Multimicrobial sensor using microstructured three-dimensional electrodes based on silicon technology.

Two microbial strains with different substrate spectra were immobilized separately within a single biosensor chip featuring four individually addressable platinum electrodes. These were sputtered onto the inner surface of four isolated pyramidal cavities ("containments") micromachined on a silicon wafer. The biosensor chip was integrated into a flow-through system to measure the oxygen consumption of the immobilized microorganisms in the presence of assimilable analytes. As a model system, a yeast for the determination of biochemical oxygen demand (BOD) and a strain capable of degrading polycyclic aromatic hydrocarbons (PAH) were chosen. It was shown that the simple and mass-producible containment sensor exhibits good performance data: lower detection limit 0.1 mg/L naphthalene and 1 mg/L sensor-BOD; calibration range up to 30 mg/L; precision 3-6%; response time 2-3 min; service life up to 40 days; shelf life at 4 degrees C 6 months. The versatility of the multimicrobial sensor was demonstrated by measuring ordinary municipal wastewater samples as well as various aqueous samples contaminated with PAH. The concept of a multimicrobial sensor not only enlarges the substrate spectrum for sum parameters such as BOD but leads to additional information which allows for a more differentiated and immediate knowledge of sample composition. Using chemometrical data analysis, the multimicrobial sensor lays a foundation for developing an "electronic tongue".