Research On Accumulation And Sensing Of PAHs Exposure Biomarkers Based On Graphene

Polycyclic aromatic hydrocarbon(PAHs) is a hydrophobic hydrocarbon with its molecular structure containing two or more benzene ring, and it is a persistent organic pollutant which has carcinogenic, mutagenic and teratogenic effects and widely exists in the environment. PAHs is an important kind of food pollutants, which can enter the food chain by environmental medium. It is a potential and enormous threat to human health if a person eats PAHs contaminated food for a long time, so it is a significant study of PAHs exposure level of crowd dietary sources. The PAHs intake in human body can be estimated through the determination of PAHs exposure biomarkers, which can provide reference for human PAHs exposure level and health risk assessment, adjust the way of cooking and daily diet, and reduce or avoid the harm of PAHs. Graphene is a two-dimensional carbon nano material with excellent electric conductivity, large specific surface area and enormous π-π conjugate system, and it is often used as absorbent and electrode modified material. In this paper, we committed to develop modified electrodes on the basis of graphene, applied to the preconcentration and sensing of PAHs exposure biomarkers 1-hydroxypyrene(1-OHP), α-naphthol(α-N) and β-naphthol(β-N). Electrochemical reduced graphene oxide modified electrode and GR and AQ layer-by-layer self-assembly modified electrode were established and characterized, at which the electrochemical behaviors of 1-OHP, α-N and β-N were investigated. The conditions of the fabrication of modified electrodes, electrochemical measurements and mechanisms were studied, and new approaches were developed for the preconcentration in situ and sensing of 1-OHP, α-N and β-N. The details are shown as follows:(1) A novel method was constructed for the simultaneous preconcentration and determination of naphthol isomers(α-N and β-N) at electrochemical reduced graphene oxide modified electrode(E-r GO/GCE). Electrochemical reduction method was employed for the fabrication of E-r GO/GCE, and it was characterized by scanning electron microscope, raman spectroscopy and infrared spectroscopy. The results showed that the morphology of E-r GO/GCE was a porous three-dimensional structure and its electrical conductivity was good. The electrochemical behaviors of naphthol isomers were explored at E-r GO/GCE by cyclic voltammetry(CV) and differential pulse voltammetry(DPV). The results showed that α-N and β-N were an irreversible electrochemical process at E-r GO/GCE with a pair of completely separated oxidation peaks. The CV response currents of α-N and β-N at E-r GO/GCE were 11.28 and 8.57 times stronger than that at bare GCE, respectively. The optimal conditions for α-N and β-N detection were p H 6.0 PBS, 250 s GO electrochemical-reduced time, +0.1 V accumulation potential and 90 s accumulation time. Good linear relationships between the concentration of α-N and its DPV response current were observed in the range of 5~400 n M and 0.5~20 μM, and good linear relationships between the concentration of β-N and its DPV response current were observed in the range of 5~350 n M and 0.5~20 μM. The detection limits of α-N and β-N were 1.01 n M and 0.43 n M(S/N=3), and sensitivity were 0.0097 μA/n M and 0.0113 μA/n M, respectively. The method was used to measure naphthol isomers in real human urine samples, and its results were close to the datas of HPLC method for naphthol isomers determination in human urine.(2) A fast and sensitive DPV approach was developed for the preconcentration and in situ detection of 1-OHP. Electrochemical reduction method was employed for the fabrication of E-r GO/GCE, and the preconcentration of 1-OHP was enriched by synergetic accumulation and π-π conjugate accumulation. The optimal conditions for 1-OHP detection were p H 2.0 PBS, 300 s GO electrochemical-reduced time, 600 s preconcentrate time. A good linear relationship between the concentration of 1-OHP and its DPV response current was obtained in the range of 5~300 n M with a limit of detection of 0.84 n M(S/N=3) and a sensitivity of 0.1684 μA/n M. It was successfully applied to the determination of 1-OHP in real human urine samples with recoveries of 97.3%~101.1%, and its results were similar to the datas of HPLC method for 1-OHP determination in human urine.(3) The {GR-AQ}n modified electrode was prepared by layer-by-layer(LBL) self-assembly of GR and AQ through π-π conjugate action on the basis of electrochemical reduced graphene oxide. The UV-vis spectroscopy and CV were used for characterizing the LBL self-assembly process of {GR-AQ}n. The electrochemical behavior of 1-OHP was studied at {GR-AQ}n /GCE, and its result demonstrated that the reaction was a reversible and adsorption-controlled electrochemical process at the modified electrode. The optimal conditions for {GR-AQ}n /GCE fabrication were 100 s GO electrochemical-reduced time, 1 mg/m L GR, 0.5 mg/m L AQ, 16 layer number, and the optimal conditions for 1-OHP determination were p H 2.0 PBS, +0.8 V accumulation potential, 400 s accumulation time. A good linear relationship between the concentration of 1-OHP and its DPV response current was obtained in the range of 0.5~120 n M, and the detection limit(S/N=3) and sensitivity were 0.07 n M and 0.5539 μA/n M, respectively. The method was applied for the detection of 1-OHP in real human urine, with its results close to the datas of HPLC method for 1-OHP determination in human urine.