MSACL 2025 Abstract

Boronic Acid Mass Tags for the Specific Detection and Imaging of Diol Compounds

Justine Gatein, Nassim Maarouf Mesli, William D. Lubell, Pierre Chaurand
Université de Montréal, Montréal, CA

Justine Gatein (Presenter) Université de Montréal >> POSTER (PDF)

Presenter Bio: I am a PhD candidate in analytical chemistry at the Université de Montréal, where I develop MALDI-based mass spectrometry imaging (MSI) approaches for the spatial characterization of biological tissues. My doctoral research, conducted in Prof. Pierre Chaurand's laboratory, focuses on small molecule analysis and methodological development for tissue imaging applications, to understand metabolic reprogramming in cancer.
I am also completing a PharmD thesis at the Université Paul Sabatier (Toulouse III) under the supervision of Dr. Anthony Lemarié. This work explores the contribution of MSI to the understanding of tumoral mechanisms and the identification of novel therapeutic targets in glioblastoma.
Prior to my doctoral studies, I completed a Master's degree in analytical chemistry for drugs and natural products at the Université de Bordeaux in a work-study program at Sanofi, where I was involved in analytical method comparison and validation, supplier qualification, and pharmacopoeial monograph updates. My background originates in pharmaceutical sciences, at the Université Paul Sabatier (Toulouse III), with clinical training in pharmacokinetics and therapeutic drug monitoring at the CHU de Toulouse.

Relevant Financial Disclosures (within past 24 months, reported on May 01, 2026) No relevant financial relationship(s) to disclose. Conflict mitigation NOT REQUIRED.

INTRODUCTION
The advancement of on-tissue chemical derivatization techniques for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) of endogenous metabolites in tissues has attracted significant interest due to their benefits in enhancing detection sensitivity and ionization efficiency for poorly ionizable or/and low-abundance metabolites. Among these, glucose was found of high interest because of its implication in numerous diseases. The boron group of boronic acids exhibits high reactivity with compounds containing a diol function. Chemical derivatization enables the selective targeting of diols while enhancing the sensitivity and specificity of the method while reducing background noise, leading to more precise and reliable analysis.

METHODS
A new boronic acid containing a positively charged amine function was developed to compensate for the low ionization efficiency of compounds and enhance their detection in MSI. The analyte to tag ratio that allows for a complete reaction in solution and detection yield was first optimized. For MALDI MS of the 4-hydroxyestrone adduct, the best matrix was 9-aminoacridine (9AA) and it was 2′,6′-dihydroxyacetophenone (DHA) for the glucose adduct. For glucose, using brain homogenates, an optimized solution of 5mg/ml of boronic acid in 50% methanol was used to determine the best on-tissue reaction. Spray deposition parameters were then optimized for the boronic acid tag and DHA matrix. MALDI MSI was subsequently performed in the positive ion mode. Since the boron group has an easily recognizable isotopic signature, it is possible to more precisely identify the adducts that have reacted with the tag, in addition to confirming their identification by exact mass. For direct MALDI MSI glucose detection, N-(1-naphthyl) ethylenediamine dinitrate (NEDC) matrix was also spray deposited on all sections. MALDI MSI was then performed in the negative ion mode.

RESULTS
Boronic acid reactivity was initially tested in solution using several diol standards including 4-hydroxyestrone, ascorbic acid and several hexoses. In particular, we were able to successfully derivatize glucose in solution. After optimizing the reaction conditions (tag quantity, solvent, etc.), several matrices including 9AA, 1,5-dihydroxybenzoic acid, 1,5-diaminonaphthalene and DHA, were tested using the dry droplet method. For MALDI MSI, the tag and the matrix spray deposition method then were optimized. Thin tissue sections from mouse brain homogenates and different mouse organs were analyzed using the optimized methods using a Shimadzu MALDI iMScopeQT system. For glucose, the results were compared with MALDI MSI methods previously reported in the literature.
Glucose was successfully detected in liver, kidney, testis and brain tissue sections (12 µm thick) by MALDI MSI at a spatial resolution of 25 µm using NEDC as matrix ([glucose + Cl]⁻, m/z = 215.032) and after on-tissue chemical derivatization with boronic acid ([glucose-boronic ac]+, m/z = 401.1868) using DHA as matrix with a mass accuracy ~1ppm. For liver and testis, glucose was homogenously detected across the sections. For brain, in all cases glucose was successfully detected predominantly in the gray matter. This distribution is consistent with that previously described in the literature, as the gray matter is the site of intense metabolic activity. For kidney, glucose was mostly detected in the medulla, which is again consistent with that previously described in the literature. However, when comparing glucose signal intensities between the ([glucose + Cl]⁻ NEDC produced ions and the ([glucose-boronic ac]+ ions, for brain, on-tissue chemical derivatization proved to be more sensitive by ~600-fold, while for liver, testis and kidney tissue, the detection improvements were ~800-fold, ~200-fold and ~70-fold, respectively.

CONCLUSION
As glucose metabolism is severely altered in many diseases, the development of MSI-based analytical methods is necessary to better understand local metabolism and potentially identify new therapeutic targets to increase treatment efficiency. By providing spatially resolved metabolic information, these methods offer valuable insights into disease-specific metabolic reprogramming and may contribute to the development of more effective, targeted therapeutic interventions.