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