Carbon Nanotubes Biosensor For The Determination Of Microcystins In Water

Microcystin-LR (MC-LR), what released by cyanbacteria, is kind of cyclic heptapeptides, MC-LR may cause structural and functional disturbance of liver. As the process of industrialization is speeding up, there are a large number of nitrogen and phosphorus pollutants in water, Microcystin-LR (MC-LR) release during eutrophication. MC-LR becomes an important element in water quality control and environmental monitoring. The maximum limit for MC-LR in drinking water is1μg·L-1which was provided by the World Health Organization (WHO). There are many analytical techniques which were used for MC-LR determination, but these methods are high cost, complicated and need most researchers, so we must find a method with high sensitivity and simple operation. Electrochemical immunoassay is a kind of determination method that combined with immunoreactions and electrochemical analysis.CNTs have unique electrical, optical, thermal, and mechanical properties, especially, because of their good conductivity CNT become the subject of many studies. The electrochemical immunosensor which modified carbon nanotubes (CNTs) has the advantages of high sensitive, fast response, and good selectivity.In this study, we use electrochemical immunosensor which modified carbon nanotubes (CNTs) for the detection of microcystin-LR (MC-LR). Differential pulse voltammetry (DPV) and cyclic voltammetry (CV) were used to research the redox mechanism on the surface of electrochemical immunosensor, and optimize the determination conditions of MC-LR. The major results were below:optimal conditions is that modified dose is12μL, pH was7.4, temperature is37℃.Under optimal conditions, the electrochemical immunosensor which modified carbon nanotubes (CNTs) has a good electrochemical behavior and a lower detection limit which was down to10-6μg?L, the linear relationship between ΔI and concentration of MC-LR was obtained in the range of10-5～1μg?L, the linear equation was Δi(le-5A)=1.016logC(μg?L-1)+5.85(MWCNT-OH) and Δi(le-5A)=0.1014logC(μg?L-1)+0.6048(SWCNT-COOH);This modified electrochemical immunosensor exhibited good reproducibility and good stability for the detection of microcystin-LR(MC-LR). The recovery is88%-108%when using this immunosensor to measured natural water sample;Comparison with Multi-Walled Carbon Nanotubes(MWCNT)/Single-walled carbon nanotubes (SWCNT) and hydroxy multi-walled carbon nanotubes (MWCNT-OH)/carboxyl single-walled crabon nanotubes(SWCNT-COOH), the result showed that the electrochemical immunosensor which modified hydroxy multi-walled carbon nanotubes(MWCNT-OH)/carboxyl single-walled crabon nanotubes (SWCNT-COOH) have high sensitivity;The electrochemical kinetics of the modified electrochemical immunosensor was investigated, the Michaelis constant of enzymatic reaction was0.87mmol?L-1.