Label-free fiber optic biosensor based on evanescent wave absorbance at 280 nm

Several analytes of interest such as bacteria, virus and some of the clinically important proteins and marker molecules absorb light in the ultra violet region (UV). In this study, we have investigated the possibility to develop a label-free fiber optic biosensor based on evanescent wave absorbance (EWA) at 280 nm to detect the presence of such analytes. A light emitting diode (LED) in UV with peak emission at 280 nm and span of ±10 nm was chosen as a light source to limit the solarization of the fiber probes. Numerical simulations were performed to investigate the effect of fiber parameters and wavelength of operation on EWA and its sensitivity. Experimental verifications proved the validity of the simulations. The absorbance behavior of fiber sensor probes in the visible region was studied using FITC as absorbing molecule. Goat anti-human IgG (GaHIgG) was chosen as a model analyte. Human IgG immobilized fiber probes were subjected to goat anti-human IgG to test the absorbance response of the probes at 280 nm. These studies demonstrate that intrinsic absorbance properties of biomolecules may be utilized for development of absorbance based label-free biosensors. The sensitivity, which is a limiting factor, can be improved with better optics.