There has been a deluge of scientific investigation into the application of graphene and other two dimensional (2D) materials in biomedicine in the recent past. Claims range from proof of concept detection of glucose, Hemoglobin, Dopamine, DNA etc all the way to products that aid in analysis of proteins, peptides and aptamers.
So how can such atomically thin sheets help in diagnosing or studying certain diseases?
Every material has a surface where its atoms interact with the external world and a bulk which are the atoms that sit below the surface. By its very nature 2D materials have no bulk as all its atoms are the surface itself. This means sensors fabricated from these materials exhibit unprecedented levels of sensitivity as any change in its properties due to the presence of chemical or biological species is not lost in the bulk response.
San Diego based firm Nanomedical Diagnostics Inc. have recently started shipping field effect biosensing chips made from CVD graphene. These devices are used to study activity assays in drug discovery and life science research. Researchers from University of California San Diego (UCSD) have achieved comparable or better data with these sensors than conventional tools while working with 1/1,000,000th the sample size. The firm also reports successful scale up of their fabrication technology up to 150 mm wafer scales and envision taking it to 200 mm scales in the future. The beauty in this achievement is that they are one of the first companies to scale a field effect sensing technology while achieving 90% yield over 7000 transistors!
Another great example of this property of 2D materials is the work done by researchers at Uni. Illinois at Chicago. Dr Berry and colleagues have used CVD graphene to detect cancerous cells using Raman spectroscopy. They lay brain cells onto graphene and show that they can differentiate a single hyperactive cancerous cell from a healthy cell. There is a change in the atomic vibrations in graphene due to the change in its charge distribution, depending on the nature of the cell which can be probed by Raman spectroscopy.
Turning the sensing principle on its head, several researchers across the world have used pores Instead of the surface in Graphene and MoS2. Translocating DNA strands across these pores, shows identification of single nucleotides. 2D MoS2 seems especially promising due to its longer stability of detection before additional functionalisation to reactivate the sensor. This technique holds great promise as it builds and improves on SiNX and HfO2 based BioMEMS by using 2D material membranes.
There are several promising examples of the application of 2D materials for biomedicine. However there are also many challenges to overcome before you can walk into a doctor’s surgery and ask for a blood or tissue sample to be placed on a graphene based Raman sensor to instantly quantify the presence or extent of a disease.
This would require years of research and study of regulatory issues. This is because there are many challenges which need to be addressed. A simple example is the detection of the required target species in a mixed heterogeneous analyte or in simpler terms the issue of specificity. For example, can the device differentiate between dopamine and hemoglobin by dropping a sample of blood on the detector? We are not yet there when it comes to point-of-care devices but there is definitely great promise in laboratory applications such as the one commercialized by Nanomedical Diagnostics Inc.
At Plasma Technology we specialise in depositing and etching 2D materials via several techniques as well as fabricating materials for device structures – read more at www.oxinst.com/ASP. Are you using 2D materials for biomedical research or are interested in such applications? If so please write in, comment, tweet or message us on LinkedIn. We would love to hear more and learn from you!