Cyanobacteria exist around the world and they are found in mass occurrences partly due to climate change. Some cyanobacterial strains produce toxins and the moststudied and abundant toxic groups are cyclic structured microcystins and nodularin that are hepatotoxic. Toxins should not be found in domestic water and therefore microcystins are controlled by the authorities. The most severe variant of cyanobacterial toxins is microcystin LR (MC-LR) and World Health Organization has set a guidance limit for MCLR concentration in drinking water, 1 µg/L.

There are already several analytical methods available to detect microcystins and nodularin from drinking water, for example competitive and non-competitive immunoassays, high performance liquid chromatography (HPLC) and mass spectrometry. However, there are some problems in the current methods. Methods are not sensitive enough, methods are slow or methods need expensive and large equipment. A rapid, easy to use and cost-effective method would improve the detection of the quality of the drinking water.

The aim of this Master’s thesis was to develop two bioluminescence based noncompetitive immunoassays to detect microcystins and nodularin. The first assay is a traditional non-competitive immunoassay and the other assay is based on complementation of the enzyme. In this study, two antibody constructs were designed: i) a primary antibody anti-ADDA Fab that recognizes the cyclic structured microcystin and nodularin and ii) a secondary antibody that recognizes the immunocomplex which is formed by anti-ADDA Fab and microcystin or nodularin. Luciferase enzyme NanoLuc was fused to secondary antibody. When substrate furimazine catalyzes this chemical reaction, it produces light.

According to preliminary test results, activity is detected in anti-ADDA Fab and NanoLuc-Fab-fusion produced light when it recognized the immunocomplex formed by anti-ADDA Fab and microcystin. This enables further development of the immunoassay which is based on the enzyme complementation.