Nanostructured Surfaces as Plasmonic Biosensors: A Review

Conventional laboratory techniques exhibit impressive sensing performance and still constitute an irreplaceable tool in bioanalytics. Nevertheless, high costs, time consumption, and need for well-equipped laboratories and skilled personnel make highly desirable to explore novel strategies to carry out biochemical analyses. In this regard, biosensor-based methods represent a promising approach to keep affordability and rapidity, thus they can inherently pave the way to point of care tests and high-throughput analysis. Regrettably, most of them suffer from fabrication and biofunctionalization complexity, and poor sensitivities and reliability. Therefore, their adoption as a real alternative to the gold standards is still far from being achieved. However, the massive research on plasmonic nanostructures is revealing their potentialities in sensing field, since they own appealing performances resulting from the plasmon-related effects and can be easily adapted to a large variety of applications. In this review, a summary of plasmonic biosensors recently devised is reported. Though many nanostructures fit for shared applications, for clarity they are classified into two main categories: i) biosensors whose sensing parameters are plasmon-related observables (localized, coupled, lattice surface plasmon resonances) and ii) biosensors in which the nanostructure acts as amplifier for an external signal (surface-enhanced Raman and infrared spectroscopies and plasmon-enhanced fluorescence).