SPIRIT: A Portable Biosensor for the Early Detection of Harmful Algal Blooms.

Marine dinoflagellates of the genus Alexandrium can produce dangerous amounts of toxins responsible for paralytic shellfish poisoning (PSP) at such low cell densities that water discoloration often associated with Harmful Algal Blooms (HABs) is not always evident. Species that produce toxins are difficult to distinguish from non-toxic species, and current identification methods are expensive, time-consuming, and require special training. Development of a rapid, low-cost and easy-to-use device to detect and monitor Alexandrium in the field would be an important advancement for coastal managers and the shellfish industry, as HABs vary interannually in location, intensity, and duration. We are developing a portable biosensor based on RNA detection. This method uses molecular probes and surface plasmon resonance (SPR), a label-free optical method for the detection of Alexandrium tamarense and A. ostenfeldii, two species of Alexandrium commonly found in the Gulf of Maine. Previously we have shown that this method can reliably discriminate between synthetic DNA sequences designed to mimic each species. Using RNA extracted from cultured Alexandrium, we have also confirmed the specificity of the probes to detect only the species targeted with no cross-reactivity with other probes. To validate the performance of this custom-built instrument we have conducted comparison assays on a second, commercially available SPR instrument, the industry-standard Biacore Q, and we found our instrument to be more sensitive than the Biacore. These results show great promise for the use of this technology as a way to quickly and more effectively detect and monitor HABs at shellfish harvesting sites.