TIMS enabled quantification of small molecules in MALDI Imaging

Importance of the Topic

Quantitative MALDI imaging mass spectrometry remains hindered by isobaric interference matrix background and ion suppression yet precise spatial quantification of drugs and metabolites in tissue is essential for pharmacology drug development and therapeutic monitoring

Study Objectives and Overview

This work demonstrates how the timsTOF fleX platform enables reliable quantitative MALDI imaging of small molecule drugs Four BRAF inhibitor compounds were spiked into mouse brain homogenate to create a tissue mimetic ranging from 1 to 100 micromolar A co dosing experiment explored simultaneous detection of topotecan and gadavist across a broad mass range

Methodology

• Sample Preparation Mouse brain homogenate was spiked with serial dilutions of target drugs in DMSO embedded in gelatin microarray molds cryosectioned at 10 µm and thaw mounted on ITO coated slides
• Matrix Application A matrix solution of 2 5 dihydroxybenzoic acid in 70 30 methanol 0 1 percent TFA with 1 percent DMSO was applied using a TM sprayer with controlled flow rate nozzle velocity temperature and nitrogen pressure then recrystallized at 85 °C
• Data Acquisition MALDI imaging was performed on timsTOF fleX in positive ion mode with ion mobility separation PASEF and quadrupole isolation Pixel size was 50 µm2 with 100 laser shots per pixel Direct infusion ESI defined optimal ion transfer funnel quadrupole collision cell and focus voltages
• Data Analysis Visualization and quantitation were achieved using SCiLS Lab and TIMS Viewer

Used Instrumentation

• timsTOF fleX mass spectrometer
• Electrospray ionization source for method calibration
• TM sprayer for uniform matrix deposition

Main Results and Discussion

• Isobaric Separation TIMS resolved near isobaric species such as monomethyl auristatin E and a tissue related peak at m/z 7185 enhancing specificity in the mass spectrum
• Sensitivity Enhancement The combination of TIMS PASEF and selective quadrupole elution lowered detection limits to approximately 1 micromolar for encorafenib and trametinib
• Charge State Resolution TIMS distinguished gadavist monomer and dimer ion series preventing signal overlap and preserving linear calibration dynamic range
• Co dosing Performance Fine tuning of ion optics achieved balanced sensitivity for topotecan and gadavist across a wide mass window

Benefits and Practical Applications

• High specificity and sensitivity for targeted compounds without chromatographic separation
• Accurate calibration curves via mobility filtering reduce chemical background interference
• Applicable to pharmacokinetic pharmacodynamic and drug distribution studies in tissue sections

Future Trends and Opportunities

Integration of high throughput TIMS PASEF workflows expanded multiplexed drug panels multimodal imaging combinations and application in clinical precision medicine are promising directions

Conclusion

timsTOF fleX overcomes key challenges in quantitative MALDI imaging by leveraging ion mobility separation PASEF and targeted quadrupole isolation delivering reliable sensitive spatial quantification of small molecule therapeutics in tissue

Reference

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