Direct Functionalization of TiO2/PSS Sensing Layer for an LMR-Based Optical Fiber Reusable Biosensor

Abstract

Functionalization plays a crucial role in the development of biosensors. In this study, bioreceptors were directly immobilized onto the surface of a sensing layer after physical activation, avoiding the need for longer and more complex functionalization systems. This direct immobilization was applied to an optical sensing platform based on lossy mode resonances (LMRs) generated by a thin film of titanium (IV) dioxide/poly(sodium 4-styrenesulfonate) (TiO2/PSS). To generate the LMR, a 200-bare optical fiber was coated with TiO2/PSS using the layer-by-layer self-Assembly technique. The PSS of the sensing layer was then physically activated using either UV-ozone or plasma to immobilize antirabbit immunoglobulin G (IgG) bioreceptors. This enabled specific and label-free detection of rabbit IgG concentrations ranging from 0.002 to 2 mg/mL. The results presented in this work include the real-Time detection of rabbit IgG, a comparison between the two activation techniques (UV-ozone and plasma), and an analysis of the biosensor's reusability over four consecutive cycles, which demonstrates the promising potential of the TiO2/PSS sensing layer for biosensing applications.