Terahertz immunosensing assisted by functionalized Au NPs based on all-dielectric metasurface

Terahertz (THz) sensors have attracted significant attention in the biological field due to their non-destructive and harmless interaction with biochemical samples, but how to achieve efficiently specific sensing for the small molecular weight samples is still challenging. In this work, we incorporated an all-dielectric metasurface with the functionalized gold nanoparticles (Au NPs) to realize an immunosensing of the target biomolecule at nanomole-level concentration. These Au NPs are modified by the Anti-HA tag antibody, which realizes the specific immunobinding of the human influenza hemagglutinin tag protein (HA antigen). By comparing with and without the functionalized Au NPs, the experimental results show that this sensor can quantitatively detect the concentration of HA antigen, and its sensitivity can be greatly improved by the functionalized Au NPs. The maximum sensitivity can be achieved to 2.96 GHz∙ml/nmol, which is 2.66 times higher than that without the Au NPs, and the highest detection accuracy reaches 1.05 nmol/ml. Furthermore, by comparing three other nonspecific proteins, only the HA antigen can be sensitively distinguished, which proves the specificity of this sensing method. Our results illustrate a reliable platform for THz immunosensing applications, and it is expected that the proposed sensing strategy opens new avenues for developing high-efficient, low-cost, and real-time THz all-dielectric sensors for biomolecular detection.