Recent trends in the detection of freshwater cyanotoxins with a critical note on their occurrence in Asia

Cyanobacteria are highly prevalent in slow-moving and nutrient-rich water bodies due to changing climatic conditions, eutrophication, and anthropogenic activities. Toxins of cyanobacterial blooms, i.e., cyanotoxins are also increasing at alarming rates in freshwater. Several efforts are being taken to detect cyanotoxins using molecular and analytical techniques to understand their occurrence and distribution, however, these studies are discrete and localized. The detection of cyanotoxins within water bodies is a long-established challenge. In this article, conventional methods of detection and the recently used nanostructure based immuno-sensors are described. Several studies are considered where aptamers are utilised as the biorecognition probe and we have discussed their use in colorimetric, electrochemical and optical sensors for the detection of cyanotoxins. Furthermore, this article also reviews the current field deployable diagnostics for the real-time monitoring of cyanotoxins. Future work on fundamental studies, development of highly specific aptamers for recognising different congeners of cyanotoxins and the integration of sensors into portable or lab-on-a-chip devices could be interesting and useful research. Moreover, several studies related to the occurrence and distribution of cyanotoxins in the freshwater bodies of Asia are reviewed, with potential threats identified. This article also adds a note on the geographical distribution and detection of cyanotoxins in Asia. Thus, we have provided an overview of various evolving detection systems that could be employed in identified problematic underdeveloped regions to improve management strategies to monitor and control cyanotoxins.