| Abstract
| - Piezoelectric-excited millimeter-sized cantilever (PEMC)sensors immobilized with antibody specific to Escherichiacoli (EC) O157:H7 is used to detect EC at 1 cell/mL in 1mL and 1 L samples in a batch and flow mode, respectively.Two sensor designs were used. The first design (PEMC-a) has both the piezoelectric and non-piezoelectric layeranchored, while in the second design (PEMC-b) had only thepiezoelectric layer anchored. PEMC-a, used in batchmode with 1 mL sample, showed limit of detection at 10 cells/mL using the second bending mode at 85.5 kHz in air.PEMC-b exhibited resonant frequencies at 186.5, 883.5, and1778.5 kHz in air and 162.5, 800.0, and 1725.5 kHz insample flow conditions. A one-liter sample containing1000 EC cells was introduced at 1.5, 2.5, 3, and 17 mL/min,and the change in resonant frequency was monitored.The total frequency change observed for the mode at 800kHz and sample flow rates of 1.5, 2.5, 3, and 17 mL/minwere 2230 ± 11, 3069 ± 47, 4686 ± 97, and 7188 ± 52 Hz,respectively. Each detection experiment was confirmedby exposing the sensor to a low pH solution followed bya phosphate buffered saline (PBS) rinse, which caused therelease of the attached EC. The final frequency changeobserved was nearly identical to the value prior to ECattachment. Kinetic analysis showed that the observedbinding rate constant at 1.5, 2.5, 3 mL/min were 0.009, 0.015,and 0.021 min-1, respectively. The significance of theseresults is that very low concentration of pathogens in largesample volumes can be measured in a short time periodwithout the need for filtration or enrichment.
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