Fiber optic SPR sensor for human Immunoglobulin G measurement based on the MMF-NCF-MMF structure

A sensitive, simple fiber optic surface plasmon resonance (SPR) sensor based on the MMF-NCF-MMF structure is proposed in this work. The structure of the sensing part is constructed by a section of noncore fiber (NCF) sandwiched between two multimode fibers (MMF). Gold film with a thickness of 50 nm was uniformly sputtered on the outside surface of the NCF. SPR phenomenon was stimulated and experimentally verified when light propagates at the interface between the dielectric and the gold layers. The length of the NCF section was optimized by experiments and determined to be 12 mm. The refractive index (RI) sensitivity of the SPR sensor is 3475.1 nm/RIU in the RI range of 1.343-1.373. For the realization of human Immunoglobulin G detection, the surface of this SPR sensor needs to be biomodified. A simple process of polyelectrolyte self-assembled multilayers (PSAMs) deposition cycled four times utilizing diallyldimethyl ammonium chloride (PDDA) and styrenesulfonate sodium salt (PSS). And we choose goat anti-human immunoglobulin G-human immunoglobulin G as a bio-conjugated pair to examine the bio-sensing effectiveness of this SPR sensor, the maximum sensitivity of Immunoglobulin G (IgG) detection and the limit of detection (LOD) is calculated to be 57.06 nm/(mg/ml) and 1.75 mu g/ml, respectively. The proposed sensor is simple, easy to fabricate, low loss, cost-effective and can be used in numerous chemical and biological analyses.