Imaging of Lipids in Native Human Bone Sections Using TOF–Secondary Ion Mass Spectrometry, Atmospheric Pressure Scanning Microprobe Matrix-Assisted Laser Desorption/Ionization Orbitrap Mass Spectrometry, and Orbitrap–Secondary Ion Mass Spectrometry

Abstract

A method is described for high-resolution label-free molecular imaging of human bone tissue. To preserve the lipid content and the heterogeneous structure of osseous tissue, 4 μm thick human bone sections were prepared via cryoembedding and tape-assisted cryosectioning, circumventing the application of organic solvents and a decalcification step. A protocol for comparative mass spectrometry imaging (MSI) on the same section was established for initial analysis with time-of-flight secondary ion mass spectrometry (TOF-SIMS) at a lateral resolution of 10 μm to <500 nm, followed by atmospheric pressure scanning microprobe matrix-assisted laser desorption/ionization (AP-SMALDI) Orbitrap MSI at a lateral resolution of 10 μm. This procedure ultimately enabled MSI of lipids, providing the lateral localization of major lipid classes such as glycero-, glycerophospho-, and sphingolipids. Additionally, the applicability of the recently emerged Orbitrap-TOF-SIMS hybrid system was exemplarily examined and compared to the before-mentioned MSI methods.

Sample preparation of bone tissue for MALDI-MSI for forensic and (pre)clinical applications

“…For calcified tissues, like bone, decalcification is often performed to allow for easier sectioning and to reduce insulating properties of the sample, but more over to remove the unwanted background signal in MALDI-MSI caused by the mineral structure of these tissues [6]. These procedures, however, pose a high risk of contamination and analyte delocalization [7]. Despite the wide range of tissues that have been studied using MALDI-MSI, there are only a few studies that apply this technique on skeletal tissue [7][8][9][10][11].…”

“…These procedures, however, pose a high risk of contamination and analyte delocalization [7]. Despite the wide range of tissues that have been studied using MALDI-MSI, there are only a few studies that apply this technique on skeletal tissue [7][8][9][10][11]. This can be explained by the absence of proper section preparation protocols for undecalcified bone tissue.…”

“…Undecalcified bone tissue is preferred to avoid solvent-induced analyte delocalization, which better preserves the in vivo distribution. The lack of existing sample preparation protocols can be explained by the complex morphology of bone tissue [7,9,11]. The combination of hard (bone), stiff (cartilage, tendons, skeletal muscle), and rather soft tissue (bone marrow, surrounding periosteum, smooth muscle) in the skeletal tissue makes sectioning a challenge [7,11].…”

METASPACE: A community-populated knowledge base of spatial metabolomes in health and disease

“…We illustrated how METASPACE facilitates metabolite annotation for imaging MS, reveals the state of the art of the imaging MS technology, enables large-scale analysis of spatial metabolomes, and supports drug development. METASPACE, although not yet published, was already used in several publications [37][38][39][40][41][42][43] and highlighted in numerous reviews that indicates the significance and uniqueness of this resource for the imaging MS field. With the current rate of growth of 1000 datasets a year, its molecular and biological coverage will soon increase enough to provide spatial metabolomics atlases for various tissues, organs, and organisms.…”

Identification of nanoparticles and their localization in algal biofilm by 3D-imaging secondary ion mass spectrometry

“…53 The C 16 H 31 O 2 À secondary ion (m/z 255) has already been reported to originate from a lipid side chain of palmitic acid aer deprotonation. 15,54 Ti-containing secondary ions were identied in the mass spectrum by the clear isotopic pattern of titanium (refer to Fig. 4B and C).…”