On-site microfluidic aptasensor for rapid and highly selective detection of microcystin-LR.

To detect microcystin-LR (MC-LR), a potent cyanotoxin harmful to human health, fast and precise monitoring tools are essential, particularly for on-site applications. In this study, we developed a novel on-site microfluidic aptasensor system that utilizes a fluorescence-tagged aptamer for the rapid and selective detection of MC-LR. By employing a target non-immobilized aptamer selection technique, high-affinity DNA aptamers for MC-LR were identified, and then further optimized through sequence truncation to enhance detection efficiency. The developed aptamer was designed such that its fluorescence is quenched in the absence of MC-LR, but recovered in its presence, enabling a clear signal detection that correlates with a toxin concentration. The developed system achieved a detection limit of 1.9 ppb, significantly lower than the safety threshold suggested by world health organization (WHO) for recreational waters, demonstrating sufficient sensitivity for reliable on-site monitoring. In addition, the microfluidic aptasensor system demonstrated high specificity, exhibiting the strongest response to MC-LR compared to other cyanotoxins. This system is the first portable MC-LR detection tool that allows for on-site environmental monitoring with the advantages of its fast response time and ease of operation. Combining a low detection limit with high accuracy, the microfluidic aptasensor system presents a promising alternative to conventional laboratory-based methods, providing a practical and reliable solution for water quality assessment.