Sensitivity-Enhanced Optical Fiber Biosensor Based on Coupling Effect Between SPR and LSPR

An optical fiber biosensor based on gold nanoparticles and protein A co-modified Au film coated photonic crystal fiber (Au-PCF) is proposed and demonstrated for human IgG detection. For the electric field coupling effect between surface plasmon resonance (SPR) of Au film and localized surface plasmon resonance (LSPR) of gold nanoparticles, the refractive index sensitivity can be enhanced significantly. Besides, goat anti-human IgG is immobilized by protein A modified on the gold nanoparticles surface to interact with human IgG. Protein A can specifically bind the Fc region of the antibodies and has a high degree of orientation for capturing antibodies. Experimental results indicate that the refractive index sensitivity of Au-PCF sensor modified gold nanoparticles reaches 3915 nm/RIU, which is about 1.6 times higher than the Au-PCF sensor without gold nanoparticles modified. The lowest detection limit of human IgG based on gold nanoparticles and protein A co-modified Au-PCF sensor is 37 ng/mL, which is about 2.4 times and 6.3 times lower than gold nanoparticles-Au-PCF sensor and Au-PCF sensor, respectively. Such a sensitivity enhanced optical fiber biosensor based on SPR-LSPR coupling effect has potential application in clinical disease diagnosis and immunoassays.