Graphene Field-effect Transistor Biosensor Research Articles

Real-Time Monitoring of Nitric Oxide at Single-Cell Level with Porphyrin-Functionalized Graphene Field-Effect Transistor Biosensor.

An ultrasensitive and highly efficient assay for real-time monitoring of nitric oxide (NO) at single-cell level based on a reduced graphene oxide (RGO) and iron-porphyrin-functionalized graphene (FGPCs) field-effect transistor (FET) biosensor is reported. A layer-to-layer assembly of RGO and FGPCs on a prefabricated FET sensor surface through π-π stacking interaction allowed superior electrical conductivity caused by RGO, and highly catalytic specificity induced by metalloporphyrin, ensuring the ultrasensitive and highly specific detection of NO. The results demonstrated that the RGO/FGPCs FET biosensor was capable of real-time monitoring of NO in the range from 1 pM to 100 nM with the limit of detection as low as 1 pM in phosphate-buffered saline (PBS) and 10 pM in the cell medium, respectively. Moreover, the developed biosensor could be used for real-time monitoring of NO released from human umbilical vein endothelial cells (HUVECs) at single-cell level. Along with its miniaturized sizes, ultrasensitive characteristics, and fast response, the FET biosensor is promising as a new platform for potential biological and diagnostic applications.

Fully integrated graphene electronic biosensor for label-free detection of lead (II) ion based on G-quadruplex structure-switching

This work presents a fully integrated graphene field-effect transistor (GFET) biosensor for the label-free detection of lead ions (Pb2+) in aqueous-media, which first implements the G-quadruplex structure-switching biosensing principle in graphene nanoelectronics. We experimentally illustrate the biomolecular interplay that G-rich DNA single-strands with one-end confined on graphene surface can specifically interact with Pb2+ ions and switch into G-quadruplex structures. Since the structure-switching of electrically charged DNA strands can disrupt the charge distribution in the vicinity of graphene surface, the carrier equilibrium in graphene sheet might be altered, and manifested by the conductivity variation of GFET. The experimental data and theoretical analysis show that our devices are capable of the label-free and specific quantification of Pb2+ with a detection limit down to 163.7ng/L. These results first verify the signaling principle competency of G-quadruplex structure-switching in graphene electronic biosensors. Combining with the advantages of the compact device structure and convenient electrical signal, a label-free GFET biosensor for Pb2+ monitoring is enabled with promising application potential.

Fabrication of Ultrasensitive Field-Effect Transistor DNA Biosensors by a Directional Transfer Technique Based on CVD-Grown Graphene

Most graphene field-effect transistor (G-FET) biosensors are fabricated through a routine process, in which graphene is transferred onto a Si/SiO2 substrate and then devices are subsequently produced by micromanufacture processes. However, such a fabrication approach can introduce contamination onto the graphene surface during the lithographic process, resulting in interference for the subsequent biosensing. In this work, we have developed a novel directional transfer technique to fabricate G-FET biosensors based on chemical-vapor-deposition- (CVD-) grown single-layer graphene (SLG) and applied this biosensor for the sensitive detection of DNA. A FET device with six individual array sensors was first fabricated, and SLG obtained by the CVD-growth method was transferred onto the sensor surface in a directional manner. Afterward, peptide nucleic acid (PNA) was covalently immobilized on the graphene surface, and DNA detection was realized by applying specific target DNA to the PNA-functionalized G-FET biosensor. The developed G-FET biosensor was able to detect target DNA at concentrations as low as 10 fM, which is 1 order of magnitude lower than those reported in a previous work. In addition, the biosensor was capable of distinguishing the complementary DNA from one-base-mismatched DNA and noncomplementary DNA. The directional transfer technique for the fabrication of G-FET biosensors is simple, and the as-constructed G-FET DNA biosensor shows ultrasensitivity and high specificity, indicating its potential application in disease diagnostics as a point-of-care tool.

Gold nanoparticles-decorated graphene field-effect transistor biosensor for femtomolar MicroRNA detection.

Early detection is proven to be the best chance for successful cancer treatment. MiRNAs, as ideal biomarkers, can identify cancer in the early stage. Therefore, development of highly sensitive and selective detection methods for miRNA is still anticipated. Here we report on a gold nanoparticles (AuNPs)-decorated graphene field-effect transistor (FET) biosensor for highly sensitive, selective and label-free detection of miRNA. The AuNPs-decorated graphene FET biosensor was fabricated by drop-casting the reduced graphene oxide (R-GO) suspension onto the sensor surface, and subsequently decorating AuNPs onto the surface of R-GO. After peptide nucleic acid (PNA) probe was immobilized on the AuNPs surface, miRNA detection was carried out via PNA-miRNA hybridization. It was found that the developed FET biosensor was able to achieve a detection limit as low as 10 fM. In addition, the biosensor enabled an accurate distinction of complementary miRNA from one-base mismatched miRNA and noncomplementary miRNA. What's more, this highly sensitive and selective assay was also applied to the detection of miRNA in serum samples, making it a potential method for diagnosis of gene-related diseases.

Scalable graphene field-effect sensors for specific protein detection

We demonstrate that micron-scale graphene field-effect transistor biosensors can be fabricated in a scalable fashion from large-area chemical vapor deposition derived graphene. We electrically detect the real-time binding and unbinding of a protein biomarker, thrombin, to and from aptamer-coated graphene surfaces. Our sensors have low background noise and high transconductance, comparable to exfoliated graphene devices. The devices are reusable and have a shelf-life greater than one week.