Imaging of nanoparticle dynamics in live and apoptotic cells using temporally-modulated polarization

Omer Wagner,Rinat Meir,Hagay Shpaisman,Amihai Meiri,Eli Sloutskin,Moty Schultz,Eran Barnoy,Eitan Edri,Zeev Zalevsky

doi:10.1038/s41598-018-38375-9

Abstract

Gold nanoparticles are widely exploited in phototherapy. Owing to their biocompatibility and their strong visible-light surface plasmonic resonance, these particles also serve as contrast agents for cell image enhancement and super-resolved imaging. Yet, their optical signal is still insufficiently strong for many important real-life applications. Also, the differentiation between adjacent nanoparticles is usually limited by the optical resolution and the orientations of non-spherical particles are unknown. These limitations hamper the progress in cell research by direct optical microscopy and narrow the range of phototherapy applications. Here we demonstrate exploiting the optical anisotropy of non-spherical nanoparticles to achieve super-resolution in live cell imaging and to resolve the intracellular nanoparticle orientations. In particular, by modulating the light polarization and taking advantage of the polarization-dependence of gold nanorod optical properties, we realize the ‘lock-in amplification’, widely-used in electronic engineering, to achieve image enhancement in live cells and in cells that undergo apoptotic changes.

Highlights

Biomarkers and contrast agents are frequently used in current day imaging to mark specific locations, increase the imaging signal and maximize the signal to noise ratio (SNR)[1]
To test the validity of the polarization-modulated lock-in imaging (PMLI) method, we first employ it for the optical visualization of a few individual gold nanorod (GNR) dispersed on a cover slip
The BF is typically less efficient than the DF in terms of the SNR, the BF imaging depends on light absorbance, rather than scattering, potentially providing an additional sample characterization

Summary

Introduction

Biomarkers and contrast agents are frequently used in current day imaging to mark specific locations, increase the imaging signal and maximize the signal to noise ratio (SNR)[1]. The existing experimental methods do not allow the unstained cellular compartments to be imaged in real life, with a high resolution, in parallel with the detection of nanoparticle positions and orientations. The development of such methods should provide a deeper and more detailed understanding of the apoptosis, as of many other vital biological processes. Background reduction by hyperspectral imaging[21,22], marker fluorescence or Raman response enhancement by SPR23,24, intensity-modulated GNP flickering[25], and several other methods were employed Most of these approaches require dedicated sophisticated and expensive equipment. The simplest GNPs with an anisotropic SPR are the gold nanorods

Methods

Results

Conclusion