Liquid 'Legos' Sense Light

A unique microscopic light sensor uses millimeter-sized water droplets and hair-thin electrodes to turn water droplets into protocells: empty, artificial cells that can be filled with different cellular components. In theory, networks of protocells could be used to simulate biological systems, such as heart muscle or brain tissue, or even artificial eyes.

“Each millimeter-sized water droplet in our network acts as a protocell," said Matthew Holden, a chemistry professor at Oxford who conducted the research with Oxford’s Professor Hagan Bayley and David Needham at Duke University. "Chains of droplets are put together like liquid Legos, and are just as easily taken apart or reorganized.”

Microscopic light sensors created using millimetre-sized water droplets and hair-thin electrodes. (Photo: University of Oxford) Diagrams and a video of the process can be viewed at: www.chem.ox.ac.uk

The scientists took a protein (bacteriorhodopsin) normally used by bacteria to produce energy and incorporated it into a network of droplets. This protein reacts to green light by pumping protons across a cell membrane, which creates a positive electrical charge. By piercing the droplets with hair-thin electrodes, they can measure the current with a sensitive amplifier. In the future, such droplets could be arranged to form ‘pixels’ in an imaging array -- acting as an artificial eye.

"Using protocells to simulate biological systems offers significant advantages to working with live cells, where there is far less control over their contents, size and function," said Holden. "Many living cells do not survive outside a narrow temperature range and are extremely sensitive to environmental conditions, such as pH. In the long run, protocell-based systems could reduce the cost and complexity of biological experiments and, in some cases, might be used in place of animal testing."

Although protocells have provided biological and evolutionary insights before, this is the first time they have been shown working together to perform a function. The researchers hope to create increasingly complex systems as a stepping-stone toward understanding a variety of biological function, from nerve impulses to heartbeats.

Their research was recently published in the Journal of the American Chemical Society.

For more information, visit: www.chem.ox.ac.uk/bayleygroup/bionetworks/index.html