Sensors that are exceptionally sensitive with real-time outputs and minimal consumption of reagents are needed to continuously monitor air and water against bioterrorist incidents. Amplifying fluorescent polymers (AFP) provide exceptionally sensitive real-time reagentless sensor platforms as applied to detection of nitroaromatic explosives. This platform technology has the potential to be adapted to detect biological warfare (BW) agents by covalently attaching the 5’ end of stem-loop molecular beacons to AFP as DNA hybridization signal transduction switches. Molecular beacons with loop sequences specific for sequence signatures of a target BW agent are configured with a quencher on the end of the 3’ arm of the stem-loop. The AFP is quenched in the absence of target DNA, but upon hybridization with target the stem is melted, the duplex loop extended, and the AFP dequenched. This signal transduction is reversible upon removal of the target sequence with the molecular beacon reforming the stem-loop conformation. Proof-of-concept research has demonstrated that molecular beacons for signature sequences of Francisella tularensis result in correct identification of the presence of this agent in samples, but no false positives were seen with Escherichia coli.
Nomadics and Professor Timothy Swager have collaborated extensively on the development of Amplifying Fluorescent Polymer (AFP) sensing technologies. AFPs are fully conjugated polymers which link many fluorphores into what is in effect, a molecular wire. Once linked, the ensemble of fluorophores will respond to a transduction event at any individual fluorophore. As a result, each individual analyte interaction will produce an effect in a much larger ensemble of fluorphores, amplifying each sensing event. Nomadics capitalized on this effect to construct a handheld landmine detector, which can identify buried landmines by sensing the trace signature of TNT vapor emanating from a mine. This presentation will describe efforts of Nomadics and the Swager group to leverage the intrinsic amplification of AFP systems for bioanalyte detection.
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