SmoColi is a bacterio-quantifier of acetaldehyde concentration that can be used as a passive smoke detector. Acetaldehyde is a toxic and carcinogenic component of cigarette smoke. It has a boiling point of 20.2 °C and is very volatile, thus can be used as an information carrier through air. The SmoColi cells are immobilized in an agarose-filled microfluidic device. The test solution is fed to one end of a microfluidic channel, in which an acetaldehyde gradient is established by diffusion and synthetic cellular degradation. The cells are engineered to sense acetaldehyde by a synthetically re-designed fungal acetaldehyde-responsive transactivator. The sensor is linked to a band-pass filter that drives GFP expression. This allows establishment of an input-concentration-dependent, moving fluorescent band displaying quantitative information about acetaldehyde. Finally, if the acetaldehyde concentration exceeds the threshold of malignance, a quorum-sensing-based mCherry alarm system springs into action, turning the entire device red.
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