Label-free immunosensing of microcystin-LR using a gold electrode modified with gold nanoparticles

The hepatotoxic microcystins, especially microcystin-LR (MC-LR), are causing serious problems to public health and fisheries. We describe here a label-free amperometric immunosensor for rapid determination of MC-LR in water sample. The sensor was prepared by immobilizing antibody on a gold electrode coated with L-cysteine-modified gold nanoparticles. The stepwise self-assembly of the immunosensor was monitored and characterized by means of electrochemical impedance spectroscopy and differential pulse voltammetry. A 0.60 mmol L(-1) solution of hydroquinone was used as the electron mediator. The immunosensor was incubated with MC-LR at 25 A degrees C for 20 min, upon which the differential pulse voltammetric current changed linearly over the concentration range from 0.05 to 15.00 mu g L(-1), with a detection limit of 20 ng L(-1). The developed biosensor was used to determine MC-LR in spiked crude algae samples. The recovery was in the range from 95.6 to 105%. This method is simple, economical and efficient, this making it potentially suitable for field analysis of MC-LR in crude algae and water samples.