## 4 Conclusions  
The development of detoxification methods for live bivalve molluscs has been attempted for a long time by several research groups. As far as we know, a truly effective and feasible methodology in a short period of time (e.g., 48 h) has not yet been found. Many of the studies carried out so far are restricted to aqueous solutions, without in vivo implementation, often leading to a false expectation of success. Based on the molecular properties of this group of toxins and considering the mode of adsorption through exchange of ions between chemical entities, we decided to explore the use of a cation-exchange resin (H-form and Na\({}^{+}\)-form) with the purpose of accelerating the detoxification process of shellfish. First, in vitro experiments were carried out using a culture of _G. catenatum_ (one of the main dinoflagellate producers of paralyzing toxins). Then, the methodology was tested in vivo using mussels (_M. edulis_), which are known as sentinel organisms and are often used in this type of studies. In vitro studies using cultures of _G. catenatum_ revealed around 80% decrease in overall toxicity upon exposure to the resin, after 48 h. Interestingly, the effect of molecular structure on the preferential adsorption of some toxins over others was evident. In this work, four main toxins (C1&2, dcSTX, GTX5, GTX6) were quantified, with dcSTX being responsible for the main decrease in toxicity, followed by GTX5. Differences were mainly attributed to steric hindrance, electronic effects, and magnitude of the overall positive charge. Although we have not identified here other analogues with high toxic potential (e.g., STX and NEO), considering the physicochemical properties of the molecules and the results obtained in this work and by other authors [38], it is expected that the adsorption of these toxins may occur successfully in solution using these cation-exchange resins. The in vivo experiments did not show evidence of a significant acceleration of the clearance process, compared to resin-free clearance. This could be due to competition from other natural substances (e.g., salts, organic matter) for the same binding sites, interactions between molecules, increasing steric hindrance and/or blocking pores, or difficulties in resin absorption by the mussel. This methodology could be promising in detoxification, but it is not yet ready to be applied. Therefore, further adjustments to the proposed methodology, such as changing the functional groups to tailor the system's physicochemical properties, are needed in follow-up work. Nevertheless, we believe that our unprecedented approach and the findings here disclosed are relevant, in that they draw attention to the importance of testing methodologies in vivo and they reveal some conditions that may strongly affect the experimental results, namely the pH-effect and its potential consequence on the metabolism and well-being of mussels. Additionally, in vivo experiments have demonstrated the occurrence of bioconversions between toxin molecules. Based on the information obtained, the production of dcSTX from GC3 (by hydrolysis) is proposed, as well as the conversion of C1&2 into GTX5.