Cell Membranes Can Be 'Written' Directly on to Graphene Surface

Cell membranes can be directly "written" on to a graphene surface using a technique called Lipid Dip-Pen Nanolithography (L-DPN), researchers from the University of Manchester write in the journal Nature Communications.

A single layer of carbon atoms bonded together in a repeating pattern of hexagons, graphene is so thin it's considered two dimensional and holds the prestigious title of world's strongest material.

Now researchers have shown that graphene can be used as a surface on which to assemble model cell membranes. Doing so, the study's authors explain, represents an important step in allowing scientists to more closely examine the systems and processes that occur in cell membranes -- a task difficult to carry out when studying live cells inside the human body.

Graphene contains several advantages over existing surfaces due to its unique properties, the study's authors found.

"Firstly, the lipids spread uniformly on graphene to form high-quality membranes," co-author Aravind Vijayaraghavan said in a statement, adding that the material boasts "unique electronic properties; it is a semi-metal with tuneable conductivity."

"When the lipids contain binding sites such as the enzyme called biotin, we show that it actively binds with a protein called streptavidin," Vijayaraghavan explained. "Also, when we use charged lipids, there is charge transfer from the lipids into graphene which changes the doping level in graphene. All of these together can be exploited to produce new types of graphene/lipids based bio-sensors."

The way L-DPN works is by using an extremely sharp tip to write lipid membranes onto surfaces much like a quill pen with ink on paper.

"The small size of the tip and the precision machine controlling it allows of course for much smaller patterns, smaller than cells, and even right down to the nanoscale," co-author Michael Hirtz said.

Furthermore, by using a number of these tips, Hirt explained, "different mixtures of lipids can be written in parallel, allowing for sub-cellular sized patterns with diverse chemical composition."

Besides bio-sensors, the study's findings could have implications for areas such as bio-catalysis and drug delivery, the researchers said.