Fig. 1. Schematic representation of the functionalization procedure to obtain E. coli responsive LC sensors, highlighting the immobilization of anti-E. coli AB on the glass surface.

Fig. 2. Schematic representation of LC-based biosensors’ detection mechanism and assembly.

Fig. 3. Photographs of the developed prototype (a) covered and (b) uncovered, highlighting the display in case of a (c) negative or (d) positive result for E. coli detection.

Fig. 4. Optical appearance of the LC-based sensors under a POM, after incubation for 30 s in E. coli concentrations. The scale bar corresponds to 100 μm.

Fig. 5. (a) Average spectra. (b) Variation of the obtained integrated spectral light flux of the ten sensor samples, after incubation for 30 s in E. coli concentrations. Values correspond to the average of three independent assays.

Fig. 6. (a) Average optical spectra obtained during the selectivity tests for four different bacteria strains and (b) corresponding POM images. The scale bar in the POM images corresponds to 100 μm.

Fig. 7. Histogram comparison of the integrated spectral light flux for the four tested sensors that were exposed to suspensions containing different bacteria (Vibrio atlanticus, Pseudomonas gallaeciensis, Acinetobacter sp., and E. coli).

Fig. 8. SEM images of E. coli attached to the activated glass slides of the sensor. The orange lines on the left image represent how the length and diameter of each bacterium were estimated using ImageJ. The obtained bacteria’s mean length was 1.59 μm, and the mean diameter was 0.47 μm.

Fig. 9. Results of the depuration tests with the LC sensors: POM images corresponding to the sample taken at (a) 0 h, (b) 0.5 h, (c) 3 h, (d) 4.5 h, (e) 22.5 h, and (f) 24 h. (g) Optical spectra obtained by analyzing the different sensors and (h) corresponding integrated spectral light flux values versus depuration time.

Fig. 10. Comparison between results obtained by analyzing different LC sensors using the integrated spectral light flux method and the percentage values obtained with the prototype.