Label-free capacitive immunosensor for microcystin-LR using self-assembled thiourea monolayer incorporated with Ag nanoparticles on gold electrode

A label-free immunosensor based on a modified gold electrode incorporated with silver(Ag) nanoparticles (NPs) to enhance the capacitive response to microcystin-LR (MCLR) has been developed Anti-microcystin-LR (anti-MCLR) was immobilized on silver nanoparticles bound to a self-assembled thiourea monolayer Interaction ofanti-MCLR and MCLR were directly detected by capacitance measurement. Under optimum conditions, MCLR could be determined with a detection limit of 7.0 pg l(-1) and linearity between 10 pg l(-1) and 1 mu g l(-1). The immobilized anti-MUR oil self-assembled thiourea monolayer incorporated with silver nanoparticles was stable and good reproducibility of the signal could be obtained up to 43 times with an R.S.D. of 2.1%. Comparing to the modified electrode without silver nanoparticles it gave 1.7-fold higher sensitivity and lower limit of detection. The developed immunosensor was applied to analyze MCLR in water samples and the results were in good agreement with those obtained by high-performance liquid chromatography (HPLC) (P < 0.05). (C) 2008 Elsevier B.V. All rights reserved.