Abstract

The electrochemical sensors have an essential role in the detection of amino acids which has clinical uses as a biomarker for a wide range of diseases. In this paper, the dopamine-functionalized graphene oxide was used to develop a screen printed electrochemical sensor (DA-GO/SPE). This sensing platform was used for simultaneous detection of homocysteine and folic acid. An efficient strategy was used for immobilization of dopamine on graphene oxide sheets based on NH2 group of dopamine with the COOH group of GO using the EDC/NHS reaction. The electrochemical investigation of prepared sensing platform confirmed that the DA-GO composite shows excellent catalytic activity toward homocysteine based on EC? mechanism. A pair of redox peaks with one anodic peak (Ep = 220 mV), which related to the oxidation of DA to its quinone structure and one cathodic peak (Ep = 160 mV) was obtained at the DA-GO modified SPE. The values of ? and ks for DA at the DA-GO/SPE were calculated to be 0.45 and 2.32 s-1, respectively. The DA-GO/SEP shows good catalytic response toward homocysteine and folic acid with a linear range of 0.5?900 ?M and 1.0?260 ?M, respectively. The limit of detection of 0.15 ?M and 0.32 ?M were obtained for homocysteine and folic acid, respectively (S/N = 3). Moreover, the RSD of three measurements using DA-GO/SPE was 1.9, indicating good repeatability.