Characterization of an ultrasensitive biosensor based on a nano-Au/DNA/nano-Au/poly(SFR) composite and its application in the simultaneous determination of dopamine, uric acid, guanine, and adenine

An ultrasensitive method for the simultaneous determination of dopamine (DA), uric acid (UA), guanine (G), and adenine (A) was developed using differential pulse voltammetry with a three-dimensionally distributed Au nanoparticle (GNP)-modified glassy carbon electrode (GCE). The nano-Au/DNA/nano-Au/poly(SFR)/GCE microstructure was characterized by scanning electron microscopy, electrochemical impedance spectroscopy, and atomic force microscopy, showing an anchored three-dimensional distribution of GNPs on the modified electrode. The electrode exhibited ultrasensitive responses to DA, UA, G, and A due to poly(SFR) electrocatalytic activities and the large surface area of the GNPs. All four analytes showed well-defined catalytic oxidation peaks at the modified electrode. DA, UA, G, and A yielded linear ranges from 8.0 × 10−9 M to 1.1 × 10−6 M, 9.0 × 10−8 M to 1.2 × 10−5 M, 9.0 × 10−9 M to 5.0 × 10−6 M, and 6.0 × 10−8 M to 8.0 × 10−7 M, respectively, and detection limits for the analytes were 2.0 × 10−10 M, 8.0 × 10−9 M, 5.0 × 10−10 M, and 4.0 × 10−9 M, respectively. The feasibility of the proposed assay for use in human serum and urine was investigated and satisfying results were obtained.