Novel U-bent fiber optic probe for localized surface plasmon resonance based biosensor

The aim of this study is to develop an optical absorbance based biosensor suitable for wide scale use in resource-poor locales. A sensor for sensitive measurement of refractive index (RI) with the help of optical absorbance properties of gold nanoparticles (GNP) coupled to an efficient optical transducer in the form of a U-bent fiber optic probe is described. A U-bent probe was fabricated by a simple procedure. The absorbance due to the localized surface plasmon resonance (LSPR) of fiber-bound GNP was found to be linear to refractive index changes between 1.33 and 1.35. A U-bent probe of 200 μm diameter with a bend radius of 0.75 mm gave rise to a sensitivity of 35 ΔA/RIU at 540 nm. The resolution of the sensor probe was 3.8 × 10−5 RIU. Label-free biosensing was demonstrated using these probes with the help of IgG–anti IgG as bioreceptor–analyte pair.