A whole cell optical bioassay for the detection of chemical warfare mustard agent simulants

Chemical warfare agents (CWAs) have become a crucial concern of the 20th century in the safety vision of the society and the environment, triggering a growing awareness for early alarm in case of terroristic attacks as well as preventing contamination. Herein, we present the development of a whole-cell optical bioassay for the detection of CWA simulants. In particular, the effects of the mustard agent simulants bis-2-chloroethyl amine and 2-chloroethyl ethyl sulphide on the unicellular green photosynthetic algae Chlamydomonas reinhardtii was studied, with the aim to unravel the response of the microorganism to the presence of these simulants and optimise the analytical conditions of the bioassay. Important variations in the growth, photosynthetic activity, and content of photosynthetic pigments were observed in the presence of the selected simulants. The algal response towards bis-2-chloroethyl amine and 2-chloroethyl ethyl sulphide in a concentration range between 0.2 and 2.5 mM was analysed, indicating a linear relationship in the measured dose-response curves and detection limits of 50 and 200 μM, respectively. Interference studies demonstrated the suitability of the proposed optical bioassay to detect mustard agent simulants also in drinking water, a defenceless matrix in case of terroristic attack, where atrazine, copper, and arsenic could be present at safety limits. Very slight matrix effect was evidenced, with ratios of 1.04 and 0.86 for calibration curves of bis-2-chloroethyl amine and 2-chloroethyl ethyl sulfide in tap water samples with respect to curves of standard solutions. Recovery values of 104 ± 15% and 97.5 ± 6.5% for 1 mM and 2 mM of bis-2-chloroethyl amine and 93 ± 16% and 105 ± 5% for 1 mM and 2 mM of 2-chloroethyl ethyl sulfide were achieved.