BS, State University of Campinas, Sao Paulo, Brazil, Chemistry (2007)
Doctor of Philosophy, Purdue University (2012)
Dick Zare, Postdoctoral Faculty Sponsor
Mass spectrometry imaging under ambient conditions
MASS SPECTROMETRY REVIEWS
2013; 32 (3): 218-243
Mass spectrometry imaging (MSI) has emerged as an important tool in the last decade and it is beginning to show potential to provide new information in many fields owing to its unique ability to acquire molecularly specific images and to provide multiplexed information, without the need for labeling or staining. In MSI, the chemical identity of molecules present on a surface is investigated as a function of spatial distribution. In addition to now standard methods involving MSI in vacuum, recently developed ambient ionization techniques allow MSI to be performed under atmospheric pressure on untreated samples outside the mass spectrometer. Here we review recent developments and applications of MSI emphasizing the ambient ionization techniques of desorption electrospray ionization (DESI), laser ablation electrospray ionization (LAESI), probe electrospray ionization (PESI), desorption atmospheric pressure photoionization (DAPPI), femtosecond laser desorption ionization (fs-LDI), laser electrospray mass spectrometry (LEMS), infrared laser ablation metastable-induced chemical ionization (IR-LAMICI), liquid microjunction surface sampling probe mass spectrometry (LMJ-SSP MS), nanospray desorption electrospray ionization (nano-DESI), and plasma sources such as the low temperature plasma (LTP) probe and laser ablation coupled to flowing atmospheric-pressure afterglow (LA-FAPA). Included are discussions of some of the features of ambient MSI for example the ability to implement chemical reactions with the goal of providing high abundance ions characteristic of specific compounds of interest and the use of tandem mass spectrometry to either map the distribution of targeted molecules with high specificity or to provide additional MS information on the structural identification of compounds. We also describe the role of bioinformatics in acquiring and interpreting the chemical and spatial information obtained through MSI, especially in biological applications for tissue diagnostic purposes. Finally, we discuss the challenges in ambient MSI and include perspectives on the future of the field.
View details for DOI 10.1002/mas.21360
View details for Web of Science ID 000318032000003
View details for PubMedID 22996621
Ambient mass spectrometry for the intraoperative molecular diagnosis of human brain tumors
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2013; 110 (5): 1611-1616
The main goal of brain tumor surgery is to maximize tumor resection while preserving brain function. However, existing imaging and surgical techniques do not offer the molecular information needed to delineate tumor boundaries. We have developed a system to rapidly analyze and classify brain tumors based on lipid information acquired by desorption electrospray ionization mass spectrometry (DESI-MS). In this study, a classifier was built to discriminate gliomas and meningiomas based on 36 glioma and 19 meningioma samples. The classifier was tested and results were validated for intraoperative use by analyzing and diagnosing tissue sections from 32 surgical specimens obtained from five research subjects who underwent brain tumor resection. The samples analyzed included oligodendroglioma, astrocytoma, and meningioma tumors of different histological grades and tumor cell concentrations. The molecular diagnosis derived from mass-spectrometry imaging corresponded to histopathology diagnosis with very few exceptions. Our work demonstrates that DESI-MS technology has the potential to identify the histology type of brain tumors. It provides information on glioma grade and, most importantly, may help define tumor margins by measuring the tumor cell concentration in a specimen. Results for stereotactically registered samples were correlated to preoperative MRI through neuronavigation, and visualized over segmented 3D MRI tumor volume reconstruction. Our findings demonstrate the potential of ambient mass spectrometry to guide brain tumor surgery by providing rapid diagnosis, and tumor margin assessment in near-real time.
