An ISFET-algal (Chlamydomonas) hybrid provides a system for eco- toxicological tests

A cellular sensoring system was designed in which metabolism-dedicated pH-ISFETs and the unicellular green alga Chlamydomonas reinhardtii as a biological component, were combined. The system permits on-line detection of pH changes caused by the metabolic and photosynthetic activities of the cells. Photosynthetic activity results in a basification of the medium caused by uptake of CO₂. In darkness, an acidification of the medium, resulting from the production of CO₂ by degradation of starch was observed. Both, acidification and basification, are sensitive indicators for the physiological activity of the alga. Experiments using inhibitors of energy metabolism or photosynthesis illustrate the utility of this system for an on- line monitoring of substances of eco-toxicological importance.