Simultaneous detection of phosphatidylcholines and glycerolipids using matrix‐enhanced surface‐assisted laser desorption/ionization‐mass spectrometry with sputter‐deposited platinum film

Abstract

Matrix-assisted laser desorption/ionisation (MALDI) imaging mass spectrometry (IMS) allows for the simultaneous detection and imaging of several molecules in brain tissue. However, the detection of glycerolipids such as diacylglycerol (DAG) and triacylglycerol (TAG) in brain tissues is hindered in MALDI-IMS because of the ion suppression effect from excessive ion yields of phosphatidylcholine (PC). In this study, we describe an approach that employs a homogeneously deposited metal nanoparticle layer (or film) for the detection of glycerolipids in rat brain tissue sections using IMS. Surface-assisted laser desorption/ionisation IMS with sputter-deposited Pt film (Pt-SALDI-IMS) for lipid analysis was performed as a solvent-free and organic matrix-free method. Pt-SALDI produced a homogenous layer of nanoparticles over the surface of the rat brain tissue section. Highly selective detection of lipids was possible by MALDI-IMS and Pt-SALDI-IMS; MALDI-IMS detected the dominant ion peak of PC in the tissue section, and there were no ion peaks representing glycerolipids such as DAG and TAG. In contrast, Pt-SALDI-IMS allowed the detection of these glycerolipids, but not PC. Therefore, using a hybrid method combining MALDI and Pt-SALDI (i.e., matrix-enhanced [ME]-Pt-SALDI-IMS), we achieved the simultaneous detection of PC, PE and DAG in rat brain tissue sections, and the sensitivity for the detection of these molecules was better than that of MALDI-IMS or Pt-SALDI alone. The present simple ME-Pt-SALDI approach for the simultaneous detection of PC and DAG using two matrices (sputter-deposited Pt film and DHB matrix) would be useful in imaging analyses of biological tissue sections.

Porous silicon mass spectrometry as an alternative confirmatory assay for compliance testing of methadone

“…A prominent compound detected as its protonated ion of m/z 184 in plasma was assigned, through MS/MS, to correspond to phosphocholine, a lipid headgroup (Figure S8). This compound has been noted in the literature as an abundant head group fragment ion formed in SALDI‐MS, originating from biological tissue in general and especially red blood cells when fragmented …”

“…This compound has been noted in the literature as an abundant head group fragment ion formed in SALDI-MS, originating from biological tissue in general and especially red blood cells when fragmented. [23,24] A key disadvantage of some analytical techniques is the requirement of large sample volumes, which can be in excess of 1 mL per replicate. [25] In order to use the lowest volume possible, the saliva to chloroform ratio was optimized using saliva volumes ranging from 50 to 300 μL with a methadone concentration of 100 ng/mL, against a constant chloroform volume of 40 μL (Figure 4).…”

Novel approach to enhance sensitivity in surface‐assisted laser desorption/ionization mass spectrometry imaging using deposited organic‐inorganic hybrid matrices

“…As it was difficult to distinguish the intensity of Na + adducts of glutathione from background, these data were not examined further. The ion intensity of K + adducts of Di‐C16:0‐DAG and Di‐C18:1‐DAG, reported to have high detection sensitivity using Pt‐SALDI, was highest using method D. In contrast, the ion intensity was low using methods B and E, which did not use Zr sputtering, and method A, which used Zr sputtering alone (Figure S3c,d).…”

“…Although several metals have been used in the SALDI method, metal complexes cannot form from the generated ions unlike for gold (Au) or silver (Ag) in the use of platinum (Pt) . An ME‐SALDI method using MALDI matrix and Pt film can reportedly detect diacylglycerol lipids that were difficult to detect using conventional MALDI methods …”

Nanomaterials as Assisted Matrix of Laser Desorption/Ionization Time-of-Flight Mass Spectrometry for the Analysis of Small Molecules

“…Among various metal-or metal oxide-based nanomaterials (e.g., Au [51,52,53,54,55], Ag [56], Pt [57,58,59], TiO 2 [60,61,62], ZnO [63], CdS [64], and HgTe [65] NPs) that explored as matrices for LDI-TOF MS, TiO 2 and gold NPs (Au NPs) attracted much more attention because their intrinsic advantages, such as large surface area, strong absorption efficiency in UV-visible region, high chemical stability, easy modification and preparation.…”