Scientists put nanomotors in motion in artificial cells

The bacterium Listeria monocytogenes is the last thing you want inside your cells — it can make you seriously ill. But now, a research team at Aarhus University has used its unique mode of movement as inspiration to build nanomotors that they place inside artificial cells. This gives the artificial cells a function otherwise only seen in living cells.

No one has yet created a fully functioning artificial cell. But a research team at Aarhus University has taken a step in that direction:

They have equipped artificial cells with tiny motors inspired by an unusual movement mechanism found in nature – specifically from the bacterium Listeria monocytogenes. The result: artificial cells that can form internal networks of protein filaments – a function otherwise unique to living cells. The study is published in ACS Nano.

Inside living cells, Listeria monocytogenes propels itself forward by forming long filaments of the protein actin (a structural protein found throughout the cell), which push it ahead like a microscopic rocket engine. The researchers mimicked this principle at the nanoscale.

“We wanted to find out whether nanomotors – nanoparticles capable of moving via actin polymerization – could help us build a kind of internal skeleton inside artificial cells,” explains Miguel A. Ramos-Docampo, Assistant Professor at the Interdisciplinary Nanoscience Center (iNANO) at Aarhus University. “The nanomotor uses a movement mechanism invented by nature – but we use it for a very different purpose.”

Motors trigger internal network formation

The artificial cells consist of vesicles – membrane-bound spheres with a liquid lumen – into which the researchers embedded the nanomotors. On the surface of these motors, actin polymerization was activated, causing long protein filaments to grow in all directions. At the same time, the nanomotors started moving faster as the actin filaments pushed them forward – just like Listeria. The resulting network resembles the cytoskeleton (the cell’s internal scaffold and transport network) found in living cells.

However, unlike natural cells, where movement and organization are controlled by complex biological signalling, the artificial cells and nanomotors rely on a simpler mechanism.

“Our artificial cells don’t move or organize like real cells. But by repurposing Listeria’s propulsion strategy, we can make synthetic systems that self-organize,” says Brigitte Städler, Professor at iNANO.

Collaboration across disciplines

The research team combines expertise in chemistry, biophysics, nanotechnology, and mathematics. This interdisciplinary collaboration was essential for understanding and modelling how the tiny motors move and organize inside the artificial cells.

Specifically, the researchers have broken new ground by integrating two different and distinct research areas, that are usually not investigated together:

• artificial cells, which are at the core of bottom-up synthetic biology,
• and nanomotors, which is an area of research that typically would be associated with active matter (systems capable of self-propulsion)

“Living systems are extremely complex,” says Brigitte Städler. “Mimicking even a small part of their behaviour requires combining experiments, theoretical modelling, and nanotechnological design. This work demonstrates how motion and structural organization can be linked within one coherent system.”

A first step toward self-organizing man-made cells

In living cells, the cytoskeleton is a dynamic structure that constantly assembles and disassembles. The artificial version is still far from that level of complexity, but the study shows how motion and internal organization can emerge in synthetic systems.

“This is an early step, but it helps us understand what it takes to mimic even a small part of a cell’s function,” says Miguel Ramos-Docampo. “It shows that we can build functionality from the bottom up – without copying all of biology’s complexity.”

They are now exploring how to design artificial cells that can not only form internal structures but also respond to their environment or interact with living cells.

“We’re not trying to recreate life,” says Brigitte Städler. “We’re trying to understand and replicate selected life-like functions. Our artificial cells are simple and stable, and we can program their behaviour. That opens new doors for both fundamental science and future technologies”

Fact box: How Listeria monocytogenes moves

The bacterium Listeria monocytogenes moves inside living cells by hijacking the cell’s own machinery. It builds filaments of actin, which grow behind the bacterium and push it forward – like a tiny biological rocket. This so-called “actin comet tail” mechanism inspires researchers to create nanomotors that can move and self-organize in similar ways, but without being alive or infectious.