Nanoparticle-assisted laser desorption/ionization mass spectrometry: novel sample preparation methods and nanoparticle screening for plant metabolite imaging

Yagnik, Gargey
Major Professor
Young-Jin Lee
Committee Member
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The main goal of the presented research is development of nanoparticle based matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS). This dissertation includes the application of previously developed data acquisition methods, development of novel sample preparation methods, application and comparison of novel nanoparticle matrices, and comparison of two nanoparticle matrix application methods for MALDI-MS and MALDI-MS imaging. Chapter 1 presents background information about MALDI-MS and a general workflow for MALDI-MS imaging experiments. Chapter 6 provides a summary of the presented work and possible future directions.

Chapter 2 describes a “multiplex” MALDI-MS imaging technique applied to study latent human fingerprints. In this study, we applied previously developed multiplex data acquisition techniques for the detection of endogenous and exogenous compounds with structural information in a single MALDI-MS imaging experiment. This study also depicts the importance of the sublimation matrix application method for analysis of very delicate samples such as latent fingerprints.

Chapter 3 presents the development of novel sample preparation methods for nanoparticle-assisted laser desorption/ionization-mass spectrometry -mass spectrometry (NALDI-MS) imaging of metabolites in plant tissues. In this chapter, we developed a novel fracturing method for MALDI-MS/ NALDI-MS imaging of rice leaf to study a plant-pathogen interactions. We successfully detected and imaged diterpenoids produced against the Xanthomonas oryzae pv. oryzae infection in rice leaves.

Chapter 4 is focused on novel nanoparticle (NP) matrix development for NALDI-MS of low-molecular weight plant metabolites. This large-scale NP screening was inspired by the success of the metabolite detection/imaging in Chapter 3. In this work, we studied three different classes of NPs for desorption/ionization of a wide variety of plant metabolites and sought to shed some light on the NALDI mechanism.

Chapter 5 is a further extension of the study in Chapter 4, in which we compare two NP application methods for efficiency of desorption/ionization of plant metabolites and homogeneity of application. We compare application of a nanoparticle suspension by oscillating capillary nebulizer and solvent-free sputter coating of metal NPs. The work presented in Chapters 4 and 5 will be helpful for development of novel matrices for analysis and imaging of low-molecular weight metabolites that are difficult to ionize using traditional MALDI-MS matrices.