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bioRxiv · 10.1101/2024.03.20.585848

Cathodoluminescent and Characteristic X-ray-emissive Rare-Earth-doped Core/Shell Immunolabels for Spectromicroscopic Analysis of Cell Surface Receptors

Habermann, S.·Gerken, L. R. H.·Kociak, M.·Monachon, C.·Kissling, V. M.·Gogos, A.·Herrmann, I. K.
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Abstract

Understanding the localization and the interactions of biomolecules at the nanoscale and in the cellular context remains challenging. Electron microscopy (EM) as a non-Abbe limited technique gives access to the cellular ultra-structure yet results in grey-scale images and averts unambiguous (co-)localization of biomolecules. Multimodal nanoparticle-based immunolabels for correlative cathodoluminescence electron microscopy (CCLEM) and energy-dispersive X-ray spectromicroscopy (EDX-SM) are presented. The single-particle STEM-cathodoluminescence (CL) and characteristic X-ray emissivity of sub-20 nm lanthanide-doped nanoparticles were exploited as unique spectral fingerprints for precise localization and label identification. To maximize the nanoparticle brightness, lanthanides were incorporated in a low-phonon host lattice and separated from the environment using a passivating shell. The core/shell nanoparticles were then functionalized with either folic (terbium-doped) or caffeic acid (europium-doped). Their potential for immunolabeling was successfully demonstrated using HeLa cells expressing different surface receptors that bind to folic or caffeic acid, respectively. Both particle populations showed single-particle CL emission along with a distinctive energy-dispersive X-ray signal, with the latter enabling colour-based localization of receptors within swift imaging times well below 2 mins per {micro}m2 while offering high resolution with a pixel size of 2.78 nm. Taken together, these results open a route to color immunolabelling based on electron spectromicroscopy. Table of Contents O_FIG O_LINKSMALLFIG WIDTH=184 HEIGHT=200 SRC="FIGDIR/small/585848v1_ufig1.gif" ALT="Figure 1"> View larger version (74K): org.highwire.dtl.DTLVardef@1f7c2d3org.highwire.dtl.DTLVardef@117be1eorg.highwire.dtl.DTLVardef@1c2bab2org.highwire.dtl.DTLVardef@16f3677_HPS_FORMAT_FIGEXP M_FIG Small (sub-20 nm) lanthanide-doped nanoparticles were successfully utilized in electron microscopy to label biological structures and contextualize them in the cells ultrastructure. Leveraging unique energy-dispersive X-ray signatures, the nanoparticles location and doping-identity was easily and fast retrieved, demonstrating the methods potential to (co)-localize labels while supplying a holistic impression of the underlying processes, as entire cells could be mapped. C_FIG

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Habermann, S., Gerken, L. R. H., Kociak, M., Monachon, C., Kissling, V. M., Gogos, A., Herrmann, I. K.. 2024-03-23. Cathodoluminescent and Characteristic X-ray-emissive Rare-Earth-doped Core/Shell Immunolabels for Spectromicroscopic Analysis of Cell Surface Receptors. https://doi.org/10.1101/2024.03.20.585848

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