MALDI-IMS Lipidomics

Matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) is a two-dimensional MALDI-MS technique used to analyze and visualize the spatial distribution of biomolecules. Since the technology was introduced, it has quickly spread and developed because of its enormous potential. There are many kinds of lipids and their structures are very complex, so the analysis of lipids is full of difficulties and challenges. MALDI-IMS technology can not only identify lipids in direct biological samples, but also image the spatial distribution of analytes. In recent years, the technology has been widely used in the study of lipidomics. Alfa Chemistry can offer quality MALDI-IMS lipidomics service for analysis thousands of lipids. The results provide a histological map of lipid biomolecules based on mass/charge ratio (m/z) localization and identification, and the imaging data can be normalized to total ion currents to calculate lipid abundance and can also be used for statistical tests.

Alfa Chemistry's Workflow

The complete analytical procedure of MALDI-IMS lipidomics in Alfa Chemistry is described as shown in Fig.1 ^[1].

Fig.1 The analytical procedure of MALDI-IMS lipidomics

In MALDI-IMS, sample preparation is a very critical step, which is directly related to the quality of imaging and the type and quantity of detected substances. Sample preparation mainly includes tissue slice preparation, pretreatment, matrix selection and matrix spray selection, etc. Alfa Chemistry has various way to deal with these processes.

• Tissue slice preparation: The tissue samples are frozen (−80 °C) after surgical separation or dissection and sliced in a −20 to −25 °C cryostat to maintain the integrity and spatial organization of the biomolecules in samples.
• Pretreatment: Different solvents are used to wash tissue slices, or the enzymatic hydrolysis is adopted to remove the interference, or the derivatization method is used in low content of lipid molecules to enhance the detection signal strength to achieve specific detection of a certain type of lipid.
• Matrix selection: There are many substrates to choose in Alfa Chemistry according to the actual situation, such as organic small molecule matrix, ionic liquid matrix and inorganic nanomaterial matrix, etc. The acidic matrix is suitable for positive ion mode, and neutral or alkaline matrix is suitable for negative ion mode.
• Matrix spray: At present, the matrix spraying methods commonly used in Alfa Chemistry mainly fall into three categories according to different mechanisms: (1) spray gun method, (2) sublimation method and (3) automatic spray method. Each method has its own advantages. We will choose the suitable method according to the actual situation of the sample.

Instrument Platform

Alfa Chemistry has state of-the-art time of flight mass spectrometer (TOF-MS) instrument for MALDI-IMS. The instrument shows high accuracy and resolving power and allow the separation of ionized accelerated molecules according to their mass-to-charge ratio (m/z). In addition, the hybrid analyzers pairing various technologies with TOF are also introduced in our laboratory: a quadrupole mass analyzer and TOF, a quadrupole ion trap and TOF, an ion mobility spectrometer and TOF, and tandem TOF mass spectrometers, to further improve the analytical ability of TOF-MS.

Advantages of MALDI-IMS

• High-throughput and one-shot imaging enables the analysis of multiple substances in a sample.
• In situ analysis.
• Fouling resistant. The technique uses a MALDI ionization source, which allows direct analysis of biological tissue samples with high salinity.
• Directly visualize the spatial distribution of biomolecules without extraction, purification, separation, or labeling of biological samples.

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Reference

1. Müller W. H., et al. Imaging lipids in biological samples with surface-assisted laser desorption/ionization mass spectrometry: A concise review of the last decade[J]. Progress in Lipid Research, 2021, 83: 101114.