Boron‐Containing Probes for Non‐optical High‐Resolution Imaging of Biological Samples

Abstract

Boron has been employed in materials science as amarker for imaging specific structures by electron energy loss spectroscopy( EELS) or secondary ion mass spectrometry (SIMS). It has astrong potential in biological analyses as well; however,the specific coupling of asufficient number of boron atoms to abiological structure has proven challenging.Herein, we synthesizet ags containing closo-1,2-dicarbadodecaborane, coupled to soluble peptides,w hich were integrated in specific proteins by click chemistry in mammalian cells and were also coupled to nanobodies for use in immunocytochemistry experiments.T he tags were fully functional in biological samples,a sd emonstrated by nanoSIMS imaging of cell cultures.T he boron signal revealed the protein of interest, while other SIMS channelsw ere used for imaging different positive ions,such as the cellular metal ions.This allows,for the first time,the simultaneous imaging of such ions with aprotein of interest and will enable new biological applications in the SIMS field.

SIMS imaging in neurobiology and cell biology

“…Targeted imaging of specic cellular proteins by nanoSIMS has been demonstrated using newly developed labeling probes containing uorine 33 and boron. 34 For example, boron probes were used to label proteins of interest which then could be visualized by both nanoSIMS and uorescence microscopy. Successful imaging of the synaptic protein syntaxin 1 and mitochondrial marker TOM-70 in mammalian cells was carried out.…”

Subcellular Chemical Imaging: New Avenues in Cell Biology

“…lanthanides) have been utilized to image protein expression in human breast tumor tissue sections[67]. Recently, boron linked to proteins or to nanobodies binding to proteins have been used for simultaneous protein identification and elemental mapping by correlative fluorescence microscopy and nanoSIMS[68]. These studies suggest that exogenous elements with a small mass and size are suitable for probing DNA and proteins in the complex cellular environment and can be used in correlated nanoSIMS studies.Correlation between more than two subcellular imaging platforms.…”

Novel Secondary Ion Mass Spectrometry Methods for the Examination of Metabolic Effects at the Cellular and Subcellular Levels

“…For example, labels enriched with 19 F can be added to various proteins, which can then enable them to be analyzed both using NanoSIMS and using fluorescence imaging (Vreja et al, 2015 ). Similarly, areas of interest can be labeled by using boron-based probes, which then can be used to reveal the structure of proteins while other measurement channels can be used to examine other pertinent positive ions (Kabatas et al, 2019b ). These methods allow for more flexibility when designing SIMS experiments, and alleviate some of the limitations of the SIMS techniques.…”

“…This procedure is readily applied to cell cultures, where amino acids in the cell medium can be replaced easily with noncanonical ones but it is difficult to perform with animals. The ability of SIMS analyses to obtain information on the location of different structures without the use of these tools is a notable advantage of this method, although there are instances in which these labels can be used to enhance SIMS analysis (for example see Kabatas et al, 2015 , 2019a , b ; Vreja et al, 2015 ). These methods will be discussed in more detail later in this review article.…”