Portable Microalgal Biosensor for Herbicide Monitoring

The need for in-situ and real-time tools to monitor the fate of pesticides in extensive areas is of great concern to preserve the environment in countries where agroindustry represents an essential part of its economy. In this work, we present the construction of a portable system based on the reversible photosynthesis inhibition produced by herbicides on microalgae, using atrazine as a model compound. The decrease in oxygen production due to the photosynthesis inhibition is electrochemically detected using an automated flow system. The system presented here involves the immobilization of microalgae in a polyelectrolyte-surfactant-carbon nanotube self-assembled material cast on a screen-printed graphite electrode; these components contribute to the stability and sensitivity of the whole device. The system presents a limit of detection of 0.11 mu M, showing an excellent performance in river samples. The sensor maintains its integrity after five months immersed in a freshwater algae medium at room temperature. These features are key to install this system along the course of a river at a low cost, allowing early detection of polluted areas and long term environmental studies.