As well as boasting a number of unique electronic and mechanical properties, graphene, which is a sheet of carbon just one atom thick, also encourages the growth and adhesion of mesenchymal stem cells on its surface, explains co-team leader Massimiliano Papi of the Catholic University of the Sacred Heart in Rome. This is because it can act as a pre-concentration platform for osteogenic inducers.

Graphene and its oxidized form, graphene oxide (GO), can in fact help stem cells differentiate into bone tissue with varying efficacy depending on the reductive state of the material, he adds. It is thus possible to control osteogenic processes and bone mineral density on its surface by controlling the oxidative state of GO.

Nanowrinkles define how stem cells orientate on the GO

In their work, Papi and colleagues completely covered the surface of a scaffold with GO nanoflakes. The scaffold can be made from any material they choose. They then used a laser beam to “write” on the GO flake surface, which is essentially flat. This beam locally removes oxygen groups from the GO and generates nanowrinkles in the material.

“It is these nanowrinkles that are able to define how stem cells orientate on the GO,” Papi tells nanotechweb.org. “This is because the cells prefer to attach themselves onto the hydrophobic and rough reduced-GO structure rather than the hydrophilic flat GO surface.”

GO nanowrinkles are also antibacterial

And that is not all: the researchers say that the reduced nanowrinkles are also antibacterial and help reduce the activity of bacteria like methicillin-resistant Staphylococcus aureus (MRSA), which is a common cause of prosthetic joint infections. “The nanowrinkles in fact have sharp edges and damage bacterial membranes by penetrating them like a knife,” explains Papi.

“In our work, we have shown that it is possible to control how stem cells migrate, orientate and accumulate on a surface specially designed with a specific laser pattern,” he says. “Our strategy might revolutionize regenerative medicine and surgery because it allows us to design scaffolds able to produce a ‘personalized’ bone structure on an antibacterial surface.”

The team, reporting its work in 2D Mater. 5 015027, says that it will now be testing its laser-printed GO surfaces on organ-on-chip devices. “These are multi-channel microfluidic cell cultures that simulate the activity, mechanics and physiological response of entire organs and organ systems,” says Papi.