View details for DOI 10.1073/pnas.1215687110
View details for Web of Science ID 000314558100016
View details for PubMedID 23300285
Chemical Aspects of the Extractive Methods of Ambient Ionization Mass Spectrometry
ANNUAL REVIEW OF PHYSICAL CHEMISTRY, VOL 64
2013; 64: 481-505
Ambient ionization techniques allow complex chemical samples to be analyzed in their native state with minimal sample preparation. This brings the obvious advantages of simplicity, speed, and versatility to mass spectrometry: Desorption electrospray ionization (DESI), for example, is used in chemical imaging for tumor margin diagnosis. This review on the extractive methods of ambient ionization focuses on chemical aspects, mechanistic considerations, and the accelerated chemical reactions occurring in charged liquid droplets generated in the spray process. DESI uses high-velocity solvent droplets to extract analytes from surfaces. Nano-DESI employs liquid microjunctions for analyte dissolution, whereas paper-spray ionization uses DC potentials applied to wet porous material such as paper or biological tissue to field emit charged analyte-containing solvent droplets. These methods also operate in a reactive mode in which added reagents allow derivatization during ionization. The accelerated reaction rates seen in charged microdroplets are useful in small-scale rapid chemical synthesis.
View details for DOI 10.1146/annurev-physchem-040412-110026
View details for Web of Science ID 000321771600022
View details for PubMedID 23331308
Classifying Human Brain Tumors by Lipid Imaging with Mass Spectrometry
2012; 72 (3): 645-654
Brain tissue biopsies are required to histologically diagnose brain tumors, but current approaches are limited by tissue characterization at the time of surgery. Emerging technologies such as mass spectrometry imaging can enable a rapid direct analysis of cancerous tissue based on molecular composition. Here, we illustrate how gliomas can be rapidly classified by desorption electrospray ionization-mass spectrometry (DESI-MS) imaging, multivariate statistical analysis, and machine learning. DESI-MS imaging was carried out on 36 human glioma samples, including oligodendroglioma, astrocytoma, and oligoastrocytoma, all of different histologic grades and varied tumor cell concentration. Gray and white matter from glial tumors were readily discriminated and detailed diagnostic information could be provided. Classifiers for subtype, grade, and concentration features generated with lipidomic data showed high recognition capability with more than 97% cross-validation. Specimen classification in an independent validation set agreed with expert histopathology diagnosis for 79% of tested features. Together, our findings offer proof of concept that intraoperative examination and classification of brain tissue by mass spectrometry can provide surgeons, pathologists, and oncologists with critical and previously unavailable information to rapidly guide surgical resections that can improve management of patients with malignant brain tumors.
View details for DOI 10.1158/0008-5472.CAN-11-2465
View details for Web of Science ID 000300405900009
View details for PubMedID 22139378
Desorption Electrospray Ionization then MALDI Mass Spectrometry Imaging of Lipid and Protein Distributions in Single Tissue Sections
2011; 83 (22): 8366-8371
Imaging mass spectrometry (MS) is a powerful technique for mapping the spatial distributions of a wide range of chemical compounds simultaneously from a tissue section. Co-localization of the distribution of individual molecular species, including particular lipids and proteins, and correlation with the morphological features of a single tissue section are highly desirable for comprehensive tissue analysis and disease diagnosis. We now report on the use, in turn, of desorption electrospray ionization (DESI), matrix assisted laser desorption ionization (MALDI), and then optical microscopy to image lipid and protein distributions in a single tissue section. This is possible through the use of histologically compatible DESI solvent systems, which allow for sequential analyses of the same section by DESI then MALDI. Hematoxylin and eosin (H&E) staining was performed on the same section after removal of the MALDI matrix. This workflow allowed chemical information to be unambiguously matched to histological features in mouse brain tissue sections. The lipid sulfatide (24:1), detected at m/z 888.8 by DESI imaging, was colocalized with the protein MBP isoform 8, detected at m/z 14117 by MALDI imaging, in regions corresponding to the corpus callosum substructure of the mouse brain, as confirmed in the H&E images. Correlation of lipid and protein distributions with histopathological features was also achieved for human brain cancer samples. Higher tumor cell density was observed in regions demonstrating higher relative abundances of oleic acid, detected by DESI imaging at m/z 281.4, and the protein calcyclin, detected by MALDI at m/z 10085, for a human glioma sample. Since correlation between molecular signatures and disease state can be achieved, we expect that this methodology will significantly enhance the value of MS imaging in molecular pathology for diagnosis.
