Sandra Leonardo Benet


This thesis aims to contribute to the development and applicability of colorimetric assays and electrochemical biosensors for the detection of marine toxins and biogenic amines, paving the way towards the implementation of low-cost, simple and reliable devices for seafood safety purposes. Colorimetric immunoassays for the detection of okadaic acid-group toxins and tetrodotoxins are developed using self-assembled monolayers as building blocks. The immunoassays for the detection of okadaic acid are applied to the analysis of seawater samples for monitoring purposes, while the immunoassays for tetrodotoxins are used in the analysis of shellfish samples and human urine samples derived from a puffer fish poisoning incident. Colorimetric and electrochemical immunoassays and immunosensors for the detection of azaspiracids are achieved by the immobilisation of the antibody through bioaffinity interactions on electrodes or using magnetic beads as immobilisation supports. Their use as powerful screening tools to monitor the presence of these toxins in mussels is demonstrated. Magnetic beads are also exploited as immobilisation supports in the development of electrochemical biosensors for biogenic amines. In this case, the beads are used for the immobilisation of enzymes and the enzyme biosensors are applied to the determination of biogenic amines in naturally spoiled fish. Furthermore, the use of diatoms as natural nanostructured supports in the development of biosensors is also explored, where biofunctionalised diatoms are immobilised on electrodes in an addressed way by means of gold electrodeposition, providing low-cost and eco-sustainable platforms and arrays with potential application in biosensing devices. Colorimetric assays and electrochemical biosensors provide powerful analytical tools that can be easily implemented in almost all the stages of food safety as well as in many other areas.