Current Status of Domestic Mass Spectrometry Imaging Sources: Case Studies on the Adaptation of Atmospheric-Pressure In-Situ MSI

In recent years, domestically produced mass spectrometry imaging sources have gradually been implemented along the ‘atmospheric pressure, in situ, matrix-free’ approach, moving beyond mere theoretical concepts in academic papers. Represented by Neo Source INSTRUMENT’s MSI DPI and MSI LDPI, these add-on imaging sources directly convert existing mass spectrometers into imaging platforms, delivering reproducible results across multiple real-world scenarios. This article shares several representative application case studies.

Technical characteristics: ambient pressure, in situ, matrix-free

A clear focus of domestically produced imaging sources is to minimise the burden of sample preparation. The MSI DPI employs a dual-mode DESI/PI approach, performing desorption and ionisation under ambient pressure conditions, with no matrix required and zero pre-treatment throughout the process; the MSI LDPI, meanwhile, achieves spatial resolution of 2–3 μm, also without the need for a matrix. This significantly reduces the workflow that would otherwise require freeze-drying, sectioning and matrix spraying, allowing samples to remain closer to their original state.

Case Study 1: Spatial Distribution of Flavour Compounds in Tea Leaves

Tea research often focuses on the spatial distribution of components such as catechins, caffeine and L-theanine within tea leaves. Direct imaging of tea samples using MSI DPI enables the generation of surface distribution maps for these components without the need for a matrix. In validated comparisons, post-electron ionisation enhanced the L-theanine signal by approximately 14.5-fold and the caffeine signal by approximately 61-fold (approximately 60-fold). This means that signals which were originally weak under conventional DESI become clearly distinguishable in dual-mode analysis.

Case Study 2: Localisation of Contaminants in Olive Oil

Olive oil quality testing focuses on the spatial heterogeneity of contaminants such as pesticide residues and oxidation products. Traditional homogenised analysis can only provide ‘average values’ and fails to reveal whether contaminants are locally concentrated within the oil. MSI DPI’s matrix-free imaging preserves the sample’s in situ information, directly marking the locations of contaminants on the image, which provides greater value for traceability and grading.

Case Study 3: High-amplitude cholesterol signals in rat brains

In neuroscience research, the spatial distribution of lipids such as cholesterol is a hot topic. The post-photoionisation channel of MSI DPI is well-suited to such non-polar species; in validated samples, the cholesterol signal in mouse brain tissue was amplified by approximately 205-fold. This high gain allows even faintly distributed lipids to be visualised in the images, reducing false negatives caused by insufficient signal.

Case Study 4: Subtle Gradients in High-Resolution Scenarios

For research requiring the observation of gradients at the cellular level, the 2–3 μm resolution of MSI LDPI offers finer resolution capabilities, with a minimum detectable m/z of approximately 70, making it suitable for examining concentration changes of molecules within minute areas. Such scenarios are commonly found in studies requiring high spatial resolution, such as at the boundaries of brain regions or tissue junctions.

Industry Perspective: A Differentiated Strategy to Capture Niche Scenarios

Market progress for domestically produced imaging sources stems more from a differentiated combination of ‘compatibility + matrix-free + gradient resolution’ than from a simple competition on a single parameter. This enables laboratories with existing instruments to acquire imaging capabilities at a lower threshold, whilst also solidifying the advantages of ambient pressure in situ analysis on real samples. Whether this approach can be sustained depends on the ability to consistently produce reproducible imaging results within each specific application.

Summary

The current state of domestically produced mass spectrometry imaging sources involves a modification approach utilising ambient pressure in situ and matrix-free techniques to deliver reproducible results on real samples such as tea leaves, olive oil and neural tissue. The case of New Source’s MSI DPI / LDPI demonstrates that retrofittable imaging sources are no longer merely alternative solutions, but stand-alone tools in specific application scenarios.