Time of flight secondary ion mass spectrometric (ToF-SIMS) imaging is a powerful bioanalytical tool with the ability to produce molecular images of samples with submicron spatial resolution without the use of labels. In this thesis I will present the development of ToF-SIMS imaging methodology for biological analyses as well as applications that have yielded information about the role of lipids in membrane organization. In the first chapter, I introduce the plasma membrane and describe its fundamental role in maintaining life through the dynamic remodeling of its structure. I focus on two concepts that are believed to influence the localized chemical make up and structure of the membrane, intrinsic curvature and lipid domains. ToF-SIMS imaging is briefly described and a discussion of cluster ion bombardment and sample preparation is included. The chapter concludes with a survey of several important biological studies that have come out of the SIMS community. In Chapter 2 I report a protocol for the use of SIMS imaging to comparatively quantify the relative difference in cholesterol level between the plasma membranes of two cells. This development enables direct comparison of the chemical effects of different drug treatments and incubation conditions in the plasma membrane at the single-cell level. Relative, quantitative ToF-SIMS imaging was used to compare macrophage cells treated to contain elevated levels of cholesterol with respect to control cells. In-situ fluorescence microscopy with two different membrane dyes was used to discriminate morphologically similar but differentially treated cells prior to SIMS analysis. SIMS images of fluorescently identified cells reveal that the two populations of cells have distinct outer leaflet membrane compositions with the membranes of the cholesterol-treated macrophages containing more than twice the amount of cholesterol of control macrophages. Relative quantification with SIMS to compare the chemical composition of single-cells can provide valuable information about normal biological functions, causative agents of diseases, and possible therapies for diseases. Chapter 3 investigates prospects for three-dimensional SIMS analysis of biological materials using model multilayer structures and single cells. The samples were analyzed in a ToF-SIMS spectrometer equipped with a 20 and a 40 keV buckminsterfullerene (C60+) ion source. Specifically, molecular depth profile studies involving dehydrated dipalmitoylphosphatidylcholine (DPPC) organic films indicate that cell membrane lipid materials do not experience significant chemical damage when bombarded with C60+ ion fluences greater than 1015 ions/cm2. Moreover, depth profile analyses of DPPC?sucrose frozen multilayer structures suggest that biomolecule information can be uncovered after the C60+ sputter removal of a 20 nm overlayer with no appreciable loss of underlying molecular signal. The resulting depth information was used to characterize C60+ bombardment of biological materials. This information was used to controllably remove the plasma membrane of a single macrophage cell using a molecular depth profile approach allowing the analysis of the chemistry of the cytoplasm. Two methods that were developed to increase the reproducibility of biological SIMS analysis are covered in Chapter 4. First I demonstrate the utility of the C60+ cluster ion projectile for sputter cleaning biological surfaces to reveal obscured spatio-chemical information. Following the removal of nanometers of material from the surface using sputter cleaning; a frozen-patterned cholesterol film and a freeze-dried tissue sample were analyzed using ToF-SIMS imaging. In both experiments the chemical information was maintained after the sputter dose, due to the minimal chemical damage caused by C60+ bombardment. In fact, the damage to the surface produced by freeze-drying the tissue sample was found to have a greater effect on the loss of cholesterol signal than the sputter-induced damage. In addition to maintaining the chemical information, sputtering did not alter the spatial distribution of the surface chemistry. This approach removes artifacts that are common to many biological sample preparation schemes for ToF-SIMS imaging. Removing these artifacts, which may obscure the surface chemistry of the sample, will increase the number of analyzable samples for SIMS imaging. The second method covered in Chapter 4 is freeze-etching, the practice of removing excess surface water from a sample through sublimation into the vacuum of the analysis environment. This method was used to cryogenically preserve single cells for ToF-SIMS imaging analysis. By removing the excess water, which condenses onto the sample in vacuo, a uniform surface is produced that is ideal for imaging by static SIMS. I demonstrate that the conditions employed to remove deposited water do not adversely affect cell morphology and do not redistribute molecules in the top most surface layers. In addition, I found water could be controllably re-deposited onto the sample at temperatures below -100 oC in vacuum. The re-deposited water increases the ionization of characteristic fragments of biologically interesting molecules 2-fold without loss of spatial resolution. The utilization of freeze-etch methodology will increase the reliability of cryogenic sample preparations for SIMS analysis by providing greater control of the surface environment. Using these procedures we have obtained high quality images and spectra with both atomic bombardment as well as C60+ cluster ion bombardment. Sample handling is also the topic of Chapter 5. It this chapter, I describe a device which has been designed to prepare frozen, hydrated single cell cultures with a freeze fracture methodology for ToF-SIMS analysis in an ION-TOF (GmbH) TOF-SIMS IV mass spectrometer. The device reproducibly produces frozen hydrated sample surfaces for SIMS analysis. I show that SIMS analysis with the Bi32+ produces high-resolution molecular images of single PC12 cells in an ice matrix. I also show that the combination of ionization enhancements that are provided by both the ice matrix and the cluster ion source facilitates the localization of lipid ions that have not been localized in these cells previously. Namely, two fragments of phosphatidlyethanolamine (m/z 124 and m/z 142) and a large fragment of phosphatidylcholine (m/z 224). The ability to localize and measure these ions will increase the number of question that SIMS imaging can be used to answer. In Chapter 6 ToF-SIMS imaging was used to demonstrate that lipid domain formation in mating single-cell organisms is driven by changes in membrane structure. Studies of lipid bilayers in both living and model systems have revealed that lipid composition is coupled to localized membrane structure. However, it is still not clear if the lipids that compose the membrane actively modify membrane structure or if it is structural changes that cause lipid heterogeneity. I report that time of flight secondary ion mass spectrometry images of mating Tetrahymena thermophila acquired before, during and after mating demonstrate that lipid domain formation, identified as a decrease in the lamellar lipid phosphatidylcholine, does not precede structural changes in the membrane. Rather, domains are formed in response to function during cell-to-cell conjugation. ToF-SIMS imaging has been used to collect information with wide implications in all membrane processes. The work presented here is the continuation of a project aimed at chemically characterizing biological samples with spatially resolved mass spectra, with a particular focus on single cell imaging. Much of the work I have done has centered on understanding the capability of current technology and using this understanding to solve a particular problem. This work is vital to keeping SIMS in the biological realm but the development of new technology is the ultimate future for these experiments by increasing the number of tools that the experimenter has to choose from. In Chapter 7 discuss two ongoing projects that I think will lead to the next break through bringing us closer to realizing the goal of this project: a complete chemical map of a single cell.

