Rapidly determining E. coli and P. aeruginosa by an eight channels bulk acoustic wave impedance physical biosensor

A new automatic instrument based on an eight channels bulk acoustic wave (BAW) impedance physical biosensor was developed and applied to determine E. coli and P. aeruginosa in amino acid broth. The corrosion resistances of electrode was important for the stability of BAW impedance physical biosensor, so corrosion resistances of 316 stainless steel (ss) electrodes were investigated by polarization experiments, the results showed 316 ss passivated by trioxide chromium solution were better than by others. The inflexion-point time (IT) for quantitative determination at which the frequency changed most rapidly in response curve was easy to determine and the relationships between IT and the logarithm of the initial concentration of E. coli and P. aeruginosa were linear in the range of 60 to 4 × 106 cells/mL. Furthermore, the stability, uniformity and reproducibility of the instrument were studied. To sum up, this instrument was durable, sensitive, and cheap. It gave out the potential uses for determining the concentrations of bacteria and monitoring in real time the kinematics of bacteria growth.