Laser ablation electrospray ionization for ambient analysis and molecular imaging with mass spectrometry
Open AccessMass spectrometry (MS) in conjunction with atmospheric-pressure ionization methods offers the ability to study biological systems in their native condition. Currently available ambient ionization sources seek to facilitate in vivo studies by minimizing or eliminating chemical/physical treatment of samples. The present work reports on the development of an atmospheric-pressure ion source, laser ablation electrospray ionization (LAESI) for the direct analysis of biological samples with sufficient water content. A focused laser mid-infrared beam of 2940 nm wavelength was used to excite the OH vibrations in the native water content of samples. As rapid micro-scale ablation set in, biomolecules were catapulted that were converted into gas-phase ions by an electrospray source.LAESI MS is a novel technique to probe the molecular makeup of solutions and tissue samples without the addition of chemical agents, while the specimen is located in the ambient environment. This technique was capable of detecting a variety of molecular classes and size ranges with low limits of detection, and quantitation capabilities over several orders of magnitude.Scanning electron microscopy of the sampling areas on leaf tissues indicated the feasibility of both lateral imaging and depth profiling. By rastering the sample surface with the focused mid-infrared laser beam, LAESI MS opened a way to molecular tissue imaging under native conditions. Lateral imaging helped to uncover tissue-specific distribution for primary and secondary metabolites in plant samples. In rat brain sections, simultaneous imaging of small metabolites and lipids revealed biologically meaningful correlations between these two classes of biomolecules.Molecular depth profiling in combination with lateral imaging enabled us to follow endogenous metabolites in three dimensions in leaf samples. Cross-correlation analysis and colocalization maps were adopted to find synchronous variations in ion intensities to aid the identification of metabolites with distributions that were indicative of their respective biochemical roles in plant defense and photosynthesis. In our feasibility experiments, LAESI imaging MS emerges as a promising approach for the panoramic investigation of biochemical processes in plants and animal tissues under ambient conditions. Diverse fields in the life sciences, especially biochemistry, pharmacology, pathology, and chemical ecology might immediately benefit from this new ionization method.
- All rights reserved
Notice to Authors
If you are the author of this work and you have any questions about the information on this page, please use the Contact form to get in touch with us.