High Axial and Lateral Resolutions on Self-Assembled Gold Nanoparticle Metasurfaces for Live-Cell Imaging

Abstract

A plasmonic metasurface composed of homogeneously self-assembled gold nanoparticles can provide high-contrast fluorescence images confined to the nanointerface. In this study, we successfully demonstrated real-time, high-spatiotemporal-resolution imaging of adhered Venus-paxillin-3T3 live cells under a widefield microscope, where not only a high axial resolution but also a high lateral resolution down to the theoretical limit were confirmed through nascent cluster formation of paxillin. The improved lateral resolution on the sheet could be interpreted as the characteristic of localized surface plasmon resonance (LSPR)mediated enhanced fluorescence and the metasurface acting as a nanothickness plane light emitter. We also found minimized photobleaching, owing to the increase in the emission efficiency via plasmon-exciton coupling. This simple nanomaterial-based technique will be a powerful tool to enhance interfacial signals and improve the quality of live-cell images, not only under widefield microscopes but also in combination with various super-resolution microscope systems in the future.

Transient Nascent Adhesion at the Initial Stage of Cell Adhesion Visualized on a Plasmonic Metasurface

“…The plasmonic metasurface-mediated imaging allows for live-cell imaging with high spatial resolutions even during cell movement due to the properties of the metasurface, which has an extremely high refractive index and acts as a nanothickness plane light emitter. [33] We also found that the plasmonic metasurface minimizes photobleaching owing to the increase in the emission efficiency via plasmon-exciton coupling, which is an important advantage for maintaining high contrast and resolution in long-term live-cell imaging. [33] Previous studies observed matured FAs of well spread cells after overnight incubation in order to establish the methodology for live-cell imaging using our plasmonic metasurface.…”

“…[33] We also found that the plasmonic metasurface minimizes photobleaching owing to the increase in the emission efficiency via plasmon-exciton coupling, which is an important advantage for maintaining high contrast and resolution in long-term live-cell imaging. [33] Previous studies observed matured FAs of well spread cells after overnight incubation in order to establish the methodology for live-cell imaging using our plasmonic metasurface. Taking advantages of our plasmonic metasurface-mediated imaging technique such as high spatial resolution and minimal photobleaching, we apply our imaging technique to observe initial cell adhesion behavior where cells start to adhere through weak and unstable interactions susceptible for photobleaching.…”

“…Self-assembled monolayers (SAMs) composed of oleylaminecoated gold nanoparticles (AuOAs) with a diameter of 11.8 AE 1.4 nm were fabricated in a LangmuirÀBlodgett (LB) trough. [33] The self-assembly process of AuOAs at the air-water interface, from the evaporation of toluene to solid-like domain formation, is described in Figure S1 and Video S1, Supporting Information. The solid-like domains were gathered together by Teflon bars and compressed until the surface pressure (Π) reached 15 mN m À1 (Figure 1a) and then transferred onto a hydrophobized glass coverslip via the LangmuirÀSchaefer (LS) method.…”

“…The fluorescence imaging technique that we recently developed and utilized in this study is based on a plasmonic metasurface composed of self-assembled gold nanoparticles (NPs). [32,33] A self-assembled monolayer of homogeneously sized NPs was fabricated at the airÀwater interface and transferred onto a coverslip. Compared with other super-resolution microscopy techniques, our plasmonic metasurface-mediated imaging technique is extremely simple but highly effective for monitoring fast molecular-level dynamics at a nanointerface.…”

“…The localized surface plasmon resonance (LSPR) of the plasmonic metasurface provides high-contrast interfacial images due to the light confined within a few tens of nanometers from the particles and the enhancement of fluorescence. [32] That improves lateral resolution reaching to the theoretical limit (a lateral resolution of a few pixels, with one pixel equivalent to 65 nm, as estimated by size of resolved bright spots [33] ) and an axial resolution of %20 nm (estimated by exponential decay of LSPR field from finite-difference time-domain [FDTD] simulation [32] ). The plasmonic metasurface-mediated imaging allows for live-cell imaging with high spatial resolutions even during cell movement due to the properties of the metasurface, which has an extremely high refractive index and acts as a nanothickness plane light emitter.…”