|Tu, Shu I|
Submitted to: Biosensors and Bioelectronics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2006
Publication Date: 7/10/2006
Citation: Campbell, G.A., Uknalis, J., Tu, S., Mutharasan, R. 2006. Piezoelectric excited millimeter-sized cantilever (pemc) sensor detects escherichia coli 0157:h7 in two-hour incubated samples at 4 cfu per gram of beef. Biosensors and Bioelectronics. 22(2007)1296-1302 Interpretive Summary: Contamination of pathogenic bacteria, e.g., E coli O157:H7 in foods may lead to serious public health concerns. Thus, there is a need to rapidly, sensitively and specifically detect the pathogen in foods. For this purpose, a new biosensor called Piezoelectric-excited millimeter-sized cantilever (PEMC) sensor was developed. The sensor can record the small weight increase resulting from the binding of targeted bacteria. When applied to the ground beef system, the sensor was able to detect ~ 1 cell of the E. coli in 1 gram of the beef. This information is useful for the food industry and research community to develop practical detection instruments for food safety and security.
Technical Abstract: Piezoelectric-excited millimeter-sized cantilever (PEMC) sensors consisting of a piezoelectric and a borosilicate glass layer with a sensing area of 4 mm square were fabricated. Antibody specific to Escherichia coli (anti-E. coli) O157:H7 was immobilized on PEMC sensors, and exposed to six different E. coli samples: broth without inoculation of cells served as control, broth inoculated with E. coli O157:H7 at 25 cells/100 mL, 100 mL broth containing 25 grams of beef (both sterilized and unsterilized), and 100 mL broth with 25 grams of beef (both sterilized and unsterilized) and 25 E. coli O157:H7 cells. The resonant frequency decreased at a rate proportional to E. coli O157:H7 concentration and reached a steady state value. The total resonant frequency change obtained for the broth plus E. coli O157:H7 samples were 0 +/- 2 (n=2), 16 +/- 2 (n=2), 30(n=1), and 54 +/- 2 (n=2) Hz corresponding to 0 h, 2 h, 4 h, and 6 h growth at 37 C, respectively. The total resonant frequency response to the broth plus 25g ground beef plus E. coli O157:H7 cells were 0 +/- 2 (n=2), 21 +/- 2 (n=2), 37 (n=1), and 70 +/- 2 (n=2) Hz corresponding to 0 h, 2 h, 4 h, and 6 h, respectively. Exposure to low pH buffer released the attached cells causing the resonant frequency to return to the value prior to the detection experiment, confirming that the resonant frequency response was due to E. coli O157:H7 attachment. The Most Probable Number plating technique was used to determine the concentration of E. coli O157:H7 in the broth-E.coli O157:H7 samples as 0, 33, 210, and 4,400 CFU per mL, corresponding to 0 h, 2 h, 4 h, and 6 h, respectively. These results suggest that detection of E.coli O157:H7 at approximately 1 CFU/mL was accomplished using PEMC sensors.