Hung Su

Matrix-assisted laser desorption ionization/time-of-flight mass spectrometry for clinical diagnosis

BACKGROUND Matrix-assisted laser desorption ionization/time-of-flight (MALDI-TOF) mass spectrometry is known as an extremely sensitive analytical tool for characterizing different types of biological compounds including proteins, peptides and lipids. Since MALDI-TOF analysis requires very simple sample pretreatment, the technique can be used for rapidly detecting biochemical compounds serving as disease biomarkers. RESULTS This mini-review focuses on the applications of MALDI-TOF in the detection of potential disease biomarkers in various biological samples. CONCLUSIONS The potential disease biomarkers are mostly abundant proteins, peptides, or lipids including: albumin; hemoglobin; α-defensins; trimethylamine; phospholipids; and glycated α- and β-globin, which are indicators of albuminuria; fecal occult blood and ischemic stroke; dry eye disease and/or aging; trimethylaniuria; breast cancer; and diabetes, respectively.

Rapid identification of pesticides in human oral fluid for emergency management by thermal desorption electrospray ionization/mass spectrometry

The World Health Organization acknowledges that pesticide self-poisoning is among the most frequently used methods of suicide worldwide. It is therefore of the highest importance to promptly identify the type of pesticides ingested by self-poisoning patients because different pesticides cause intoxication through different mechanisms, requiring different therapeutic strategies, precautions against contraindicating actions, directions of clinical course monitoring and predictions of prognosis. In this perspective Special Feature, Pr. Bai-Hsiun Chen (Laboratory Medicine and Pediatrics, College of Medicine, Kaohsiung Medical University, Taiwan) and colleagues propose a point-of-care analytical method for rapid identification of five residual pesticides in oral fluid using thermal desorption-electrospray ionization/mass spectrometry (TD-ESI/MS). This non-invasive approach can expedite emergency care and may provide important toxicological information for decision-making during critical resuscitation.

Biomarker Characterization by MALDI–TOF/MS

Mass spectrometric techniques frequently used in clinical diagnosis, such as gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, ambient ionization mass spectrometry, and matrix-assisted laser desorption ionization/time-of-flight mass spectrometry (MALDI-TOF/MS), are discussed. Due to its ability to rapidly detect large biomolecules in trace amounts, MALDI-TOF/MS is an ideal tool for characterizing disease biomarkers in biologic samples. Clinical applications of MS for the identification and characterization of microorganisms, DNA fragments, tissues, and biofluids are introduced. Approaches for using MALDI-TOF/MS to detect various disease biomarkers including peptides, proteins, and lipids in biological fluids are further discussed. Finally, various sample pretreatment methods which improve the detection efficiency of disease biomarkers are introduced.

Rapid identification of pesticides in human oral fluid for emergency management by thermal desorption electrospray ionization/mass spectrometry: Emergent pesticide identification by ambient MS

Self-poisoning with pesticides accounts for approximately one-third of all suicides worldwide. To expedite rescue in the emergency department, it is essential to develop a point-of-care analytical method for rapid identification of ingested pesticides. In this study, five of the most common pesticides ingested by self-poisoning patients in Taiwan were analyzed from oral fluid samples. Pesticide-oral fluid mixtures were applied on a cotton swab and then transferred into methanol. A metallic probe was used to sample the methanol solution for subsequent thermal desorption-electrospray ionization mass spectrometry analysis. Altogether, pesticide sampling, transfer, desorption, ionization, and detection took less than 1 min. The reproducibility of this method (n = 6) was shown in the observed low-relative standard deviation (<7%) in the detection of pesticide in oral fluid. The detection limits of the pesticides in oral fluid obtained from four human subjects by thermal desorption-electrospray ionization mass spectrometry were between 1-10 ppb with relative standard deviation 10.7%. Moreover, in this study, linear responses of five pesticides in oral fluid with concentrations between 1 ppb-1 ppm (R2 between 0.9938 and 0.9988) were observed. As the whole analytical process is extremely short, this technique allows for early non-invasive point-of-care identification of pesticides in the oral fluid of self-poisoning patients in the emergency room, providing important toxicological information for decision-making during critical resuscitation.

