This paper presents an immunobiosensor of fast response time to detection of bacteria, made by Plastic Optical Fiber. Probes were tested in U-shaped and Meander-shaped to investigate the best sensitivity, accuracy and repeatability. During calibration was used for sucrose solutions refractive index (RI) from 1.33 to 1.39. This is equivalent to IR range of the water and the highest concentration of bacteria, respectively. Immunobiosensor was able to detecting the presence of enteropathogenic Escherichia coli in water from suspensions of different concentrations of 10<sup>6</sup> and 10<sup>4 </sup>colonies forming units per millilitre (CFU/mL) in twenty minutes.
This work presents a novel, fast response time, plastic optic fiber (POF) biosensor to detect Escherichia coli. Different forms of probes in U-shaped format were tested: U-shaped with different radii, coil-shaped and meander-shaped. In the calibration process we used solutions of sucrose for obtaining refractive indexes (RI) in the range 1.33 – 1.39 RIUequivalent of water and bacteria, respectively. The POF probes were functionalized with antibody anti<i>-Escherichia coli</i> serotype O55 and tested with bacteria concentrations of 10<sup>4</sup>, 10<sup>6</sup> and 10<sup>8</sup> colonies forming unities/mL (CFU/mL). The optoelectronic setup consists of an 880 nm LED connected to the U-shaped probe driven by a current source controlled by an Arduino Microcontroller. At the opposite fiber end, the light received by a photodetector is amplified and read by the A/D port of the microcontroller. The output voltage decreases as the external RI increases, accordingly to the bacteria that is captured by the antibody fixed in the biosensor. The paper presents results obtained with the different shapes of probes tested with the same setup and biochemical protocol. In conclusion the system shows good capabilities of having concentration measurements results in less than 10 minutes with uncertainty of 10<sup>-4</sup> RIU enabling a future capacity to read concentration of 10<sup>3</sup> CFU/mL.
This work has the objective to research and develop a plastic optical fiber biosensor based taper and mPOF LPG techniques to detect Escherichia coli by measurements of index of refraction. Generally, cell detection is crucial in microbiological analysis of clinical, food, water or environmental samples. However, methods current employed are time consuming, taking at least 72 hours in order to produce reliable responses as they depend on sample collection and cell culture in controlled conditions. The delay in obtaining the results of the analysis can result in contamination of a great number of consumers. Plastic Optical Fiber (POF) biosensors consist in a viable alternative for rapid and inexpensive scheme for cells detection. A study the sensitivity of these sensors for microbiological detection, fiber Tapers and Long Period Grating (LPG) both in poly-methyl-methacrylate (PMMA) were realized as possible candidates to take part of a biosensor system to detect Escherichia coli in water samples. In this work we adopted the immunocapture technique, which consists of quantifying bacteria in a liquid sample, attract-ing and fixing the bacteria on the surface of the polymer optical fiber, by the antigen-antibody reaction. The results were obtained by optical setup that consists in a side of the fiber a LED coupled to a photodetector through a POF with the taper in the middle of it. On the other side of the POF a photodetector receives this light producting a photocurrent. The output voltage is fed into the microcontroller A/D input port and its output data is sent via USB to a LabView software running in a microcomputer. The results showed the possibility of the POF in biosensor application capable to detect E. coli for environmental and food industry and for detecting and identifying biological-warfare agents using a very rapid response sensor, applicable to field detection prototypes.