Resumen de Development and application of colorimetric assays and electrochemical biosensors in seafood safety
In recent years, the increased consumption of seafood products has put great pressure on efficient monitoring and management programs to protect consumer’s health and avoid economic losses to the shellfish industry. This thesis aims to contribute to both 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. Since the immobilisation of the biorecognition molecule or antigen on the support plays a crucial role in the development of biochemical devices, different immobilisation strategies are explored. Thus, self-assembled monolayers (SAMs) are used as building blocks in the development of colorimetric immunoassays for the detection of okadaic acid-group toxins and tetrodotoxins. The SAM-based immunoassays for the detection of okadaic acid are applied to the analysis of seawater samples for monitoring purposes, while the immunoassays for the detection of tetrodotoxins are used in the analysis of shellfish and human urine samples derived from a puffer fish poisoning incident. Colorimetric and electrochemical immunoassays as well as immunosensors for the detection of azaspiracids are achieved by the immobilisation of the antibody by means of 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 the detection of biogenic amines. In this case, magnetic beads are used as enzyme immobilisation supports 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. With respect to this, 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. The analytical devices developed in this thesis as well as the experimental steps presented throughout the different works (study of matrix effects, establishment of cross-reactivity factors, optimisation of the electrochemical detection, comparison between different analytical techniques, etc.) and the different examples provided regarding the application of the colorimetric assays and electrochemical biosensors, should facilitate the implementation of these powerful analytical approaches to routine seafood monitoring programs as well as to the agri-food, medical or environmental sectors in general.
