In this work, a novel fiber-optic immunoglobulin G biosensor based on lossy mode resonances is proposed. This physical phenomenon is obtained by depositing a PAH/PSS layer-by-layer thin-film on a cladding removed optical fiber. A reflective configuration is used to track the generation and response of the electromagnetic resonance in the different phases of the process. According to the results, wavelength displacements of 10 nm are visualized when detecting immunoglobulins with a response time of 12 min for a 50 μg/ml concentration.
Thin-film deposition and LMR generation
The layer-by-layer electrostatic self assembly (LbL-ESA) technique  was used to adsorb the polymeric thin-film onto the monitoring fibers (Fig. 1) at room conditions (T = 23 °C and R.H. = 35%). Prior to the deposition, fibers were fixed to a dip coater (Nadetech Innovations’ ND-R) and immersed in potassium hydroxide 1 M solution during 10 min in order to acquire negative charge. After that, they were rinsed with ultrapure water to remove undesired impurities.
Keywords: Polymeric thin-films; Lossy mode resonances; Optical fiber sensors; Biosensors