A Fiber Optic Particle Plasmon Resonance Biosensing Platform Based on Detection of Light Scattering Intensity from the Proximal End

A novel light scattering sensing platform was constructed on the basis of modification of the unclad portion of an optical fiber with self-assembled gold nanoparticles. The light scattering signal from the sensor fiber can be collected from the side surface or from the proximal end. In general, collection from the proximal end is more sensitive and the sensitivity increases with increasing sensor length. When excited at 673 nm, the light scattering signal from the sensor fiber increases linearly with increasing refractive index of samples. This change in the light scattering property of a gold nanoparticle in solutions of different refractive indexes has been confirmed by simulations. Furthermore, the gold nanoparticle surface was functionalized with L-cysteine or biotin to allow selectivity of the sensor. With excitation at 442 nm, results show that the light scattering signal increases linearly with increasing concentration of each analyte. Detection limits of the sensor for Cu2+ ion and streptavidin were determined to be 0.16 ppb and 3.3 x 10(-10) M, respectively. This label-free biosensing capability has also been confirmed by simulations of the scattering cross-sections of biotin-modified gold nanoparticles at various surface coverages of streptavidin.