A simple and low-cost disposable biosensor to determine microcystin-LR in urban natural waters

Toxic cyanobacteria pose a serious threat to public health due to production of cyanotoxins, especially microcystin LR (MC-LR), which is released in water upon cell death. In humans, microcystin causes damage to the liver, affects the kidneys and is a risk to the gastrointestinal tract. In this work, MC-LR was detected using a biosensor based on alkaline phosphatase physically adsorbed on a carbon-printed electrode. The measurements were performed before and after the addition of MC-LR. The device gave linear response for a concentration range between 11 and 100 ng.L−1, in addition to high selectivity , with a limit of detection of 1.3 ng.L−1 and a limit of quantification of 4.5 ng.L−1. High accuracy was obtained, with a low relative error of 3.9% when used to quantify MC-LR in natural water. These results suggest a simple and low-cost alternative to determine if MC-LR is present in urban waters that undergo eutrophication due to high nutrient loads.