Press release: Shape-shifting cells at the flick of a switch

No. 104 - 27.06.2023

Research team with Göttingen University uses light to reversibly change the shape of red blood cells

Membranes are crucial to the functioning of living cells: they separate the cells from the environment and protect them; they transport nutrients into the middle of the cell; and they are vital when cells grow together to form tissues, reproduce by division or move around. Researchers from the Universities of Göttingen and Münster have now described for the first time how living cells can be changed reversibly by targeting the cell membrane with light. In their laboratory experiment, red blood cells took on a spiked shape thanks to a built-in "molecular light switch" when illuminated with visible light. When exposed to UV light, they flattened out into their natural disc shape. The process could be repeated several times. The study was published in Nature Communications.

Normally, red blood cells have a flat disc shape and are called “discocytes”. However, they can also be a spiked shape – known as an “echinocyte” from the Greek word for hedgehog or sea urchin – with small, evenly spaced thorny projections on the surface. The researchers have now succeeded to control the switch between the two forms in red blood cells. They built a "molecular light switch" into the cell membrane: a molecule that has a similar structure to the molecules of the cell membrane itself, but also has a function that changes its shape when illuminated. The chemical involved is an “azobenzene”.

"Since the azobenzene has hydrophobic properties, meaning that it repels water, we have also added a hydrophilic part in the form of a side-chain of water soluble molecules. This is a design that is very close to the lipid molecules of cell membranes that occur in nature," explains first author Dr Fabian Höglsperger from the University of Münster. "The differences between the molecule azobenzene-TEG-SO3H, which we designed and produced, and the naturally occurring lipid molecules are small. But these small differences are just enough to mean that the properties of the artificial molecule can be changed by light."

The incorporation of the azobenzene caused the cells to suddenly switch to their spiked shape. When irradiated with UV light, the cells changed back to the disc-shaped discozytes. The researchers explain this with a structural change of the azobenzene molecule. It causes the thorny projections of the cell membrane to flatten. Under visible light, the cells went back to their flat shape, because the light triggered the reverse reaction of the "molecular light switch".

Professor Timo Betz from the Faculty of Physics at Göttingen University sees many potential uses for this. “Using this approach, we can change the membrane area and thus the membrane tension of cells in a simple and targeted way, exactly when and where we want. In recent years, it has been shown that membrane tension is an important variable that influences cellular processes."

At the moment, this is at the basic research stage. However, those involved emphasise: "In the future, this simple and efficient method could help to study the reactions of cells to their environment depending on their shape or to control processes such as cell division and cell migration simply by using light."

Original publication: Fabian Höglsperger et al. “Rapid and reversible optical switching of cell membrane area by an amphiphilic azobenzene”, Nature Communications (2023). DOI: 10.1038/s41467-023-39032-0

Contact:

Professor Timo Betz

University of Göttingen

Faculty of Physics – Biophysics Institute

Friedrich-Hund-Platz 1, 37077 Göttingen, Germany

Tel: +49 (0) 551 39 26921

Email: timo.betz@phys.uni-goettingen.de