View details for DOI 10.1021/ac202016x
View details for Web of Science ID 000296830200002
View details for PubMedID 21975048
Desorption electrospray ionization mass spectrometry for lipid characterization and biological tissue imaging
BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR AND CELL BIOLOGY OF LIPIDS
2011; 1811 (11): 946-960
Desorption electrospray ionization mass spectrometry (DESI-MS) imaging of biological samples allows untargeted analysis and structural characterization of lipids ionized from the near-surface region of a sample under ambient conditions. DESI is a powerful and sensitive MS ionization method for 2D and 3D imaging of lipids from direct and unmodified complex biological samples. This review describes the strengths and limitations of DESI-MS for lipid characterization and imaging together with the technical workflow and a survey of applications. Included are discussions of lipid mapping and biomarker discovery as well as a perspective on the future of DESI imaging.
View details for DOI 10.1016/j.bbalip.2011.05.006
View details for Web of Science ID 000297399000029
View details for PubMedID 21645635
- Nondestructive, Histologically Compatible Tissue Imaging by Desorption Electrospray Ionization Mass Spectrometry CHEMBIOCHEM 2011; 12 (14): 2129-2132
Perspectives in imaging using mass spectrometry
2011; 47 (10): 2741-2746
Imaging mass spectrometry (MS) allows a remarkable range of measurements including diagnosis of disease state of tissue based on detailed information on its chemical constituents, especially lipids and proteins. The recent emergence of ambient ionization allows imaging in the open environment without sample preparation. In this review, we briefly describe the history of imaging MS highlighting its main techniques and applications. We also demonstrate how the detailed molecular information obtained by imaging MS makes this technique suitable for a range of forensic and clinical applications with the potential to be successfully developed all the way to intra-surgical practice.
View details for DOI 10.1039/c0cc03518a
View details for Web of Science ID 000287530700001
View details for PubMedID 21161110
Multivariate statistical differentiation of renal cell carcinomas based on lipidomic analysis by ambient ionization imaging mass spectrometry
ANALYTICAL AND BIOANALYTICAL CHEMISTRY
2010; 398 (7-8): 2969-2978
Desorption electrospray ionization (DESI) mass spectrometry (MS) was used in an imaging mode to interrogate the lipid profiles of thin tissue sections of 11 sample pairs of human papillary renal cell carcinoma (RCC) and adjacent normal tissue and nine sample pairs of clear cell RCC and adjacent normal tissue. DESI-MS images showing the spatial distributions of particular glycerophospholipids (GPs) and free fatty acids in the negative ion mode were compared to serial tissue sections stained with hematoxylin and eosin (H&E). Increased absolute intensities as well as changes in relative abundance were seen for particular compounds in the tumor regions of the samples. Multivariate statistical analysis using orthogonal projection to latent structures treated partial least square discriminate analysis (PLS-DA) was used for visualization and classification of the tissue pairs using the full mass spectra as predictors. PLS-DA successfully distinguished tumor from normal tissue for both papillary and clear cell RCC with misclassification rates obtained from the validation set of 14.3% and 7.8%, respectively. It was also used to distinguish papillary and clear cell RCC from each other and from the combined normal tissues with a reasonable misclassification rate of 23%, as determined from the validation set. Overall DESI-MS imaging combined with multivariate statistical analysis shows promise as a molecular pathology technique for diagnosing cancerous and normal tissue on the basis of GP profiles.
View details for DOI 10.1007/s00216-010-4259-6
View details for Web of Science ID 000284542300023
View details for PubMedID 20953777
Cholesterol Sulfate Imaging in Human Prostate Cancer Tissue by Desorption Electrospray Ionization Mass Spectrometry
2010; 82 (9): 3430-3434
Development of methods for rapid distinction between cancerous and non-neoplastic tissues is an important goal in disease diagnosis. To this end, desorption electrospray ionization mass spectrometry (DESI-MS) imaging was applied to analyze the lipid profiles of thin tissue sections of 68 samples of human prostate cancer and normal tissue. The disease state of the tissue sections was determined by independent histopathological examination. Cholesterol sulfate was identified as a differentiating compound, found almost exclusively in cancerous tissues including tissue containing precancerous lesions. The presence of cholesterol sulfate in prostate tissues might serve as a tool for prostate cancer diagnosis although confirmation through larger and more diverse cohorts and correlations with clinical outcome data is needed.