Diagnosis of albuminuria by tryptic digestion and matrix-assisted laser desorption ionization/time-of-flight mass spectrometry

BACKGROUND Matrix-assisted laser desorption ionization/time-of-flight (MALDI-TOF) mass spectrometry has been successfully used to detect trace albumin in urine for the diagnosis of albuminuria. However, only the monomeric form of albumin was detected with this approach. METHODS Trypsin was used to digest urinary albumin and its related compounds in urine to produce characteristic peptides. The digest solution was subsequently analyzed by MALDI-TOF MS to obtain peptide ion signals which were used as diagnostic biomarkers for albuminuria. RESULTS The analytical protocol was optimized for efficient digestion and high-performance MALDI-TOF MS analysis. The limit of detection (LOD) of albumin in urine was about 5×10(-7)M. CONCLUSIONS Trypsin digestion combined with MALDI-TOF MS analysis is an efficient and simple approach for rapidly diagnosing albuminuria.

Using thermal desorption electrospray ionization mass spectrometry to rapidly determine antimicrobial preservatives in cosmetics.

RATIONALE Characterization and quantification of permitted preservatives are important inspections to prevent the overuse of preservatives in authentic formulations. However, the complexity of sample matrices makes preservative determination in cosmetics a tedious process. A rapid analytical strategy to identify preservatives would insure large numbers of products are in compliance with government regulations. METHODS Thermal desorption electrospray ionization mass spectrometry (TD-ESI-MS) was used to directly detect preservative compounds in authentic formulations without sample pretreatment. The technique employs a metal probe, which was configured for sampling cosmetics in their original states and was inserted in a closed preheated oven to thermally desorb analytes. The desorbed analytes were then carried by a nitrogen gas stream into an ESI plume, where the formed ions were subsequently detected by the mass analyzer. RESULTS The TD-ESI mass and tandem mass spectra of different classes of preservative standards were rapidly obtained, and the limits of detection were far below the legal limit of their respective concentrations. The preservatives were also directly detected in different types of authentic formulations in the absence of sample preparation, and within a few seconds per sample. Calibration curves for preservatives in four common formulations yielded good linearity in the regulation-allowed range. CONCLUSIONS Due to its sensitivity, short analysis time, repeatability, and quantitative ability, TD-ESI-MS may serve as a suitable tool for large-scale screening of cosmetic preservatives to assure product safety. Copyright

Point-of-care identification of organophosphates in gastric juice by ambient mass spectrometry in emergency settings

BACKGROUND For emergency management, it is important to promptly identify the organophosphate ingested by self-poisoning patients since different organophosphates cause intoxication through different mechanisms and require different therapeutic strategies. This study aimed at the development of a point-of-care ambient mass spectrometric approach for rapid identification of organophosphate(s) in gastric juice for emergency management. METHODS Six organophosphate insecticides that are commonly ingested by self-poisoning patients in Taiwan were examined. The sample solutions were prepared and diluted with human gastric juice. A direct metallic probe was dipped and removed immediately from the sample solution. The probe was then inserted into the thermal desorption-electrospray ionization/mass spectrometry (TD-ESI/MS) to detect the analyte on the probe. RESULTS Since no pretreatment of the specimen was required, the sampling processes followed by thermal desorption-electrospray ionization and mass spectrometric analysis of the organophosphate in the gastric juice were completed within 30 s. The detection limit of the organophosphates is at the 10-100 parts per billion level. Good linearity was observed between the corresponding changes in mass spectrometric signal intensities and the changes of organophosphate concentrations within the range of 5-1000 parts per billion. The high efficiency of this ambient mass spectrometric platform was further confirmed when a real sample of the drained gastric lavage fluid of a patient who suffered from ingestion of chlorpyrifos was collected in the emergency room and tested with this cutting-edge technique. CONCLUSIONS The results suggested that TD-ESI/MS is promising in promptly providing toxicological information to assist succeeding medical management in an emergency room.

