Part-per-trillion level detection of microcystin-LR using a periodic nanostructure

Accelerated eutrophication of surface water sources has resulted in an increased presence of cyanobacterial blooms in fresh water. The release of hepatotoxins like microcystins from such blooms can have a catastrophic impact on local human and wildlife ecosystems. Therefore, a rapid, low-cost, reliable, and highly sensitive method for low-concentration detection of microcystins is needed to minimize risks to public health. In this paper, we report the first experimental demonstration of microcystin-leucine-arginine (MC-LR) detection in water at low part-per-trillion levels using a portable optical sensor. The demonstrated biosensor utilizes a highly sensitive electromagnetic surface wave in periodically coupled artificial nanostructures to directly probe the interaction between immobilized antibodies and MC-LR. The surface customization reported here uses a layer-by-layer polyelectrolyte adsorption process to provide highly stable and site-directed immobilization of target antibodies. Steady-state analysis of the sensor's response confirms that the plasmonic sensor can detect the presence of MC-LR antigens at part-per-trillion levels. The demonstrated sensor is an important first step toward realizing a lab-on-a-chip sensing system for in situ, autonomous, real-time, distributed environmental monitoring of MC levels in drinking water.