AsianScientist (Jul. 5, 2019) – Researchers at Osaka University have developed a method to help graphene reach its full potential as a bacterial biosensor by combining the specificity of antibodies with the sensitivity of microfluidics. Their results have been published in Nano Letters.
To get the bacteria to stick, the researchers covered the graphene with antibodies, a common way of anchoring bacteria to biosensor surfaces. However, although antibodies are very small, they are actually quite large and bulky compared to the atom-thin layer of graphene. The antibodies prevent the bacteria from being detected directly by the graphene through a signal blocking effect known as Debye screening.
To overcome the Debye screening limitation, the researchers decided to monitor chemical reactions being performed by the bacteria rather than the bacteria themselves. The chemicals produced in the reactions are far smaller than the antibodies and can slip between them easily and reach the graphene surface. By only analyzing the bacteria in tiny droplets generated through microfluidics, the bacteria and their reaction products can be kept close to the graphene surface and the concentration of the reaction products can even be monitored over time.
“Our biosensor enables highly sensitive and quantitative detection of bacteria that cause stomach ulcers and stomach cancer by limiting its reaction in a well-defined microvolume,” said study co-author Professor Kazuhiko Matsumoto.
The graphene sensing surface is able to generate electrical signals that vary depending on how much of the reaction product is present in the microdroplet and how quickly it is accumulating. These electrical signals can be used to calculate the number of bacteria in the droplet. The graphene biosensor is set-up in a field effect transistor (FET) structure to dramatically increase the electrical detection signals.
“Our biosensor is essentially a mini laboratory on a graphene FET. This sensor demonstrates how two-dimensional materials such as graphene are getting closer to being applied in practical medical and healthcare applications,” study first author Assistant Professor Takao Ono said.
As the device is able to detect even tiny amounts of bacteria in less than 30 minutes, it could speed up the diagnosis of potentially harmful bacteria, the researchers said. Furthermore, the system can also be modified to detect various different bacteria and create a whole host of similar “lab-on-a-graphene-FET” biosensors.
The article can be found at: Ono et al. (2019) Electrical Biosensing at Physiological Ionic Strength Using Graphene Field-Effect Transistor in Femtoliter Microdroplet.
Source: Osaka University; Photo: Shutterstock.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.