Harnessing the Power of Plasmonics for in Vitro and in Vivo Biosensing

Plasmonic nanostructures exhibit localized surface plasmon resonances due to collective oscillation of conducting electrons that can be tuned by modulating the nanostructure size, shape, material composition, and local dielectric environment. The strong field confinement and enhancement provided by plasmonic nanostructures have been exploited over the years to enhance the sensitivity for analyte detection down to the single-molecule level, rendering these devices as potentially outstanding biosensors. Here, we summarize methods to detect biological analytes in vitro and in living cells, with a focus on plasmon-enhanced fluorescence, Raman scattering, infrared absorption, circular dichroism, and refractive index sensing. Given the tremendous advances in the field, we concentrate on a few recent examples toward biosensing under highly challenging detection conditions, including clinically relevant biomarkers in body fluids and nascent applications in living cells and in vivo. These emerging platforms serve as inspiration for exploring future directions of nanoplasmonics that can be further harnessed to advance real-world biosensing applications.