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bmp Graphene is only recently finding its way into biomedical applications. Most of the recent work in this area focuses on using graphene as a biosensor, i.e. as a passive medium, which monitors some external stimulus, usually by taking advantage of the fact that graphene's resistance depends strongly on nearby electric fields and signals (see for instance: "Graphene-DNA biosensor selective, simple to create"). But this is from a fundamental point of view nothing new; silicon wires, diamond films and carbon nanotubes all have been already used for this type of application.


In our work, we show that graphene can be used in a more active way in biomedical applications, i.e. it can control the fate of a stem cell," Barbaros Özyilmaz, an assistant professor in the Department of Physics at National University of Singapore (NUS), explains to Nanowerk. "The reason why this actually happens is not clear, but it is almost certainly due to a mix of the many outstanding and unique properties of the graphene sheet, i.e. its 2D nature, its mechanical, chemical and electrical properties." Özyilmaz points out that the downside of this lack of understanding is that it is hard to pinpoint why exactly the use of graphene leads to stem cell differentiation. "But we are working on understanding this now in more detail. My group recently got a US$500k grant to study the graphene cell interface – this is not directly related to the stem cell work, but is meant to create a combined AFM-optical-electrical characterization set-up uniquely for understanding how the cell exerts a force on graphene and vice versa." Reporting their findings in a recent issue of ACS Nano ("Graphene for Controlled and Accelerated Osteogenic Differentiation of Human Mesenchymal Stem Cells"), a NUS team working with collaborators from Sungkyunkwan University in South Korea, show that graphene provides a new type of biocompatible scaffold for stem cells. In their experiments, the researchers studied the influence of graphene on stem cell growth by investigating four substrates with widely varying stiffness and surface roughness.

polydimethylsiloxane (PDMS); polyethylene terephthalate (PET); glass slide; and silicon wafer with 300 nm silicon dioxide. They performed two distinct sets of experiments: First, cell viability was studied with cells cultured in normal stem cell medium. Next, stem cell differentiation was examined in cells cultured on conventional osteogenic media. The team's motivation was to go beyond related experiments that were performed with carbon nanotubes. However, carbon nanotubes need to be functionalized, they come in a number of different forms and chirality, and from a practical point of view it is not clear how safe such they are. Maybe most importantly, it would be difficult to fully cover a surface with carbon nanotubes and use them as coating material which can simultaneously act as a barrier.

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