Plasmonic Optical Imaging of Biological Samples

Plasmonic nanoparticles, particularly gold and silver, are significant for various biomedical applications as they have unique plasmonic properties due to their interactions with light and functions as excellent and stable bioimaging agents. The plasmonic properties of nanoparticles have kindled researches and applications in in vitro and in vivo imaging and diagnosis as well as therapy. Hence, they have been employed in the development of imaging probes and therapeutic carriers. Optical imaging is crucial in numerous biological studies but still, there are challenges in terms of sensitivity, resolution, depth of penetration, and speed. Few techniques for plasmonic nanoparticle-based imaging are dark-field microscopy, differential interference contrast microscopy, fluorescence-based microscopy, surface-enhanced Raman scattering microscopy, interferometric scattering microscopy, and saturated excitation microscopy. Optical microscopy is a fundamental part of biophotonics and biomedical research, and hence numerous groundbreaking techniques like super-resolution optical microscopy have been developed. It has led to the techniques exploiting plasmonic nanoparticles used in quantitative and sensitive tracking of biological particles to investigate various cellular mechanisms. Progress has been made in plasmonic imaging using different shapes of nanoparticles as they are advantageous in regulating image resolution and specificity. Thus, using plasmonic nanoparticles in microscopy paves the way towards the development of non-toxic, highly sensitive, high resolution, photobleaching-free, and rapid biological sample imaging and tracking. In the following sections, we introduce the current demonstrations for plasmonic optical imaging based on various microscopy tools, which are performed in different schemes for anticipated biomedical applications.