Three-dimensional (3D) imaging of lipids in skin tissues with infrared matrix-assisted laser desorption electrospray ionization (MALDESI) mass spectrometry

Abstract

Three-dimensional (3D) mass spectrometry imaging (MSI) has become a growing frontier as it has the potential to provide a 3D representation of analytes in a label-free, untargeted, and chemically specific manner. The most common 3D MSI is accomplished by the reconstruction of 2D MSI from serial cryosections; however, this presents significant challenges in image alignment and registration. An alternative method would be to sequentially image a sample by consecutive ablation events to create a 3D image. In this study, we describe the use of infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) in ablation-based 3D MSI for analyses of lipids within fresh frozen skin tissue. Depth resolution using different laser energy levels was explored with a confocal laser scanning microscope to establish the imaging parameters for skin. The lowest and highest laser energy level resulted in a depth resolution of 7 μm and 18 μm, respectively. A total of 594 lipids were putatively detected and detailed lipid profiles across different skin layers were revealed in a 56-layer 3D imaging experiment. Correlated with histological information, the skin structure was characterized with differential lipid distributions with a lateral resolution of 50 μm and a z resolution of 7 μm.

Vitamin D deficiency promotes accumulation of bioactive lipids and increased endocannabinoid tone in zebrafish

“…Of note, various ammonium adducts were observed, particularly for neutral lipids, although a source of ammonium was not added. Many of these ammonium adducts have been previously reported, including those of triglycerides, using the same or similar ionization methods ( 47 , 48 , 49 , 50 ). Two possible theories for these adducts are given by Zhou et al.…”

“…Many of these ammonium adducts have been previously reported, including those of triglycerides, using the same or similar ionization methods. 48,49,50,51 Two possible theories for these adducts are given by Zhou et al…”

Recent Advances of Ambient Mass Spectrometry Imaging and Its Applications in Lipid and Metabolite Analysis

“…Compared to an organic matrix, water and ice can reduce the interference caused by an organic matrix at a low-mass range, which has great advantages in the analysis of small compounds, especially lipids and metabolites. The MALDESI and IR-MALDESI-MSI techniques have been applied to map the distribution of compounds in the mouse bones [50], cherry tomatoes [51], cancerous hen ovarian tissues [52], skin tissues [53], over-the-counter pharmaceuticals [54], 3D imaging [54] and lipid and metabolites analysis [55]. Recently, Lee et al developed a new ambient ion source named laser desorption/ionization droplet delivery (LDIDD) with a high resolution (2.4 to 3 µm) by using 266 nm UV laser beams (Figure 3D) [56].…”

Enhancing Metabolomic Coverage in Positive Ionization Mode Using Dicationic Reagents by Infrared Matrix-Assisted Laser Desorption Electrospray Ionization

“…The current IR-MALDESI source is interfaced with an Orbitrap Exploris 240 mass spectrometer. Over the past decade, IR-MALDESI has advanced significantly in the direct analysis as well as spatially resolved mass spectrometry imaging of biomolecules, including metabolites and lipids [9,29].…”