Attaining Attomolar Detection and Long Target Capture of Single Strand DNA with Graphene Biosensors

Nucleic acids often behave as biomarkers for various ailments, such as cancer, where a particular strand will upregulate as an indication of the presence of the disease. The need to develop a process for detection of nucleic acids in low concentrations is pressing for the purpose of early cancer screening. Furthermore, detecting a long nucleic acid with a short nucleic acid probe also serves as a step towards early cancer diagnostics, as nucleic acids in human plasma are thousands of nucleotides in length. Here, we describe the approach for fabricating scalable graphene field effect transistors (GFETs) for detection of ssDNA down to attomolar concentrations in addition to detecting a long target with a shorter probe. Graphene was grown via chemical vapor deposition in-lab and transferred through an electrolysis bubbling technique with Raman spectroscopy to determine the quality of the graphene and atomic force microscopy to verify the presence of linker and probe molecule attachment. Data was collected via an all-electronic readout method by characterizing the shift in the Dirac voltage of the GFETs, which exhibits Hill-Langmuir behavior for varying concentrations of the target. Our results show potential for eventual early disease diagnostics in complex fluids.