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Capillary Immunosensing System for Rapid Detection of Salmonella Typhimurium

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Paper number  037061,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.14182) @2003
Authors:   Xiao-Li Su, Zhenyu Zhang, Byungchul Kim, Yanbin Li
Keywords:   Salmonella Typhimirium, Salmonella, foodborne pathogen, immunosensor, biosensor

A capillary immunosensing system was developed for rapid detection of Salmonella Typhimirium, a common cause of bloody diarrhea and other life-threatening diseases. The system consisted of a capillary immuno-column for bacterial capture and enzymatic amplification, and an optical or electrochemical transducer for signal detection. Antibodies specific to the target bacteria were chemically immobilized onto the inner wall of fused-silica capillary column. The immobilized antibodies captured the target bacteria in a sample that was pumped through the column. Sandwich complexes of antibodies-bacteria-enzyme labeled antibodies were formed in the capillary column after enzyme-labeled antibodies passed through the column. In electrochemical detection mode, phenyl phosphate was used as the substrate of the alkaline phosphatase conjugates, and the enzymatic product phenol was detected amperometrically at a potential of 0.2 V (vs. Ag/AgCl) using a tyrosinase-horseradish peroxidase modified electrode with a flow-injection system. In optical detection, 4-nitrophenyl phosphate was used as the substrate, and optical absorbance of the product 4-nitrophenol was measured at 400 nm. The detection limit was 8.6 x 102 CFU/ml for electrochemcial mode and 8.6 x 104 CFU/ml for optical method without any preconcentration. The total assay time, from preparing the sample to obtaining the final result, was 1.5 h. The specificity of the proposed system was checked with other pathogens such as Listeria monocytogenes, S. Heidleberg, and E. coli O157:H7, and they did not interfere with the detection of S. Typhimurium.

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