Targeted Nanodiamonds for Identification of Subcellular Protein Assemblies in Mammalian Cells

TL;DR

This study demonstrates the use of nanodiamonds as targeted contrast labels for TEM to identify subcellular protein assemblies in live mammalian cells, enabling precise localization and identification within cellular environments.

Contribution

It introduces nanodiamonds as novel labels for nanoscale TEM imaging of subcellular structures, combining targeted delivery, unambiguous identification, and potential for correlated optical/electron bioimaging.

Findings

Nanodiamonds can be efficiently targeted to specific cellular structures.

Distinct TEM signatures allow unambiguous nanodiamond identification.

First use of nanodiamonds as labels for subcellular protein assemblies in TEM.

Abstract

Transmission electron microscopy (TEM) can be used to successfully determine the structures of proteins. However, such studies are typically done ex situ after extraction of the protein from the cellular environment. Here we describe an application for nanodiamonds as targeted intensity contrast labels in biological TEM, using the nuclear pore complex (NPC) as a model macroassembly. We demonstrate that delivery of antibody-conjugated nanodiamonds to live mammalian cells using maltotriose-conjugated polypropylenimine dendrimers results in efficient localization of nanodiamonds to the intended cellular target. We further identify signatures of nanodiamonds under TEM that allow for unambiguous identification of individual nanodiamonds from a resin-embedded, OsO4-stained environment. This is the first demonstration of nanodiamonds as labels for nanoscale TEM-based identification of subcellular protein assemblies. These results, combined with the unique fluorescence properties and biocompatibility of nanodiamonds, represent an important step toward the use of nanodiamonds as markers for correlated optical/electron bioimaging.