Rapid microcystin-LR detection using antibody-based electrochemical biosensors with a simplified calibration curve approach

Harmful algal blooms (HABs) can release cyanotoxins such as microcystins (MCs), especially, microcystin-leucine-arginine (MC-LR) which is one of the commonest and most toxic, into our water bodies and can lead to several acute or chronic diseases such as liver diseases and respiratory irritation in humans. There is an increasing need for rapid and simple detection of MC-LR in water bodies for early warning of HABs. In this study, we developed an innovative on-site screening electrochemical impedance spectroscopy (EIS) biosensor with a simplified calibration curve that can rapidly detect blooms for early action in similar water bodies. The novel aspect of this research is that various chemical cleaning procedures and surface modifications were evaluated to improve the antibody-embedded electrochemical sensor performance. In addition, a simplified calibration curve was constructed from different water samples to reduce the need for frequent recalibration in practical applications. In this study, two distinct commercially available screen-printed carbon electrodes (SPCEs) were modified as a cost-effective substrate for MC-LR biosensing with anti-MC-LR/MC-LR/cysteamine-coating. The study showed that an appropriate cleaning procedure might minimize the sensor performance difference after each electrode modification. The biosensor showed excellent sensitivity toward MC-LR detection in lake water samples with a limit of detection (LOD) of 0.34 ngL^-1. The simplified calibration curve was developed and used to predict unknown MC-LR concentrations in several lake water samples with a relative standard deviation (RSD) of 1.0-4.4% and a recovery of 75-112%, indicating the suitability of the developed biosensor and a streamlined calibration curve for rapid MC-LR measurements for different water bodies with similar water quality. This approach can therefore reduce the need for frequent calibration efforts and can be employed as the first line of testing for MC-LR in drinking and recreational water sources, especially in emergencies.