Handheld biosensor based on nano-assembly for rapid detection of biodefense and infectious pathogens

E.C. Alocilja, Y. Wang
Michigan State University, US

Keywords: nano-assembly, nanoparticles, biosensor

Summary:

Escherichia coli (E. coli) O157:H7 is a Biodefense Category B priority pathogen and a cause of recent foodborne illness outbreaks. To effectively protect the public from this pathogen, we have developed a novel field-operable highly sensitive biosensor based on nano-assembly for the rapid detection of E. coli O157:H7. Magnetic (iron oxide), gold, and lead sulphide nanoparticles are conjugated with monoclonal and polyclonal antibodies to form MNP-Ab-Ecoli-Ab-Au-DNA-PbS assemblage in the presence of the target bacteria. The assemblage is separated from the matrix with a magnet and reported through the PbS electrochemical signal. Time to result, from sample preparation to detection, is less than one hour. Preliminary results show that the nano-assembled biosensor could detect E. coli O157:H7 cells as low as 6-10 colony forming units per milliliter (cfu/ml) with a dynamic detection range of 10^1 - 10^6 cfu/ml. Signal-to-noise ratio ranges from 1.8 to 3.7, showing robustness of the system. Furthermore, the biosensor is simple to operate, robust, and inexpensive (<$2/test). Based on these results, the biosensor has great potential for detecting low levels of biodefense agents and would be an excellent tool in defense, food safety, water quality, and public health monitoring programs.