Optical fiber biosensor based on surface plasmon resonance.

Abstract

In this report, we explore a surface plasmon resonance (SPR) fiber optics system that can be used as a convenient and cost-effective biosensor for the measuring of antibody binding activities. The phenomenon relies on the increase in refractive index when binding activities occur on the sensing interface, resulting in a red shift of the SPR wavelength. The fibers are created by splicing a length of photonic-crystal fiber (PCF) with collapsed regions in between multi-mode fibers (MMFs) and subsequently coating the PCF region with gold.

The fabricated gold-coated fibers are then evaluated by using varying concentrations of sodium chloride solutions to test for their refractive index sensitivity. A linear relation is observed between the SPR wavelength shifts and the refractive indexes from 1.330 to 1.377. This result indicates that the fibers are suitable for bio-sensing purposes.

For bio-sensing, binary mixtures of 11-mercaptoundecanoic acid (MUA) and 6- mercaptohexanol (C6OH) are adsorbed onto the gold-coated fibers via Au-S bonds to produce mixed self-assembled monolayers (SAMs). This allows for the efficient covalent binding of Protein G (PrG), which in turn has a high affinity for the immobilization of IgG. Varying concentrations of anti-IgG is quantified by binding them to the IgG and subsequently measuring the SPR wavelength shifts of the samples. The results obtained indicate that the system can be used to effectively quantify anti-IgG concentrations varying from 1mg/L to 30mg/L.