Use of biosensors for the detection of marine toxins

Abstract

Increasing occurrences of harmful algal blooms (HABs) in the ocean are a major concern for countries around the globe, and with strong links between HABs and climate change and eutrophication, the occurrences are only set to increase. Of particular concern with regard to HABs is the presence of toxin-producing algae. Six major marine biotoxin groups are associated with HABs. Ingestion of such toxins via contaminated shellfish, fish, or other potential vectors, can lead to intoxication syndromes with moderate to severe symptoms, including death in extreme cases. There are also major economic implications associated with the diverse effects of marine biotoxins and HABs. Thus, effective monitoring programmes are required to manage and mitigate their detrimental global effect. However, currently legislated detection methods are labour-intensive, expensive and relatively slow. The growing field of biosensor diagnostic devices is an exciting area that has the potential to produce robust, easy-to-use, cost-effective, rapid and accurate detection methods for marine biotoxins and HABs. This review discusses recently developed biosensor assays that target marine biotoxins and their microbial producers, both in harvested fish/shellfish samples and in the open ocean. The effective deployment of such biosensor platforms could address the pressing need for improved monitoring of HABs and marine biotoxins, and could help to reduce their global economic impact.

Keywords: biosensors; harmful algal blooms; marine biotoxins; marine monitoring; shellfish poisoning.

Figure 1.. Illustration of protein phosphatase 2A (PP2A) inhibition assay concept

PP2A catalyses the conversion of p-nitrophenyl phosphate (p-NPP) into p-nitrophenol (p-NP). The coloured product can be measured spectrophotometrically. DSP group toxins, such as OA, block the binding site of the PP2A enzyme, preventing the catalysis of p-NPP.

Figure 2.. Illustration of a competitive ELISA format

Enzyme-labelled anti-toxin antibodies are added to a microwell plate coated with toxins conjugated to a carrier protein. (A) In the absence of free toxin in solution, the antibodies are uninhibited and bind to the coated surface at a high concentration. Addition of a substrate (e.g. 3,3′,5,5′-tetramethylbenzidine (TMB) in the case of horseradish peroxidase (HRP)-labelled antibodies) produces a coloured product of high intensity. (B) In the presence of free toxin in solution, the free toxin competes with the immobilized toxin-conjugate for binding to the antibodies. The uninhibited antibodies bind to the coated surface but in smaller amounts. Addition of a substrate produces a coloured product of lower intensity.