Harmful algal blooms (HABs) are an ongoing ecological concern for waterways across the globe.  Waterways are impacted during bloom events when odors are released, dead zones are formed in the water column, and dangerous toxins (cyanotoxins) are released into the ecosystem. These cyanotoxins such as microcystin, anatoxin-a, saxitoxin, cylindrospermopsin, and nodularian are known to cause neurotoxicity, hepatotoxicity, cytotoxicity, and endotoxicity. To effectively manage HABs, the ability to rapidly detect the presence and concentration of cyanotoxins in real time needs to be implemented. Current analytical methods for identification of cyanotoxins are based on complex, time consuming procedures. In the current literature, aptamers have been successfully developed to identify a range of compounds such as proteins, metals, and small molecules. To overcome the barriers found in existing sensing platforms, this work focused on development of a rapid, field-deployable quartz crystal microbalance (QCM) based method through leveraging the selectivity of aptamers towards cyanotoxins. A tiered approach was used to identify aptamers that have high sensitivity and specificity. First, a gold nano particle-mediated colorimetric assay was performed to confirm binding events between the aptamers of interest and the target cyanotoxin, identify the optimal concentration of aptamer, and to create a titration of the target molecule. Once aptamers had been screened via colorimetric assay, those demonstrating significant binding activity were anchored onto a gold-coated QCM sensor. The aptamer-functionalized QCM sensor was used to detect a cyanotoxin-based dose dependent signal which related to selective binding of the desired cyanotoxins.  Furthermore, non-specific targets and field samples were also examined through the QCM system to further evaluate the selective binding of aptamers towards cyanotoxins in the presence of interferences. Finally, the data, obtained through a bench-top QCM instrument, were repeated and validated on a field deployable QCM unit.

Aptamers towards rapid detection of freshwater cyanotoxins

ACS Spring 2022

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