ULTRA-SENSITIVE GRAPHENE NANO-BIOSENSORS

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Illnesses like cancer, cardiovascular diseases, Alzheimer's, Parkinson's, and diabetes have negative effects on patients, society and insurance systems. The ever-ageing population has a critical demand for more efficient, affordable healthcare.Nanotechnology is building nanometre sized devices for electronics and medical applications, raising expectations for better diagnostics and 'smart' treatments. Nanosensors could identify disease biomarkers at the earliest possible stage, potentially intercepting more serious illness. Available therapeutic options informed by early detection are greatly enhanced e.g. prostate cancer, the 2nd largest killer of male cancer patients, better than 70% chance of successful treatment if detected early. Biomarkers are often present at very low concentrations. Monitoring of biomarkers like prostate-specific-antigen, glucose or other blood-based markers at clinical concentrations - possible using nano-sensor arrays - could provide genuine benefits to patients. Non-invasive smart-testing using urine or breath samples would have a hugely beneficial impact on chronic patients and for monitoring biomarker levels after treatment. Current diagnosis of disease biomarkers is based on detection of fluorescently labeled probe molecules which interact with specific substrate-bound receptors. This is expensive and time-consuming, with limited sensitivity. Nanoscale electrochemical biosensors can achieve much higher sensitivities, using label-free biomarkers. We will exploit our recent advances in graphene growth and semiconductor surface functionalisation, to develop wafer-based, graphene/Silicon Carbide (SiC) technology for novel biosensor applications. Graphene, a single atomic layer of graphite, has some exceptional electronic properties such as its zero bandgap and very high carrier mobilities at room temperature - similar to carbon nanotubes. Graphene can be grown on SiC substrates using silicon sublimation. The principal advantage of graphene/SiC over conventional graphene - from exfoliation of graphene flakes from graphite substrates - is the capacity for graphene growth on flat, large-area wafers (up to 100mm in diameter), on which devices can subsequently be fabricated using standard semiconductor processing. Nano-channel graphene electronic devices will be fabricated on SiC substrates. We have shown that graphene can be bio-functionalized and will use surface functionalisation chemistry to attach bio-receptors to nano-channel graphene devices. Because of their high surface/volume ratio and quantum confinement properties, the electrical properties of graphene nano-channels have increased signal/noise ratios and are strongly influenced by minor perturbations, enabling biomarker detection at ultra-sensitive (fM) analyte levels. Current transport through the nanosensor should show extreme sensitivity to its local environment.A proof-of-concept nano-channel bio-sensor will be developed using antibody-functionalized graphene, capable of specific and selective interaction with the target prostate cancer biomarker, 8-hydroxydeoxyguanosine (8-OHdG). When the bio-molecule binds to the functionalised surface, it produces an electrical signal, which can be detected. The key to an effective biosensor is that only specific bio-molecules will bind to the receptor and produce a response. Selectivity can be controlled by choosing the correct bio-receptor.The functionalisation chemistry proposed allows for attachment of a variety of antibody, enzyme, or aminoacid bio-receptors. Our graphene/SiC biochip could eventually provide an ultra-sensitive, fast-diagnosis, cost-effective test for numerous disease biomarkers - potentially revolutionizing healthcare by bringing diagnosis and monitoring to the point-of-care. Once trialed, mobile monitoring systems, transmitting a signal to a hand held readout display, could allow translation of healthcare from hospitals to patients in their own homes.