Fig. 1: Outline of the review with separate strands for sensing (bulk assays) and imaging (single particles).
From: Nanophotonic sensing and label-free imaging of extracellular vesicles
a Nanophotonic sensing of bulk analytes. (i) General schematic of biosensing based on evanescent waves. (ii) Examples of resonant metasurfaces, including plasmonic nanohole arrays (left) and dielectric nanohole arrays (right, shown in a ‘chirped’ configuration). (iii) The readout can take many forms, such as spectral or intensity-based approaches. We limit this review to imaging-based sensing. Images are adapted from25,44,106,107. b Single particle imaging using fluorescence microscopy. Resonant surfaces can be used to enhance fluorescent signals from single particles. Subfigures rearranged and taken from92. c Label-free imaging. (i) Interferometric scattering microscopy (iScat) can detect single particles without labels. (ii) Resonant metasurfaces are used for surface-enhanced iScat. Images are from108,109. Ab, antibody; PEG, polyethylene glycol; iPSF, interferometric point spread function; CCD, charge-coupled device
