Proceedings Detection of Alexandrium minutum dinoflagellate in environ- mental samples using electrochemical genosensor † Stephanie L. Morais 1 , Piedade Barros 2 , Marlene Santos 2 , Cristina Delerue-Matos 1 , Andreia C. Gomes 3 and M. Fátima Barroso 1, * 1 REQUIMTE/LAQV, Instituto Superior de Engenharia do Porto, Instituto Polit´ecnico, Rua Dr. Ant´ onio Bernardino de Almeida 431, 4200-072, Porto, Portugal 2 CISA|ESS, Centro de Investigaçao ˜ em Saúde e Ambiente, Escola Superior de Saúde, Instituto Polit´ecnico do Porto, Rua Dr. Ant´ onio Bernardino de Almeida, 400, 4200- 072, Porto, Portugal 3 Centro de Biologia Molecular e Ambiental (CBMA), Departamento de Biologia, Universidade do Minho, 4710-057, Braga, Portugal * Corresponding: mfb@isep.ipp.pt † Presented at the 1st International Electronic Conference on Chemical Sensors and Analytical Chemistry, 01—15 July 2021 ; Available online: https://csac2021.sciforum.net/. Abstract: Dinoflagellates are aquatic microorganisms that inhabit both salt and fresh waters. These microorganisms are mostly harmless, however, under certain conditions, some species rapidly re- produce forming water blooms that not only discolor the waters but also compromise the health of every organism in the vicinity, as some dinoflagellates produce potent toxins deemed unsafe for human health (e.g. Alexandrium minutum). In this work, a disposable electrochemical genosensor for the detection of the toxic dinoflagellate Alexandrium minutum was developed. The analytical plat- form methodology consisted in a sandwich format heterogeneous hybridization of complementary DNA sequences assay. The 70 bp A. minutum-specific targeting probe, the 45 bp fluorescein isothi- ocyanate-labelled signaling DNA probe and the 25 bp thiolated-DNA-capture probe were designed, after analyzing public databases. To maximize the complementary DNA hybridization and to avoid the formation of strong secondary structures, a mixed mercaptohexanol (MCH) and self-assembled monolayer (SAM) A. minutum-specific DNA-capture probe was immobilized onto disposable screen-printed gold electrodes (SPGE). Using chronoamperometric measurements, the enzymatic amplification of the electrochemical signal was obtained with a concentration range from 0.12 to 1.0 nM, a LD of 24.78 pM with a RSD < 5.2 %. This electrochemical genosensor was successfully applied to the selective analysis of the targeted A. minutum specific region of denatured genomic DNA, ex- tracted from toxic dinoflagellates present in the Atlantic Ocean. Keywords: Alexandrium minutum; Chronoamperometry; Electrochemical genosensor; Sandwich for- mat hybridization; Screen-printed gold electrodes. 1. Introduction Rivers, lakes, estuaries, beaches, among others, are major economic and ecological sources for humans and their daily activities (e.g. fisheries, agriculture, tourism, aquacul- ture, ...) [1]. Nevertheless, the increase of these actions has slowly compromised the fun- damental ecological structure of these aquatic ecosystems, turning them into favorable environments for phytoplankton microalgae growth and proliferation. This phenomenon is known as algae blooms [2,3]. Dinoflagellate blooms are a natural and, in most cases, beneficial event, since they increase the available resources to feed fishes and other aquatic organisms, contribute to the reduction of atmospheric carbon emissions and regulate the aquatic nutrient cycle [4]. Published: 17 August 2021 Publisher’s Note: MDPI stays neu- tral with regard to jurisdictional claims in published maps and institu- tional affiliations. Copyright: © 2021 by the authors. Submitted for possible open access publication under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/b y/4.0/).