A microscopic carbon cloak made of graphene that could change the way bacteria and other cells are imaged because it protects the bacteria like a bed sheet. Pictured here is the difference in clarity of the cell walls.
Credit: Kansas State University
NEW YORK: A new microscopic 'cloak' could change the way that scientists capture images of bacteria and other cells, and the technology could help uncover new discoveries about life at the cellular level, recent research suggests.
By wrapping bacteria with graphene – a form of carbon that is only one atom thick - researchers in the U.S. are addressing current challenges with imaging bacteria under electron microscopes. The method creates a carbon cloak that protects the bacteria, allowing them to be imaged at their natural size and increasing the image's resolution.
"Graphene is the next-generation material," lead author and assistant professor of chemical engineering at Kansas State University, Vikas Berry, said. "Although only an atom thick, graphene does not allow even the smallest of molecules to pass through. Furthermore, it's strong and highly flexible so it can conform to any shape."
Microscope vacuum robs water
The team has been researching graphene for three years, and Berry recently saw a connection between graphene and cell imaging research. The material has several important properties: it's the strongest nanomaterial, is optically transparent and it has high thermal conductance.
Because it is also impermeable, Berry decided to use the material to preserve the size of bacterial cells imaged under high-vacuum electron microscopes.
The current challenge with cell imaging occurs when scientists use electron microscopes to image bacterial cells. Because these microscopes require a high vacuum, they remove water from the cells. Biological cells contain 70 to 80% water, and the result is a severely shrunk cell. As a result, it is challenging to obtain an accurate image of the cells and their components in their natural state.
Swaddling the bacteria in sheets
But Berry and his team created a solution to the imaging challenge by applying graphene. The graphene acts as an impermeable cloak around the bacteria so that the cells retain water and don't shrink under the high vacuum of electron microscopes. This provides a microscopic image of the cell at its natural size.
The carbon cloaks can be wrapped around the bacteria using two methods, outlined in the researchers paper that appears in the journal Nano Letters.
The first method involves putting a sheet of graphene on top of the bacteria, much like covering up with a bed sheet. The other method involves wrapping the bacteria with a graphene solution, where the graphene sheets swaddle the bacteria. In both cases the graphene sheets were functionalised with a protein to enhance binding with the bacterial cell wall.
