Evanescent Wave DNA-Aptamer Biosensor based on Long Period Gratings for the Specific Recognition of E. coli

An evanescent wave fiber optic sensor for detection of E. coli outer membranes proteins (EcOMPs) is presented. The sensing probe is achieved by the functionalization of a Long Period Grating (LPG) inscribed in a single mode fiber (SMF28) with poly-L-lysine (PLL) resulting in a label-free configuration capable of specific recognition of EcOMPs in waters due to the resonance wavelength shift variation owing to refractive index changes of the medium (approximate to 100 nm/RIU). The sensing head was characterized and tested against EcOMP and applied to spiked environmental water samples. The sensor displayed linear responses in the range of 1x10(-10) M to 1x10(-8) M EcOMP and is regenerated (under low pH conditions) and the deviation of the subsequent detection was less than 0.1 %.