Simultaneous Determination of Four DNA bases at Graphene Oxide/Multi-Walled Carbon Nanotube Nanocomposite-Modified Electrode

Abstract

In this study, we developed a modified glassy carbon electrode (GCE) with graphene oxide, multi-walled carbon nanotube hybrid nanocomposite in chitosan (GCE/GO-MWCNT-CHT) to achieve simultaneous detection of four nucleobases (i.e., guanine (G), adenine (A), thymine (T) and cytosine (C)) along with uric acid (UA) as an internal standard. The nanocomposite was characterized using TEM and FT-IR. The linearity ranges were up to 151.0, 78.0, 79.5, 227.5, and 162.5 µM with a detection limit of 0.15, 0.12, 0.44, 4.02, 4.0, and 3.30 µM for UA, G, A, T, and C, respectively. Compared to a bare GCE, the nanocomposite-modified GCE demonstrated a large enhancement (~36.6%) of the electrochemical active surface area. Through chronoamperometric studies, the diffusion coefficients (D), standard catalytic rate constant (K_s), and heterogenous rate constant (K_h) were calculated for the analytes. Moreover, the nanocomposite-modified electrode was used for simultaneous detection in human serum, human saliva, and artificial saliva samples with recovery values ranging from 95% to 105%.

Keywords: adenine; cytosine; graphene oxide; guanine; multi-walled carbon nanotube; nanocomposite; thymine; uric acid; voltammetry.

Scheme 1

Diagram for the preparation of graphene oxide, multi-walled carbon nanotube (GO-MWCNT) hybrid nanocomposite and the modification of glassy carbon electrode (GCE) surface.

Figure 1

TEM images for the GO-MWCNT nanocomposites in CHT which were used for the modification of GCE surface (scale bars for image (A) to (B) are 1.0 and 0.5 μm).

Figure 2

FT-IR spectra for MWCNT, GO, CHT and GO-MWCNT hybrid nanocomposite in CHT.

Figure 3

DPV voltammograms using GCE/GO-MWCNT-CHT for pH effect on the simultaneous electrochemical detection of four DNA bases in the presence of UA (pH range: 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 7.4, and 8.1).

Figure 4

Relationship between pH and E_p for the simultaneous electrochemical detection of all four DNA bases in the presence of UA using GCE/GO-MWCNT-CHT.

Scheme 2

Electrochemical oxidation mechanisms of UA and DNA bases as determined from our experimental data and literature.

Figure 5

(A) Comparison of CV using bare GCE, GCE/CHT, and the GCE/GO-MWCNT-CHT to detect 175 µM UA, 50 µM G, 50 µM A, 250 µM T, and 250 µM C in 0.2 M PBS (pH 7.0); (B) comparison of DPV using bare GCE, GCE/CHT, and the GCE/GO-MWCNT-CHT to detect 15 µM UA, 15 µM G, 15 µM A, 35 µM T, and 35 µM C in 0.2 M PBS (pH 7.0).

Figure 6

Overlay of DPV measurements using GCE/GO-MWCNT-CHT for individual detections and simultaneous detection of 12.5, 147.5, 97.5, and 10 μM of A, T, C, and G in 0.2 M PBS (pH 7.0).

Figure 7

Calibration curves based on DPV for simultaneous detection of UA, G, A, T, and C using GCE/GO-MWCNT-CHT with concentrations ranging from 1.0–151.0, 1.0-78.0, 1.0-79.5, 5.0-267.5, and 12.5–182.5 µM for UA, G, A, T, and C, respectively. The lowest end of the dynamic ranges started from the blue curve and ended in the purple curve for the highest.

Figure 8

Calibration graphs for UA (A) and all four nucleobases (B–E), respectively.

Figure 9

Linear dependence of i_p on v for bare GCE and GCE/GO-MWCNT-CHT.

Figure 10

(A) Chronoamperograms of GCE/GO-MWCNT-CHT for varying concentrations of adenine (A): 25, 50, and 150 μM in 0.2 M PBS (pH 7.0); (B) plots of anodic peak currents (I_pa) versus t^−1/2; (C) plot of the slope of the straight line versus concentration of A.