Plasmonic nanostructure biosensors based on metal are a powerful tool in the biosensing field. Surface plasmon resonance (SPR) can be classified into localized surface plasmon resonance (LSPR) and propagating surface plasmon polariton (PSPP), based on the transmission mode. Initially, the physical principles of LSPR and PSPP are elaborated. In what follows, the recent development of the biosensors related to SPR principle is summarized. For clarity, they are categorized into three groups according to the sensing principle: (i) inherent resonance-based biosensors, which are sensitive to the refractive index changes of the surroundings; (ii) plasmon nanoruler biosensors in which the distances of the nanostructure can be changed by biomolecules at the nanoscale; and (iii) surface-enhanced Raman scattering biosensors in which the nanostructure serves as an amplifier for Raman scattering signals. Moreover, the advanced application of single-molecule detection is discussed in terms of metal nanoparticle and nanopore structures. The review concludes by providing perspectives on the future development of plasmonic nanostructure biosensors.

The Au–TiO₂–AuNPs biosensor achieved the resonant coupling of plasmon-waveguide resonance to localized surface plasmons. The limit of detection for the specific detection of carcinoembryonic antigen was as low as 3 ng mL⁻¹.

We report a comprehensive sensitivity comparison of the PSPR and the resonant coupling mode between PSPR and LSPR biosensors. It could be a guide for the design of plasmonic sensors for detecting multiple substances at different scales.

A sensor based on plasmon-waveguide resonance (PWR) exhibits an impressive narrow linewidth and has attracted extensive attention in plasmon label-free sensing. However, the low surface electric field intensity limits the detection ability of biomolecules, where the refractive index changes are restricted at the sensor surface. In this study, we study the coupling of PWR and multiple plasma modes in a hyperbolic metamaterial (HMM), combining narrow linewidth and electric field enhancement advantages. The PWR-HMM sensor includes a gold film, lossless dielectric layer, and metal/dielectric multilayer HMM array composed of 2-layer Au/Al ₂ O ₃ stacks. The evanescent field of PWR is used to excite multiple plasma modes in the HMM. The figure of merit of the proposed structure reaches 5417/RIU owing to the existence of lossless dielectric layer, which is 11.7 times than the conventional gold film structure. The maximum bulk sensitivity of the PWR-HMM sensor was 43 000 nm/RIU. In comparison with PWR, the surface electric field intensity and the surface sensitivity of PWR-HMM increase by four and two times, respectively. Furthermore, comparing the sensing performance of the PWR-HMM sensor and PWR-nanoparticle (NP) sensor (coupling PWR and localized surface plasmon resonance), it was found that PWR-HMM has 20% higher surface sensitivity than the PWR-NP. A sensing mechanism coupling PWR and multiple plasma modes in the HMMs opens a gate to significantly improve the PWR sensors performance, which is expected to be used to resolve urgent issues in biological, medical and clinical applications.