Detection of α–defensin in blister fluids as potential biomarkers for bullous pemphigoid patients by matrix-assisted laser desorption ionization/time-of-flight mass spectrometry

BACKGROUND Bullous pemphigoid (BP) is a chronic blistering disease that manifests as multiple tense bullae on the limbs and body. Detecting biomarkers present in skin fluids may assist in the early diagnosis and treatment of BP. In this study, a modern mass spectrometric method was developed for screening biomarkers in blister fluids collected from patients. METHODS Blister fluids collected from BP patients and physically injured patients were analyzed and compared using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). The blister fluids were mixed with MALDI matrix solution on the target plate; after drying, they were analyzed by MALDI-TOF MS. RESULTS Alpha-defensins 1-3 were detected in the samples collected from all BP patients and absent in all patients with physical injuries. Therefore, alpha-defensins 1-3 are potential biomarkers for BP and can be used to differentiate between blisters caused by BP and those caused by physical injuries. Compared to traditional skin biopsy methods that use immunofluorescent stains, analyzing biomarkers in blister fluids using MALDI-TOF is a more rapid and less invasive method. CONCLUSIONS MALDI-TOF-MS is a non-invasive and efficient method that is able to rapidly distinguish between blisters caused by BP and those caused by physical injuries.

High-throughput screening of phthalate-containing objects in the kindergartens by ambient mass spectrometry

High-throughput screening of plastic products in childrens living environment is necessary to identify phthalate-containing objects for the concern of public health and safety. A novel strategy of probe collecting technique combined with ambient mass spectrometry was developed to carry out the large-scale sample analysis. Analytes from the surface of approximately 500 objects each in two kindergartens in Taiwan were collected using the same number of the metallic probes. After being delivered to laboratory, the analytes on the probes were analyzed with thermal desorption-electrospray ionization/mass spectrometry (TD-ESI/MS). As sample pretreatment was unnecessary, the analysis of phthalates on a probe was completed within 30 s enabling high-throughput screening of a large number of objects. All procedure including sampling and TD-ESI/MS analysis together with report writing for a kindergarten was completed in one day. A reasonable relative standard deviation (<15.6%) was obtained from replicate analyses of phthalate standards. Single-point calibration was used to perform semi-quantitative analysis, and results were validated by liquid chromatography/mass spectrometry (LC/MS). It was found that 20-40% of the objects in two kindergartens contained greater than low-level (>2 ng) of phthalates and 40-60% of the objects in the kindergartens contained more than one kind of phthalate.

Fine Needle Aspiration Combined with Matrix-Assisted Laser Desorption Ionization Time-of-Flight/Mass Spectrometry to Characterize Lipid Biomarkers for Diagnosing Accuracy of Breast Cancer

Background Fine needle aspiration (FNA) cytology has been widely used for pathologic assessment of breast lesions. However, the examination suffers a risk of false‐negative results owing to insufficient sample volumes, inaccurate sampling positions, nondefinitive cytologic features, or suboptimal cell preservation. One approach to improve its accuracy is using modern mass spectrometry to detect disease biomarkers, of which the tissue samples are collected through FNA. Methods The biological compounds in the FNA tissue samples were extracted and characterized by matrix‐assisted laser desorption ionization time‐of‐flight/mass spectrometry (MALDI‐TOF/MS). The results were further analyzed by principal component analysis. Distribution of lipid biomarkers on tissues was explored by imaging mass spectrometry. Results Lipid profiles of the tissue samples collected by FNA were rapidly obtained through MALDI‐TOF/MS analysis. Phosphatidylcholines and triacylglycerols were detected as the predominant compounds in cancerous and normal regions, respectively. The samples were clearly classified by principal component analysis, based on the differences in their lipid profiles. Different lipid patterns were clearly viewed through the molecular imaging of normal and tumorous regions of breast tissue samples. Conclusion The FNA‐MALDI‐TOF/MS approach can provide complementary information for pathological examinations and improve the accuracy of breast cancer diagnoses. Owing to the ease of operation and automation, it is possible to efficiently screen the lipid biomarkers in a large number of tissue samples by means of MALDI‐TOF/MS. Micro‐Abstract MALDI‐TOF/MS is sensitive to detect lipid ion signals in fine needle aspiration sample, thus allowing normal and tumorous tissues to be effectively distinguished by principal component analysis. FNA combined with MALDI‐TOF/MS approach provides complementary information of cytology, and can be useful in improving the accuracy of breast cancer diagnoses. The results of MALDI imaging mass spectrometry also confirmed the results obtained by FNA‐MALDI‐TOF/MS.