Elizabeth Kathleen Neumann

Human hair provides a stable, noninvasive matrix for longitudinal chemical analysis but remains under-utilized because of challenges in sample preparation, reproducibility, and throughput. Here, we present an automated, high-throughput platform for mass spectrometry imaging analysis of single human hair strands. This workflow integrates robotic longitudinal sectioning with custom-designed microscope slides to enable consistent sample preparation with minimal user intervention. The method achieves 95% success rate of sectioning, and strong interlaboratory concordance. We demonstrate spatial mapping of endogenous lipids, metabolites, environmental contaminants, and pharmaceuticals across hair substructures, including the cortex and medulla. The platform enables temporal chemical profiling along the hair shaft and supports detection of both incorporated and exogenous compounds and establishes a scalable framework for biomarker discovery and forensic applications.

Understanding the stability of the active pharmaceutical ingredient (API) and drug−excipient interactions is critical for ensuring the efficacy and shelf life of pharmaceutical formulations. This study applies matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) to investigate two-dimensional (2D) and three-dimensional (3D) spatial profiling of degradants in Losartan potassium tablets that are subjected to temperature- and humidity-induced stress conditions. This approach allows for in situ visualization of API degradation and excipient compatibility within solid dosage forms. Upon stress, Losartan tablets formed dimeric and trimeric species as major degradation products. Spatial mapping revealed a gradual growth of these degradants from the control (T0) through four weeks of stress. Ion images showed distinct heterogeneity in the formation of dimer and trimer species across the tablet depth and plane; however, no preferential pattern was observed at the tablet periphery. The random distribution of degradants suggests that alongside humidity, localized microenvironments drive the degradation process. MALDI-MSI demonstrates strong potential as a high-throughput and sensitive alternative to traditional liquid chromatography-based procedures for early-stage formulation screening. Furthermore, this work suggests that when integrated with orthogonal techniques to coregister excipient domains, MALDI-MSI can serve as an emerging tool to uniquely characterize drug−excipient interactions during early-stage drug development. This provides spatially resolved insight that enhances accelerated stability assessment programs and streamline the selection of compatible excipients.

The human heart is characterized by aberrant lipid accumulation and remodeling during periods of stress and disease, yet spatially resolved lipidomic profiling of the human heart remains unreported. Here, we employ matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) to map lipid distributions across five anatomical regions of healthy human donor hearts (left and right atrium, left and right ventricle, and interventricular septum). Cryosections of donor hearts from healthy subjects were thaw-mounted onto indium tin oxide slides, coated with 2,5-dihydroxyacetophenone, and analyzed on a Bruker timsTOF fleX mass spectrometer in positive and negative ionization modes (m/z 50–1850; 20 μm raster spacing). Serial sections were stained with hematoxylin and eosin to enable histological coregistration with lipid distributions. We identified 150 unique lipid species across four glycerophospholipid classes, including phosphatidylcholine (PC), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), and phosphatidylserine (PS), with abundances and spatial distributions differing significantly between regions. H&E coregistration further resolved epicardial and myocardial compartments, enabling tissue-specific lipid mapping. These findings establish the first spatially resolved lipidomic profiles of the human heart and provide a framework for identifying region-specific lipid biomarkers of cardiovascular disease.

Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) is a powerful tool for mapping the spatial distribution of pharmaceuticals and metabolites in tissue. However, its effectiveness in the low-mass range (< 400 m/z) is impacted by matrix interference and ion suppression, reducing signal-to-noise (S/N) ratios. To address this challenge, we assessed a targeted quadrupole isolation strategy using a MALDI q-TOF mass spectrometer. This approach selectively isolates narrow windows around individual analytes m/z to reduce background noise and enhance S/N, therefore generating a smaller selective ion packet to the TOF analyzer. We applied this method to detect acetaminophen, paracetamol sulfate, caffeine, paraxanthine, as well as dopamine and its metabolites (HVA, 3-MT, and DOPAC) within murine liver and brain tissue sections, respectively. We utilized a range of isolation windows (e.g., 1, 5, 10, 20, 100 m/z) around each target m/z value. This dynamic isolation significantly decreased chemical background without fragmenting the target ions. As a result, we achieved precise spatial localization of parent drugs and their metabolites. Compared to untargeted acquisition, this method improved S/N by over 50% for all analytes within ≤10 m/z isolation ranges, while preserving tissue morphology. This targeted isolation approach extends the capabilities of MALDI MSI and offers a robust and scalable solution for analyzing low-mass xenobiotics and metabolites in situ.

