Scalable Production of High-Sensitivity, Label-Free DNA Biosensors Based on Back-Gated Graphene Field Effect Transistors

Abstract

Scalable production of all-electronic DNA biosensors with high sensitivity and selectivity is a critical enabling step for research and applications associated with detection of DNA hybridization. We have developed a scalable and very reproducible (>90% yield) fabrication process for label-free DNA biosensors based upon graphene field effect transistors (GFETs) functionalized with single-stranded probe DNA. The shift of the GFET sensor Dirac point voltage varied systematically with the concentration of target DNA. The biosensors demonstrated a broad analytical range and limit of detection of 1 fM for 60-mer DNA oligonucleotide. In control experiments with mismatched DNA oligomers, the impact of the mismatch position on the DNA hybridization strength was confirmed. This class of highly sensitive DNA biosensors offers the prospect of detection of DNA hybridization and sequencing in a rapid, inexpensive, and accurate way.

Keywords: DNA biosensors; field effect transistors; graphene; hybridization; scalable.

Figure 1

(a) Schematic of DNA biosensor based upon a graphene field effect transistor functionalized with complementary probe DNA. (b) Raman spectrum of the channel region of a graphene field effect transistor (GFET) after processing. Inset: Optical micrograph of an array of 52 GFETs. (c) I–V_g characteristics for an array of 52 GFET devices showing excellent reproducibility. (d) Histogram of the Dirac voltage extracted from the I–V_g characteristics of panel (b) along with a Gaussian fit to the data (red curve).

Figure 2

(a) AFM line scans of (1) annealed graphene, (2) PBASE-functionalized graphene, and (3) graphene functionalized with PBASE and aminated DNA. Inset: AFM images showing the scan lines plotted in the main figure. Scan lines are 2.5 μm. Z-scale 8 μm. (b) I–V_g characteristics for a typical GFET that was annealed, functionalized with PBASE, reacted with 22-mer aminated probe DNA, and exposed to 10 nM target DNA in deionized water.

Figure 3

(a) Relative Dirac voltage shift as a function of concentration for DNA targets of different lengths. Error bars (standard deviation of the mean) are approximately equal to the size of the plotted point. Solid curves are fits to the data based on the Sips model. (b) Variation of the fit parameters A (red data) and K_A (blue data) in eq 1 with DNA oligomer length. The red and blue lines are fits to the data, as discussed in the main text.

Figure 4

Relative response of GFET-based 22-mer DNA biosensors to the target sequence and various controls, all at a concentration of 1 μM. The base sequences of the oligomers tested are listed, with mismatches shown in red. Starting from the bottom, the oligomers tested are target DNA, single mismatch at the 5′ end, single mismatch at the center, two mismatches at the 5′ end and the center, and random sequence DNA. Error bars are standard deviation of the mean.