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Graphene sensors are at the forefront of graphene electronics commercialization efforts, and more graphene sensors have come to market than any other graphene-enhanced electronic device. Among graphene sensors, biosensors have the largest market share. Cardea is one company that has in the past released graphene-enhanced biosensors using its biosignal processing unit (BPU) for cancer detection.
Cardea is now expanding its graphene biosensor offerings and recently received a $1.1 million grant from the Bill & Melinda Gates Foundation to develop an “electronic nose” using the graphene BPU module to diagnose infectious diseases in human breathing.
It started with the discovery of cancer
Cardea’s entry into the graphene biosensor space began with offering an alternative route to biopsy for cancer detection. Traditional biopsies are tissue biopsies, but they are very invasive and often do not offer any form of early warning detection. Over the years, liquid biopsies have become more common because they are less invasive and can detect cancer from body fluids. Cardea builds on this trend and uses a graphene transistor platform within the BPU to improve the biopsy detection process.
These graphene-enhanced cancer sensors use next-generation sequencing to offer a way to detect different types of cancer. Most cancers can be detected using various biopsy methods, but Cardea uses the graphene platform to detect multiple cancers in a single liquid sample – offering a way to detect cancer early if the source of the cancer is unknown.
The BPU platform can analyze different biosignals from multiple communication channels in the body, in an approach known as multiomics (the study of the different ‘omics’). Thus, the platform can analyze nucleic acid biosignals (genomics) and amino acid biosignals (proteomics), as well as metabolomics, transcriptomics and complex intercellular communication biosignals. All of these are analyzed in real-time within the same sample and show the flexibility that graphene can bring to biosensing (and sensing in general).
BPU graphene platform from Cardea
The BPU platform is used in the original cancer detection devices and is set to be used in the soon-to-be-developed electronic nose. The BPU is essential for both the cancer diagnostic platform and the recently announced electronic nose, and is being developed as a central device that can be adapted for different applications and clinical scenarios.
The BPU platform consists of a number of key components and is essentially a microprocessor that converts a biological signal into an electrical signal. Like any sensing device, the BPU has computing hardware that houses a touch reader and analyzer to convert any output from the touch surface into detectable and usable output for the user. In terms of the actual sensing part of the platform, there are two key components: the graphene layer and the trapping molecules.
The graphene layer, which is used as a field-effect transistor (gFET), is used to directly convert various biological signals into digital information. Graphene is widely used as a sensing platform in various industries because it has a high active surface area where functional sensing groups can be attached, but it also has high electrical conductivity and charge carrier mobility. This makes graphene sensitive to any localized changes, as the binding of any biomolecules (or any stimulus for that matter) changes the conductivity in the graphene sheet.
On top of the graphene layer are various trapping molecules. A gFET combined with a biosensing group results in a graphene sensing platform that is semiconducting in nature. So when a biomolecule binds to the surface, it changes the electrical properties of the graphene and generates a detectable signal that can be used in a readable output. Many different capture molecules (to bind to specific biomarkers) can be placed on the gFET layer, so it is possible to detect RNA, DNA and protein-based biomolecules on a single platform. The system is therefore adaptable to both cancer diagnosis and disease detection.
The small size of graphene (both in terms of its thinness and its lateral dimensions) means that a number of gFETs can be placed side by side on a single chip, extending the sensor’s biosignal range and bandwidth. Primarily, this small scale, together with the sensing efficiency of graphene, enables a flexible and sensitive detection platform.
Using the BPU platform as an electronic nose
The development of Cardea’s electronic nose has just been announced, but it builds on the success of cancer detection platform she had The goal is to use the same graphene BPU platform in the company’s electronic nose, similar to cancer diagnostic devices. As described above, the ability to create small and customizable gFETs means that the process of customizing the platform to infectious diseases should be relatively straightforward, provided it is easy to attach the relevant capture molecules onto the graphene layer.
The BPU technology has already shown that it can be produced at scale, as Cardea already has the capacity to produce thousands of units. The target market is infectious disease detection in developing countries, as compared to other diagnostic platforms, the ability to detect a range of infectious diseases helps reduce development time and cost, making it more attractive to markets that they cannot afford to spend so much money on medical devices. And it opens the doors to communities that have traditionally been underserved when it comes to medical testing.
As mentioned above, the use of graphene in the detection mechanism helps to increase the sensitivity of the platform, so much so that it has been demonstrated that these new BPU-based platforms can detect if someone has an infectious disease through their breath. The aim of the funded project is to test the ability of BPU functionalized with an insect odor receptor to detect agonistic odorants (agonistic odorants are substances that initiate a response with a receptor).
The electronic nose under development has the potential to detect a number of diseases including Covid and malaria and can also be used to detect various types of cancer like its predecessor. It is believed that platforms based on aroma sensing can be used in a wide range of applications, from clinical healthcare settings to environmental monitoring, agriculture and biosecurity applications. The flexibility of the BPU may mean that the platforms can be used even more widely in the future once this project is completed and in real-world use.