Construction of a microfluidic optical algal biosensor in a portative system for the on-line monitoring of urban wet-weather discharges
Résumé
Urban wet weather discharges (UWWDs) can lead to a rejection of an important number of micropollutants in aquatics ecosystems, as pesticides, heavy metals or polycyclic aromatics hydrocarbons. Many pollutants detected in UWWDs have been demonstrated to impact aquatic organisms, as microalgae. Among them, herbicides as Diuron, Atrazine, etc., can impact very quickly microalgae photosynthetic metabolism. A good correlation between photosynthetic disturbance and presence of herbicides in these complex discharges has already been shown in the literature.In situ and on-line biosensors with rapid responses are consequently valuables tools to prevent the degradation of the aquatic environments quality. We propose here a new one-shot optical biosensor based on an algal immobilization into a xurography–based microfluidic chip device (Fig. 1) and chlorophyll a fluorescence measurement (biomarker of photosynthetic activity disturbance) for the toxicity detection of herbicides in UWWDs. This system has the advantages to be cheap, with a short manufacturing cycle, a very good control of sample volume, and simple whole-cell immobilization. Laboratory developments, with an optical fiber, on three algal species (Chlorella vulgaris, Pseudokirchneriella subcapitata and Chlamydomonas reinhardtii) permitted to optimize the biosensor and obtain detections limits under 0.1 ug/L of herbicides as Diuron. A portative station (fluorimeter) has been manufactured (Fig. 2) for field’s experiments and good performance have been observed for several pesticides and suggests the promising use of this tool for private industries and public urban managers of UWWDs.