Nanoscale flagellar-motor based MEMS biosensor for explosive detection

Detection of explosive compounds has taken on a new degree of importance since 9/11 due to heightened terrorist threats. The primary goal of the current study was to design, fabricate, and test a flagellar-motor based biosensor that will provide sensitive, fast, and portable trace level detection of nitroaromatic and organic nitrate explosives, including trinitrotoluene (TNT), one of the most used explosive materials. The flagellar-motor based sensing system (FMS) integrates Escherichia coli flagellar motors with a microfluidic system to detect the presence of explosives by monitoring the rotational behavior of the flagellar filaments. The operational principle of the FMS is based on sensing the chemo-tactic responses of the nanoscale flagellar filament in the presence of nitrate or nitrite, which are the key components of explosive compounds. Our results indicated that the FMS is as sensitive as existing sensors for explosives, including the conventional electrochemical and the more portable biological based. The threshold concentrations for detection were around 50 pg of nitrate and 250 pg of nitrite on the basis of the dimension of the MEMS-based reaction system used for this study (200 mum times 50 mum times 50 mum). Using a smaller channel size can lower these low detection limits even further. Additionally, the response time of the flagellar motor biosensor is almost instantaneous due to the fast chemo-tactic response of flagellar motors to external stimuli.