Mass spectrometry is the measurement of the mass over charge ratio of ions. It is broadly applicable and capable of analyzing complex mixtures. Imaging mass spectrometry (IMS) is a branch of mass spectrometry that analyses ions across a surface while conserving their spatial organization on said surface. At this juncture, the most studied IMS samples are thin tissue sections from plants and animals. Among the molecules routinely imaged by IMS, lipids have generated significant interest. Lipids are important in disease and normal cell function as they form cell membranes and act as signaling molecules for cellular events among many other roles. Considering the potential of lipids in biological and clinical applications and the capability of MALDI to ionize lipids, we developed analytical strategies for the handling of samples and analysis of large lipid MALDI IMS datasets. Lipid degradation is massively important in the food industry with oxidized products producing a bad smell and taste. Similarly, lipids in thin tissue sections cut from whole tissues are subject to degradation, and their degradation products can introduce IMS artifacts and the loss of normally occurring species to degradation can skew accuracy in IMS measures of abundance. Oxidized lipids are also known to be important mediators in the progression of several diseases and their accurate preservation is critical. As IMS studies become multi-institutional and collaborations lead to sample exchange, the need for validated protocols and measures of degradation are necessary. We observed the products of lipid degradation in tissue sections from multiple mouse organs and reported on the conditions promoting and inhibiting their presence as well as the timeline of degradation. Our key findings were the increase in oxidized phospholipids and lysophospholipids from degradation at ambient conditions, the decrease in the presence of lipids containing unsaturations on their fatty acyl chains, and the inhibition of degradation by matrix coating and cold storage of sections under N2 atmosphere. At ambient atmospheric and temperature, lipids degraded into oxidized phospholipids on the time-scale of a normal IMS experiment sample preparation (within 30 min). Lipids then degraded into lysophospholipids' on a time scale on the order of several days. Validation of sample handling is especially important when a greater number of samples are to be analyzed either through a cohort of samples, or analysis of multiple sections from a single tissue as in serial 3D IMS. Atherosclerosis is disease caused by accumulation of cellular material at the arterial wall. The accumulation implanted in the cell wall grows and eventually occludes the blood vessel, or causes a stroke. Atherosclerosis is a 3D phenomenon and serial 3D IMS is useful for its ability to localize molecules throughout the length of a plaque and help to define the molecular mechanisms of plaque development and rupture. Serial 3D IMS has many challenges, many of which are simply a matter of producing 3D reconstructions and interpreting them in a timely fashion. In this aim and using analysis of lipids from atherosclerotic plaques from a human carotid and mouse aortic sinuses, we described 3D reconstruction methods using open-source software. Our methodology provides means to obtain high quality visualizations and demonstrates strategies for rapid interpretation of 3D IMS datasets through multivariate segmentation. Mouse aorta from model animals provided a springboard for developing the methods on lower risk samples with less variation with interesting molecular results. 3D MALDI IMS showed localized phospholipid accumulation in the mouse aortic sinuses with correlation between separate positive and negative ionization datasets. Silver-assisted LDI imaging presented differential localization of free fatty acids, cholesterol / cholesterol esters, and triglycerides. The human carotid's 3D segmentation shows molecular histologies (spatial groupings of imaging pixels with similar spectral fingerprints) correlating to the degree of arterial stenosis. Our results outline the potential for 3D IMS in atherosclerotic research. Molecular histologies and their 3D spatial organization, obtained from the IMS techniques used herein, may predict high-risk features, and particularly identify areas of plaque that have higher-risk of rupture. These investigations would help further unravel the biological complexities of atherosclerosis, and predict clinical outcomes. Colorectal cancer liver metastasis (CRCLM) is the metastatic disease of primary colorectal cancer, one of the most common cancers worldwide. CRC is a cancer of the endothelial lining of the colon or rectum. CRC itself is often cured with surgery, while CRCLM is more deadly and treated with chemotherapy with more limited efficacy. Prognosticating and assessment of tumors is performed using classical histopathology with a margin of error. We have used lipid IMS to identify the histological compartments and extract their signatures. Using these IMS signatures we obtained a quantitative and objective histopathological score that correlates with prognosis. Additionally, by dissecting out the lipid signatures we have identified single lipid moieties that are unique to different histologies that could potentially be used as new biomarkers for assessing response to therapy. Particularly, we found a series of plasmalogen and sphingolipid species that differentiate infarct-like and usual necrosis, typical of chemotherapeutic response and normal tumor function, respectively.

