Overview about the localization of nanoparticles in tissue and cellular context by different imaging techniques.

Anja Ostrowski,Sabrina Hadam,Lars Mundhenk,Martina C Meinke,Eckart Rühl,Daniel Nordmeyer,Achim D Gruber,Cornelia Holzhausen,Christina Graf,Ulrike Alexiev,Alexander Boreham,Annika Vogt,Jürgen Lademann

doi:10.3762/bjnano.6.25

Abstract

The increasing interest and recent developments in nanotechnology pose previously unparalleled challenges in understanding the effects of nanoparticles on living tissues. Despite significant progress in in vitro cell and tissue culture technologies, observations on particle distribution and tissue responses in whole organisms are still indispensable. In addition to a thorough understanding of complex tissue responses which is the domain of expert pathologists, the localization of particles at their sites of interaction with living structures is essential to complete the picture. In this review we will describe and compare different imaging techniques for localizing inorganic as well as organic nanoparticles in tissues, cells and subcellular compartments. The visualization techniques include well-established methods, such as standard light, fluorescence, transmission electron and scanning electron microscopy as well as more recent developments, such as light and electron microscopic autoradiography, fluorescence lifetime imaging, spectral imaging and linear unmixing, superresolution structured illumination, Raman microspectroscopy and X-ray microscopy. Importantly, all methodologies described allow for the simultaneous visualization of nanoparticles and evaluation of cell and tissue changes that are of prime interest for toxicopathologic studies. However, the different approaches vary in terms of applicability for specific particles, sensitivity, optical resolution, technical requirements and thus availability, and effects of labeling on particle properties. Specific bottle necks of each technology are discussed in detail. Interpretation of particle localization data from any of these techniques should therefore respect their specific merits and limitations as no single approach combines all desired properties.

Highlights

In the rapidly growing field of nanotechnology, recent developments have yielded a plethora of different nanoparticles (NP) with novel size-dependent properties that are very distinct from those of their bulk material [1,2]
We introduce and compare different imaging techniques for localizing inorganic NP like silica and iron oxide NP as well as organic NP such as polymer dendritic polyglycerol sulfates and chitosan NP
We describe well-established and widely used techniques, such as light, fluorescence, transmission electron and scanning electron microscopy which have already been reviewed by others from a different angle [20,34,35]

Summary

Introduction

In the rapidly growing field of nanotechnology, recent developments have yielded a plethora of different nanoparticles (NP) with novel size-dependent properties that are very distinct from those of their bulk material [1,2]. Or cryo-fixed tissue sections are often sputtercoated, i.e., covered with a thin layer of conductive material, for example, gold [176], to enhance the electrical conductivity of method need for labeling major advantages major disadvantages light microscopy in FFPE tissues depends on NP used easy, low cost, excellent evaluation of pathomorpholgic effects in context of NP detection limited resolution (above 200 nm), only for few NP species available as imaging technique, staining artifacts, specificity of staining protocols light and electron yes microscopic autoradiography highly sensitive and specific, excellent evaluation of pathomorphologic changes long exposure time of the sample, expensive, radioactive labeling, radiation safety requirements fluorescence microscopy yes, except for QD and UCNP

Results

Conclusion