Evanescent wave DNA-aptamer biosensor based on long period gratings for the specific recognition of E. coli outer membrane proteins

An evanescent wave fiber optic sensor for detection of Escherichia coli (E. coli) outer membranes proteins (EcOMPs) using long period gratings (LPGs) as a refractometric platform is presented. The sensing probes were attained by the functionalization of LPGs inscribed in single mode fiber using two different methods of immobilization; electrostatic assembly and covalent binding. The resulting label-free configuration enabled the specific recognition of EcOMPs in water by monitoring the resonance wavelength shift due to refractive index changes induced by binding events. The sensors displayed linear responses in the range of 0.1nM to 10nM EcOMPs with sensitivities of −0.1563±0.005nmdecade−1 [EcOMP, M] (electrostatic method) and −0.1597±0.004nmdecade−1 [EcOMP, M] (covalent method). The devices could be regenerated (under low pH conditions) with a deviation less than 0.1% for at least three subsequent detection events. The sensors were also applied to spiked environmental water samples. •Label-free remote evanescent wave fiber optic sensor.•The system uses regular telecommunication optical fiber in a simple and robust configuration.•Accurate quantification of E. coli proteins concentration down to 10nM in less than 1h.•Reusable sensor with a deviation less than 0.1% for subsequent detection events.•Preliminary alarm system for the detection of E. coli in environmental waters.