A MoS2 nanoflower and gold nanoparticle-modified surface plasmon resonance biosensor for a sensitivity-improved immunoassay

Abstract

Biosensors based on surface plasmon resonance (SPR) have shown significant applications in drug screening, environmental monitoring, immunoassay, etc.; however, improving the sensitivity of these biosensors is one of the prime tasks at present. In this study, taking advantage of the special optical and morphological characteristics of MoS₂ nanoflowers, we synthesized a sensitivity-improved SPR biosensor by successively depositing MoS₂ nanoflowers and gold nanoparticles (AuNPs) on a traditional SPR sensor and then applied this biosensor to the immunoassay of mouse IgG. It was found that the deposition of the MoS₂ nanoflowers could improve the bulk refractive index sensitivity from 2212.2 to 2857.2 nm per RIU (RIU: refractive index unit); however, the further addition of AuNPs resulted in a decrease in the bulk refractive index sensitivity to 2149.7 nm per RIU. Moreover, when the proposed biosensor was applied to the IgG immunoassay, a 0.047 nm (μg mL⁻¹)⁻¹ sensitivity of the MoS₂–AuNP-modified sensor was achieved, which was ∼3 times that of the unmodified sensor (0.016 nm (μg mL⁻¹)⁻¹). This improvement in the sensitivity of the biosensor towards IgG can be attributed to the flower-like morphology of MoS₂ that provides more sites for the loading of AuNPs, thus facilitating the immobilization of a larger amount of IgG antibody on the surface of the sensor. Because of its simple fabrication process and compatibility with the standard bio-activation method of gold surface, the proposed biosensor provides an easily-accessible platform for biological analysis and detection with improved sensitivity.