Nanoengineered micro gold shells for LDI-TOF analysis of small molecules
ABSTRACT This paper reports on analyses of small molecules with laser desorption/ionization time of flight (LDI-TOF) mass spectrometry (MS) using nanostructure-embedded micro gold shells (μAuSs). The mass analyses of amino acids, sugars, peptides, and their mixtures gave apparent mass peaks for analytes without any significant background interferences. μAuSs afforded a better limit of detection (LOD) and a higher signal-to-noise ratio than gold nanoparticles, which are commonly used for LDI-TOF analysis of small molecules. We believe μAuSs have advantages in terms of simplicity, detection limit, and reproducibility, and therefore, they constitute a significant addition to the organic matrix-free analytical tools that are currently in wide use.
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ABSTRACT: Thiol-containing (bio)molecules, such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), are recognized to be physiologically important and known to be involved in many diseases, such as leucocyte loss, psoriasis, liver damage, and cancer, depending on changes in the cellular level. 1 Particularly, GSH, which exists in high abundance in bio-logical systems, plays key roles in a variety of biological processes including maintenance of intracellular redox activities and cellular homeostasis, xenobiotic metabolism, intracellular signal transduction, and protecting against oxidative stress and toxic species. 2-4 Accordingly, the detec-tion of thiol-containing molecules in samples requires critical selectivity and high sensitivity. For this purpose, various detection techniques, such as gas chromatography, 5 high performance liquid chromatography, 6 capillary electrophoresis, 7 electrochemical detections, 8 and colorimetric detection with fluorescence 9 or Ellman's reagent (5,5'-dithiobis(2-nitro-benzoic acid) or DTNB), have been developed. However, these biothiols have similar physical properties in terms of polarity and solubility, and almost same chemical reactivity in thiol functionality for tagging optical probes. Thus, these similar physical and chemical properties of biothiols lead to poor selectivity in various detection methods. In this regard, mass spectrometry (MS) has recently been utilized for the detection of thiol-containing molecules, since MS analysis provides molecular weights of analytes which are the intrinsic property of molecules, and therefore, affords direct informations of analytes. 10 In addition, MS analysis can easily discriminate between true analyte and background, and can monitor multiple analytes simultaneously, resulting in reduced false positive signals and multiplexing capability. Matrix-assisted laser desorption/ionization (MALDI) is a laser-based soft ionization technique used in mass spectro-metry. It is widely used for the analysis of biomolecules and macromolecules such as proteins, DNA, organic polymers, and dendrimers. However, analysis of small molecules is hampered by an organic matrix requirement due to inter-ference of a matrix in the low mass region. To overcome this issue, surface-assisted laser desorption/ionization mass spectro-metry (SALDI-MS) has been actively studied using various nanoparticles (NPs) and nanostructured surfaces with organic matrix-free format. 11-13 In this paper, we describe a simple method for the selective detection of thiol-containing mole-cules in mixed samples using organic matrix free laser desorption/ionization-time of flight (LDI-TOF) MS with nanostructure embedded gold micro shells (µAuSs). 14 µAuSs possess embossed nanostructures on the surface which allows the desorption and ionization of analytes. 15-17 Furthermore, thiol-containing molecules can be selectively captured on µAuSs by way of a specific gold-thiol inter-action leading to the successful isolation of thiol-containing molecules in mixed samples. Figure 1 shows the schematic presentation of our strategy for selective extraction and analysis of thiol-containing molecules in mixtures. µAuSs are incubated with a mixed sample and thiol-containing molecules in the sample are selectively adsorbed to µAuSs by the gold-thiol interaction. All other molecules except thiols are then washed away, and the isolated thiol-contain-ing molecules are analyzed directly by LDI-TOF MS without use of organic matrices which affords peaks corresponding Figure 1. Schematic presentation of the strategy for selective extraction and analysis of thiol-containing molecules in mixtures. Thiol-containing molecules in mixtures are selectively adsorbed to µAuSs by the Au-thiol interaction and all other molecules except thiols are washed away. The isolated thiol-containing molecules are analyzed directly by LDI-TOF MS which affords peaks corre-sponding to thiol-containing molecules selectively.Bulletin- Korean Chemical Society 09/2012; 33(9). DOI:10.5012/bkcs.2012.33.9.3076 · 0.84 Impact Factor
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ABSTRACT: We report on a simple, fast, and highly sensitive method that allows femtomolar detection of microRNAs (miRNAs) without the need of polymerase chain reaction using a nanoengineered micro gold shell (μAuS) and laser desorption/ionization time-of-flight (LDI–TOF) mass spectrometry (MS). Target miRNAs are selectively captured by a chemically decorated gold chip and a μAuS, which carries with it a large number of small molecules, termed amplification tags (Am-tags). Subsequent LDI–TOF MS analysis allows a highly amplified mass signal of Am-tags for the presence of target miRNAs in a sample, resulting in ultrasensitive detection.Analytical Biochemistry 03/2013; 434(1):199–201. DOI:10.1016/j.ab.2012.11.009 · 2.22 Impact Factor
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ABSTRACT: Analytical applications often require rapid measurement of compounds from complex sample mixtures. High-speed mass spectrometry approaches frequently utilize techniques based on direct ionization of the sample by laser irradiation, mostly by means of matrix-assisted laser desorption/ionization (MALDI). Compounds of low molecular weight are difficult to analyze by MALDI, however, because of severe interferences in the low m/z range from the organic matrix used for desorption/ionization. In recent years, surface-assisted laser desorption/ionization (SALDI) techniques have shown promise for small molecule analysis, due to the unique properties of nanostructured surfaces, in particular, the lack of a chemical background in the low m/z range and enhanced production of analyte ions by SALDI. This short review article presents a summary of the most promising recent developments in SALDI materials for MS analysis of low molecular weight analytes, with emphasis on nanostructured materials based on metals and semiconductors.The Analyst 10/2013; 138(23). DOI:10.1039/c3an01120h · 3.91 Impact Factor