in binding pocket and at the same time leading to disassembly.
In the study published in the latest issue of Nature Communications, Lorenzo Catti (JSPS/Humboldt postdoctoral fellow), Natsuki Kishida, Michito Yoshizawa, and their collaborators successfully show how to integrate the use of light and water, both indispensable components for life, in an environmentally benign delivery system.
Water and light are abundant and clean resources on earth. Active use of both of them in synthetic and materials chemistry has seldom been accomplished so far but is an urgent necessity for the development of sustainable modern technologies.
Dr Michito Yoshizawa, Tokyo Tech
The success is based on a small design modification in the subunit of the nanosized container. The researchers moved the two polyaromatic panels on a previous amphiphilic compound one carbon atom closer together to facilitate a photochemical reaction between the panels that leads to quantitative closing of the binding pocket. Furthermore, the team could demonstrate that this reaction is partially and completely reversible by light illumination and heating, respectively.
The research is part of the team’s continuing effort toward environmentally benign nanoflask systems with controllable functionality. The new system can be regarded as an “aromatic micelle,” an idea that was presented by the group in 2013.
The absorption of water-insoluble guest molecules into the container was demonstrated to be easily achievable through a simple grinding protocol. By adding water to the resultant solids, characteristically colored solutions were produced, which exhibited UV-visible absorption bands assignable to the bound guest molecules. The adaptable nature of the nano-container enabled the absorption of a broad range of compounds, such as spherical fullerenes and planar, rod-shaped dyes in water.
It was possible to realize quantitative release of the guest compounds through the illumination of the aqueous solution for 10 minutes at room temperature. The released water-insoluble guests could additionally be recovered effectively through simple filtration, resulting in a clear colorless solution consisting of only the closed amphiphiles.
“In a biomedical context, the developed system holds great promise for future progress in non-invasive delivery of biomolecules and synthetic drugs,” concluded Dr Yoshizawa. Future enhancements of the system are aimed at enabling a weaker light source for irradiation, which will bring the system one step nearer to the envisaged in-vivo delivery application.