View details for DOI 10.1021/ac9029482
View details for Web of Science ID 000277213400009
View details for PubMedID 20373810
- Discrimination of Human Astrocytoma Subtypes by Lipid Analysis Using Desorption Electrospray Ionization Imaging Mass Spectrometry ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 2010; 49 (34): 5953-5956
- Three-Dimensional Vizualization of Mouse Brain by Lipid Analysis Using Ambient Ionization Mass Spectrometry ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 2010; 49 (5): 873-876
Analysis of biodiesel and biodiesel-petrodiesel blends by high performance thin layer chromatography combined with easy ambient sonic-spray ionization mass spectrometry
2009; 134 (8): 1652-1657
High performance thin layer chromatography (HPTLC) combined with on-spot detection and characterization via easy ambient sonic-spray ionization mass spectrometry (EASI-MS) is applied to the analysis of biodiesel (B100) and biodiesel-petrodiesel blends (BX). HPTLC provides chromatographic resolution of major components whereas EASI-MS allows on-spot characterization performed directly on the HPTLC surface at ambient conditions. Constituents (M) are detected by EASI-MS in a one component-one ion fashion as either [M + Na](+) or [M + H](+). For both B100 and BX samples, typical profiles of fatty acid methyl esters (FAME) detected as [FAME + Na](+) ions allow biodiesel typification. The spectrum of the petrodiesel spot displays a homologous series of protonated alkyl pyridines which are characteristic for petrofuels (natural markers). The spectrum for residual or admixture oil spots is characterized by sodiated triglycerides [TAG + Na](+). The application of HPTLC to analyze B100 and BX samples and its combination with EASI-MS for on-spot characterization and quality control is demonstrated.
View details for DOI 10.1039/b817847j
View details for Web of Science ID 000268131500021
View details for PubMedID 20448934
Atmospheric Pressure Thermal Dissociation of Phospho- and Sulfopeptides
JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY
2008; 19 (12): 1897-1905
Several phospho- and sulfopeptides were subjected to atmospheric pressure thermal dissociation (APTD), which was effected by passing peptide ions generated by electrosonic spray ionization (ESSI) through a heated coiled metal tube. Sequence informative fragment ions including a-, b-, c-, and y-types of ions were observed with increased relative intensities under APTD compared with collision-induced dissociation (CID), performed inside the ion trap. A certain degree of preservation of phosphate and sulfate ester moieties was observed for some fragments ions under APTD. The neutral fragments generated outside the mass spectrometer were further analyzed via on-line corona discharge to provide rich and complementary sequence information to that provided by the fragment ions directly obtained from APTD, although complete losses of the modification groups were noted. Improved primary sequence information for phospho- and sulfopeptides was typically obtained by analyzing both ionic and neutral fragments from APTD compared with fragment ions from CID alone. Localization of the modification sites of phospho- and sulfopeptides was achieved by combining the structural information acquired from APTD and CID.
View details for DOI 10.1016/j.jasms.2008.07.019
View details for Web of Science ID 000261808900022
View details for PubMedID 18722138
- Organic reactions of ionic intermediates promoted by atmospheric-pressure thermal activation ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 2008; 47 (18): 3422-3425
Neutral fragment mass spectra via ambient thermal dissociation of peptide and protein ions
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2007; 129 (18): 5880-5886
A novel method for the fragmentation of peptide and protein ions at atmospheric pressure outside the mass spectrometer is described. Peptide/protein ions generated by electrosonic spray ionization (ESSI) are carried through a heated coiled metal tube where they fragment. Fragment ions of types a, b, and y are observed for peptides such as angiotensin II and bradykinin. In the case of phosphopeptides, informative b and y ions which preserve the labile phosphate groups are observed in the negative ion mode, which is potentially useful in the location of phosphorylation sites in proteins through chemical analysis of phosphopeptides. The thermal dissociation method extends to proteins such as ubiquitin and myoglobin, giving rise to y-type and other fragment ions. The most important feature of this method is that it also allows characterization of the neutral fragments arising from thermal dissociation by use of on-line corona discharge ionization. This neutral re-ionization experiment is much easier to perform outside the mass spectrometer than as conventionally done, in vacuum. It yields increased structural information from the resulting mass spectra in both the positive and the negative ion modes.
View details for DOI 10.1021/ja067712v
View details for Web of Science ID 000246180200034
View details for PubMedID 17432855