Scope: To complete multiplex immunofluorescence on fresh frozen human tissue. Expected Outcome: Tissue sections that have been tagged with antibodies for imaging microscopy.

We investigated the spatial organization and heterogeneity of lipids across the healthy human heart to establish a regional metabolic framework. Using untargeted spatially resolved lipidomics with matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI), we identified distinct regional lipidomic signatures in cardiac regions. Our study challenges the assumption of metabolic uniformity and providing a framework for spatially targeted therapies and improved biomarker interpretation.

Hepatocellular carcinoma (HCC) is a common type of cancer with a high mortality rate, which is affected by the farnesoid X receptor (FXR) in the liver. FXR is a ligand-activated nuclear receptor involved in lipid metabolism and homeostasis. Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) enables spatially resolved molecular analysis and is particularly suited to profiling lipid distributions within tissues. In this study, MALDI MSI was employed to investigate alterations in liver lipid composition associated with HCC and FXR expression with a focus on phosphatidylcholine (PC) species. Distinct spatial and compositional differences in PC lipids were observed between HCC and nontumorous regions. Furthermore, we hypothesize a role of PC(38:4) in HCC based on cell culture experiments in which Hep3B cells were incubated in the presence of PC(38:4).

Polystyrene (PS), a widely used synthetic polymer, breaks into micro‐ and nanoscale particles that can enter the body and accumulate in tissues. Conventional methods provide bulk chemical information, but lack spatial and metabolic context. Here, we use matrix‐assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) with trapped ion mobility spectrometry (TIMS) to localize PS across whole‐body murine sections and individual organs, allowing differentiation of PS chain lengths and associated metabolic shifts. Oral PS exposure produced clear organ‐specific lipid remodeling. In the stomach, increases in phosphatidylcholine (PC(30:2)), phosphatidic acid (PA(36:1)), and sphingomyelin (SM(34:1; O ₂ )) suggest epithelial stress and barrier disruption. In the liver, PC(32:1) decreased, and higher PC(30:2) and PA(36:2) indicate impaired lipid export alongside compensatory adjustments to maintain membrane stability, with potential effects on systemic lipid balance. In the heart, reductions in SM(32:1; O ₂ ), ether‐linked phosphatidic acid (PA(O‐34:1)), and hexosylceramide (HexCer(30:1; O ₂ )) reflect disrupted sphingolipid and ether‐linked lipid species metabolism and altered lipid transport. Together, these findings reveal dynamic, tissue‐specific lipid responses to PS exposure. This study shows that MALDI TIMS MSI provides high‐resolution, label‐free mapping of PS and its metabolic footprint and can be extended to other low‐abundance synthetic compounds.

Polystyrene (PS), a widely used synthetic polymer, breaks into micro‐ and nanoscale particles that can enter the body and accumulate in tissues. Conventional methods provide bulk chemical information, but lack spatial and metabolic context. Here, we use matrix‐assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) with trapped ion mobility spectrometry (TIMS) to localize PS across whole‐body murine sections and individual organs, allowing differentiation of PS chain lengths and associated metabolic shifts. Oral PS exposure produced clear organ‐specific lipid remodeling. In the stomach, increases in phosphatidylcholine (PC(30:2)), phosphatidic acid (PA(36:1)), and sphingomyelin (SM(34:1; O ₂ )) suggest epithelial stress and barrier disruption. In the liver, PC(32:1) decreased, and higher PC(30:2) and PA(36:2) indicate impaired lipid export alongside compensatory adjustments to maintain membrane stability, with potential effects on systemic lipid balance. In the heart, reductions in SM(32:1; O ₂ ), ether‐linked phosphatidic acid (PA(O‐34:1)), and hexosylceramide (HexCer(30:1; O ₂ )) reflect disrupted sphingolipid and ether‐linked lipid species metabolism and altered lipid transport. Together, these findings reveal dynamic, tissue‐specific lipid responses to PS exposure. This study shows that MALDI TIMS MSI provides high‐resolution, label‐free mapping of PS and its metabolic footprint and can be extended to other low‐abundance synthetic compounds.