Bright sub-20 nm cathodoluminescent nanoprobes for multicolor electron microscopy

TL;DR

This paper introduces sub-20 nm lanthanide-doped nanoprobes that emit cathodoluminescence for multicolor electron microscopy, enabling high-resolution localization of biomolecules within cells.

Contribution

It presents a novel multicolor EM labeling technology using luminescent nanoprobes with potential for sub-20 nm resolution and nine distinct spectral signatures.

Findings

Nanoprobes emit narrow spectral lines for nine colors.

Potential for sub-20 nm resolution in biomolecule localization.

Optimized synthesis and imaging conditions enhance signal-to-noise ratio.

Abstract

Electron microscopy (EM) has been instrumental in our understanding of biological systems ranging from subcellular structures to complex organisms. Although EM reveals cellular morphology with nanoscale resolution, it does not provide information on the location of proteins within a cellular context. An EM-based bioimaging technology capable of localizing individual proteins and resolving protein-protein interactions with respect to cellular ultrastructure would provide important insights into the molecular biology of a cell. Here, we report on the development of luminescent nanoprobes potentially suitable for labeling biomolecules in a multicolor EM modality. In this approach, the labels are based on lanthanide-doped nanoparticles that emit light under electron excitation in a process known as cathodoluminescence (CL). Our results suggest that the optimization of nanoparticle composition, synthesis protocols and electron imaging conditions could enable high signal-to-noise localization of biomolecules with a sub-20-nm resolution, limited only by the nanoparticle size. In ensemble measurements, these luminescent labels exhibit narrow spectra of nine distinct colors that are characteristic of the corresponding rare-earth dopant type.