Real-Time Salmonella Detection Using Lead Zirconate Titanate-Titanium Microcantilevers

Abstract

Current methods for analysis of unknown powders in suspicious packages involve sending samples to laboratory facilities where a variety of time-consuming tests are performed. We have developed and investigated the use of a lead zirconate titanate -titanium (PZT-Ti) microcantilever for in situ detection of the common food-and water-born pathogen, Salmonella typhimurium. Using a bifunctional linking molecule to immobilize antibody on the titanium surface of the microcantilever, we can directly detect salmonella cells in suspensions of differing concentration. This novel surface functionalization technique along with the sub-nanogram sensitivity of the cantilever has allowed for direct quantification of S. typhimurium cells in suspension.

In situ detection of Bacillus anthracis spores using fully submersible, self-exciting, self-sensing PMN-PT/Sn piezoelectric microcantilevers

“…Other researchers have demonstrated optically monitored silicon microcantilever ex situ detection of just one E. coli bacterium in vacuum, 24 and in situ detection of 10 5 Bacillus spores ml 21 . 25 In contrast to the optical monitoring requirements of these silicon-based sensors, piezoelectric cantilever sensors consisting of a piezoelectric layer such as lead zirconate titanate (PZT) bonded to a nonpiezoelectric layer such as stainless steel, 26 titanium, 27 or glass 28 have the advantage of electrical self-excitation and self-sensing for potential in situ electrical detection. With antibodies immobilized on the cantilever surface specific to target antigens, binding of such antigens to the antibodies on the sensor surface causes the cantilever's resonance frequency to shift, which is quantified electrically.…”

“…To date, reported piezoelectric cantilever biosensors were either millimetre-size cantilevers made by bonding commercial PZT to a stainless steel, titanium, or glass nonpiezoelectric layer, or were microcantilevers microfabricated from PZT [29][30][31] or zinc oxide 32 thin films deposited on a silicon wafer. Although the millimetre-size PZT cantilevers 26,27 can perform in situ detection without electrically insulating the PZT simply by dipping only the nonpiezoelectric tip, they lack the sensitivity of thin-film-based PZT microcantilevers. On the other hand, thin-film-based microcantilevers have shown better sensitivities such as in tip-dipping detections of DNA and proteins using PZT microcantilevers, 30 and in-air detection of ethanol and water vapor using zinc oxide microcantilevers.…”