Graphene in biomedicine
The May editorial of Nature Materials discusses the recent launch of a Work Package on Biomedical Technologies by the Graphene Flagship, and highlighted the questions that researchers in the field will try to answer in the next few years.
Among the different applications being currently explored for graphene and other 2D materials, diagnostic and therapeutic medical tools certainly have huge commercial potential. However, will the performance and fabrication costs of graphene-based devices ever be able to compete with those of Silicon lab-on-chips, metallic electrodes for brain stimulation and flexible neural recording sensors based on organic semiconductors or other materials?
A sensible approach to answer this riddle is trying to understand which physical and chemical properties of graphene can make the difference in such applications. For instance, membranes of monolayer graphene are ion-impermeable, yet they can be patterned to create nanopores that allow the controlled transport of ionic currents, polymer chains and DNA molecules. These architectures have been studied for DNA sequencing applications, although several practical challenges remain to be solved. Graphene can also be easily functionalized , which may prove advantageous for the fabrication of efficient drug delivery systems. Single or few layers of graphene or graphene oxide could be used as carriers that immobilize drugs on their surface and release them only in proximity to a specific target in the body. First, however, it’s essential to understand how cells and organs react to graphene, and it seems now clear that systematic studies on how the biocompatibility of 2D materials is affected by their size, structural integrity and chemical functionalization will be required to address this point.
As a final example, it is worth mentioning that also the electronic properties of graphene may be leveraged to realize advanced biomedical devices. A high charge mobility improves the sensing performance of transistors used to record the electrical activity of neurons, and indeed flexible graphene transistors that detect the action potential generated by cell cultures with sensitivity comparable with Silicon transistors have been recently reported. Scaling up this technology and translating it into in vivo applications — for example to realize devices able to record the brain activity from more than 1,000,000 neurons simultaneously, as required by a recent call for proposals from DARPA — is a massive engineering challenge that will certainly need much more work, and it is not clear at this stage if graphene will be the winning solution in bioelectronics on the long term.
For those interested in learning more about the potential of graphene in biomedicine, Nature Materials, Nature Physics and the Graphene Flagship are organising a Nature Symposium on Biomedical Applications during the Graphene Week conference coming next June. Stay tuned.
Luigi Martiradonna (Nature Materials)