Imaging Capabilities of a Low-Cost Benchtop MALDI-TOF Mass Spectrometer

Significance of the Topic

Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) enables spatial mapping of biomolecules in tissues, offering insights into molecular distributions underlying physiological and pathological processes. The adaptation of this technique to a low-cost benchtop MALDI-TOF instrument broadens accessibility, supporting applications in research, quality control, and education.

Objectives and Study Overview

This study assesses the imaging performance of a Shimadzu MALDI-8020 benchtop linear TOF mass spectrometer for lipid, peptide, and intact protein analysis in rat brain tissue. It transfers established on-tissue digestion and protein imaging protocols from a MALDI-7090 TOF-TOF system to the compact platform and evaluates its capability to detect and localize biomolecules up to 22 kDa.

Methodology

Sagittal sections of rat brain were mounted on ITO slides and subjected to a six-step solvent wash to remove salts and lipids. Samples were divided for on-tissue digestion or intact protein imaging. Porcine trypsin and CHCA matrix were applied for peptide generation, while sinapinic acid was used for intact proteins. Matrices were deposited using SunCollect and IMLayer AERO sprayers. Imaging was performed at 50 micrometer resolution in linear mode, and data were processed with IonView software.

Instrumentation Used

• Shimadzu MALDI-8020 benchtop linear TOF mass spectrometer
• Shimadzu MALDI-7090 TOF-TOF mass spectrometer
• SunCollect sprayer (SunChrom)
• IMLayer AERO spraying device (Shimadzu)
• IonView data analysis software

Main Results and Discussion

Lipid imaging of rat brain yielded high-quality pseudo-color distributions correlating to anatomical structures. On-tissue digestion produced characteristic peptides from myelin basic protein localized to white matter and distinct signals in grey matter. Intact protein analysis detected neurogranin (m/z 7537), ubiquitin (m/z 8565), myelin basic protein (m/z 14124), and brain acid soluble protein I (m/z 22104), with spatial patterns matching tissue architecture. Despite the absence of MS/MS, peptide assignments based on accurate mass were consistent with in silico digests.

Benefits and Practical Applications

The compact and cost-effective MALDI-8020 system enables in situ peptide and protein imaging without the need for high-end instrumentation. Its robustness and user-friendly workflow make it suitable for teaching laboratories, small research facilities, and routine QA/QC environments.

Future Trends and Potential Applications

Advancements may include integration of tandem MS capabilities, enhanced mass resolution, automated sample preparation, and miniaturized platforms. Expanded applications could encompass clinical diagnostics, pharmacokinetics, biomarker discovery, and high-throughput tissue screening.

Conclusion

The study demonstrates that a low-cost benchtop MALDI-TOF instrument can effectively image peptides and proteins up to 22 kDa in tissue sections. The method offers a practical alternative for laboratories seeking accessible spatial proteomic analysis.

References

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