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

Abstract

In this study, we have demonstrated in situ, all-electrical detection of Bacillus anthracis (BA) spores using lead magnesium niobate-lead titanate/tin (PMN-PT/Sn) piezoelectric microcantilever sensors (PEMS) fabricated from PMN-PT freestanding films and electrically insulated with methyltrimethoxysilane (MTMS) coatings on the tin surface. Antibody specific to BA spore surface antigen was immobilized on the platinum electrode of the PMN-PT layer. In phosphate-buffered saline (PBS) solution, the PMN-PT/Sn PEMS exhibited quality (Q) values ranging from 50 to 75. The detection was carried out in a closed-loop flow cell with a liquid volume of 0.8 ml and a flow rate of 1 ml min(-1). It was shown that one sensor, "PEMS-A" (500 microm long, 800 microm wide, with a 22 microm thick PMN-PT layer, a 20 microm thick tin layer and a 1 +/- 0.5 x 10(-12) g Hz(-1) mass detection sensitivity) exhibited resonance frequency shifts of 2100 +/- 200, 1100 +/- 100 and 700 +/- 100 Hz at concentrations of 20,000, 2000, and 200 spores ml(-1) or 16,000, 1600, and 160 total spores, respectively. Additionally, "PEMS-B" (350 microm long, 800 microm wide, with an 8 microm thick PMN-PT layer, a 6 microm thick tin layer and a 2 +/- 1 x 10(-13) g Hz(-1) mass detection sensitivity) exhibited resonance frequency shifts of 2400 +/- 200, 1500 +/- 200, 500 +/- 150 and 200 +/- 100 Hz at concentrations of 20,000, 2000, 100, and 45 spores ml(-1) or 16,000, 1600, 80, and 36 total spores, respectively.

Relaxor-PT Single Crystal Piezoelectric Sensors

“…This finding indicated that PMN-PT PEMS can withstand liquid damping better and exhibit a much larger Q factor in liquid, despite of their low Q factor in air (~75). As a result, the PEMS (500 × 800 × 42 μm 3 ) exhibited the resonant frequency shift of 2100 ± 200 Hz at concentration of 20,000 spores/mL [119].…”

“…McGovern et al [119] initially reported in situ detection of Bacullus anthracis (BA) spores using the PMN-PT crystal as a sensing material. They developed PMN-PT/Sn piezoelectric micro-cantilever sensors (PEMS) which were electrically insulated with methyl-trimethoxysilane (MTMS) coatings on the tin surface.…”

Array lead zirconate titanate/glass piezoelectric microcantilevers for real-time detection of Bacillus anthracis with 10 spores/ml sensitivity and 1/1000 selectivity in bacterial mixtures

“…From our earlier studies, a typical saturation time ranges from a few minutes at higher concentrations, e.g., 10 5 spores/ ml to 15-30 min at lower concentrations, e.g., 10 1 spores/ ml. [20][21][22][23]26 The present detection scheme allowed us to detect BA over a wide range of concentrations, 10 1 -10 7 spores/ ml over a short time. While these experiments did not yield a linear dose response of the PEMS to these concentrations of BA, which would require preparing the sensor surface after detection at each concentration, they nonetheless amply demonstrated the "repeatability" of the detection from sensor to sensor, which is one of the main goals of this study.…”

“…27 Due to thickness and size differences, for micrometer-size bacteria detection, a 127-m-thick PZT/glass PEMS exhibited a concentration limit of 500-1000 bacteria/ml 20,21 while an 8-mthick PMN-PT PEMS exhibited a much lower 36 total spore sensitivity. 26 More recent studies showed that PEMS flexural-mode detection resonance frequency shift was primarily due to the elastic modulus change in the piezoelectric layer from the stress induced by the binding of the target analyte to the PEMS surface. 28,29 As a result, the detection sensitivity of a PMN-PT PEMS and that of a PZT PEMS was, respectively, 300 times 28,29 and 100 times 20,21 higher than could be accounted for by mass loading alone.…”

“…Real-time, label-free antigen detection is achieved by electrically monitoring the PEMS flexural resonance frequency shift. [19][20][21][22][23][24][25][26] PEMS flexural-mode detection sensitivity is related to the thickness and the size of the PEMS. Generally, a PEMS flexural-mode detection sensitivity increases with a reduced PEMS size and thickness.…”