A fast and sensitive continuous flow nanobiodetector based on polyaniline nanofibrils

Polyaniline nanofibrils, fabricated as a freestanding nanonetwork in a micro gap between two gold electrodes, have been applied in a fast and sensitive analytical device for detecting microorganism cells in a flowing liquid, including the “on-line” regime. The electrical response of the device (in this case an increase in the electrical conductivity of the nanonetwork) depends on the number of cells in the sample analyzed: it is linear within the range of 0–5000 and 0–15 × 10⁶ cells injected for yeast and bacteria examined, respectively. The detection limit depends on the type of microorganism: it is about 300 and 1.9 × 10⁵ (per mL) for yeast (Saccharomyces cerevisiae) and bacteria cells (Lactobacillus rhamnosus), respectively. The results are registered within few seconds (typically 5–15 s). The device is designed to detect a low level of bio-contamination and it is expected to be useful in biomedical applications, environmental protection and anti bioterrorism systems, including “on-line” monitoring.