Highly sensitive and selective localized surface plasmon resonance biosensor for detecting glutamate realized on optical fiber substrate using gold nanoparticles

In this study, we fabricated and characterized a localized surface plasmon resonance-based biosensor comprising gold nanoparticles (AuNPs) on an optical fiber substrate to detect glutamate at concentrations ranging from 0 to 10 mM. To fabricate the probe, AuNPs were decorated on an unclad portion of an optical fiber, and the enzyme glutamate dehydrogenase and coenzyme nicotinamide adenine dinucleotide were co-immobilized over the AuNPs. The sensor was designed to operate according to an intensity modulation scheme where the absorbance changed as the glutamate concentration varied in the sample around the probe. The change in the absorbance was due to the chemical reaction between glutamate dehydrogenase, glutamate, water and NAD⁺ which affected the refractive index of the medium around the AuNPs. The changes in the local refractive index led to significant variations in the absorbance of the AuNPs present in the sensing layer. The change recorded in the absorbance by AuNPs was 0.019 for the glutamate concentration range from 0 to 10 mM. The limit of detection and sensitivity of the sensor were determined as 0.36 mM and 0.0048 AU/mM, respectively. The sensor has advantages in terms of its low cost, immunity to electromagnetic interference, miniaturized probe, and capability of online monitoring and remote sensing because an optical fiber is used as the substrate for probe fabrication.