Covers the area of lipidomics from fundamentals and theory to applications Presents a balanced discussion of the fundamentals, theory, experimental methods and applications of lipidomics Covers different characterizations of lipids including Glycerophospholipids; Sphingolipids; Glycerolipids and Glycolipids; and Fatty Acids and Modified Fatty Acids Includes a section on quantification of Lipids in Lipidomics such as sample preparation; factors affecting accurate quantification; and data processing and interpretation Details applications of Lipidomics Tools including for Health and Disease; Plant Lipidomics; and Lipidomics on Cellular Membranes

This second edition details new and updated chapters on key methodologies and breakthroughs in the mass spectrometry imaging (MSI) field. Chapters guide readers through nano-Desorption Electrospray Ionisation (nDESI), Matrix Assisted Laser Desorption Ionisation-2 (MALDI-2), Laser Ablation - Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) ,Imaging Mass Cytometry (IMC) with a variety of diverse samples including eye tissue, crop analysis, 3D cell culture models, and counterfeit goods analysis. Written in the format of the highly successful Methods in Molecular Biology series, each chapter includes an introduction to the topic, lists necessary materials and reagents, includes tips on troubleshooting and known pitfalls, and step-by-step, readily reproducible protocols. Authoritative and cutting-edge, Imaging Mass Spectrometry: Methods and Protocols, Second Edition aims to be a useful and practical guide to new researchers and experts looking to expand their knowledge.

Mass Spectrometry for Lipidomics All-in-one guide to successful lipidomic analysis, combining the latest advances and best practices from academia, industry, and clinical research Mass Spectrometry for Lipidomics presents a systematic overview of lipidomic analysis, covering established standards of lipid analysis, available technology, and key lipid classes, as well as applications in basic research, medicine, pharma, and the food industry. Through connecting recent technological advances with key application areas, this unique guide bridges the gap between academia and industry by translating the vast body of knowledge that has been gained in the past decade into much-needed practical advice for novices as well as routine users. Edited by the president and vice-president of the International Lipidomics Society with contributions from the top experts in lipid analysis, Mass Spectrometry for Lipidomics covers a wide range of key topics, including: Aspects of sample preparation, separation methods, different mass spectrometry modes, as well as identification and quantitation, including the use of bioinformatics tools for data analysis Identification, quantitation and profiling of lipids in different types of biological samples Analytical approaches for all major classes of biological lipids, from fatty acids to phospholipids to sterols Novel applications in biological research, clinical diagnostics, as well as food and crop science For analytical chemists, biochemists, clinical chemists, and analytical laboratories and hospitals, Mass Spectrometry for Lipidomics presents a comprehensive and authoritative overview of the subject, with unmatched expertise from practicing professionals actively involved in the latest research.

Addressing the widespread need for a practical guide to imaging mass spectrometry (IMS), this book presents the protocols of IMS technology. As that technology expands, research groups around the world continue its development. Pharmaceutical companies are using IMS for drug analyses to study pharmacokinetics and medical properties of drugs. Drug research and disease-related biomarker screening are experiencing greater use of this technology, with a concurrent increase in the number of researchers in academia and industry interested in wider applications of IMS. Intended for beginners or those with limited experience with IMS technology, this book provides practical details and instructions needed for immediate know-how, including the preparation of animal tissue samples, the application of a matrix, instrumental operations, and data analysis, among others. By describing the foundations of IMS, this volume contributes to the ongoing development of the field and to progress in human health.