Label-free bacteria detection using evanescent mode of a suspended core terahertz fiber

摘要

We propose for the first time an E. coli bacteria sensor based on theevanescent field of the fundamental mode of a suspended-core terahertz fiber.The sensor is capable of E. coli detection at concentrations in the range of104-109 cfu/ml. The polyethylene fiber features a 150 {\mu}m core suspended bythree deeply sub-wavelength bridges in the center of a 5.1 mm-diameter claddingtube. The fiber core is biofunctionalized with T4 bacteriophages which bind andeventually destroy (lyse) their bacterial target. Using environmental SEM wedemonstrate that E. coli is first captured by the phages on the fiber surface.After 25 minutes, most of the bacteria is infected by phages and then destroyedwith ~1{\mu}m-size fragments remaining bound to the fiber surface. Thebacteria-binding and subsequent lysis unambiguously correlate with a strongincrease of the fiber absorption. This signal allows the detection andquantification of bacteria concentration. Presented bacteria detection methodis label-free and it does not rely on the presence of any bacterial"fingerprint" features in the THz spectrum.