Recent advances in metallic nanobiosensors development: colorimetric, dynamic light scattering and fluorescence detection

Noble metal nanoparticles (NPs) such as gold and silver, in the size range of 5–100 nm possess unique plasmonic properties such as light scattering and absorption, which can be altered by changing their shape, size, chemical composition, and even the dielectric constant of the medium; while the ultrasmall metal nanoclusters (NCs) with size less than 2 nm exhibit photoluminescence and molecular-like properties due to quantum confinement effects. These nanosized metal are useful optical sensing probes for detecting a wide range of biological analytes. In this review, we first highlight the synthesis methods of metal nanostructures and their unique optical properties. It is followed by reviewing the recent advancement in metallic nanobiosensors designs and their sensing principles, which includes colorimetric, dynamic light scattering (nanoDLS) and fluorescent detection. Finally, the prospect and challenges in developing highly robust and ultrasensitive metallic nanobiosensors towards translational clinical diagnostics and advanced applications in theranostic for future nanomedicine are discussed.