In the search for alternative inert surfaces replacing silicon chips in Desorption/Ionization On porous Silicon (DIOS)-like mass spectrometry analyses, nanostructured silicon-based NALDI chips were evaluated in Laser Desorption/Ionization (LDI) of peptides. Comparisons were made using commercially available DIOS chips (MassPREP-DIOS-target), amorphous carbon powder from lead pencil and porous silica gel used for chromatographic purposes as reference supports. A set of synthetic model peptides presenting variable amino acid sequences of various lengths was analyzed under all conditions. The LDI responses of the four 'matrix-free' techniques were compared, especially in terms of peptide detection sensitivity and overall experiment robustness.
[Show abstract][Hide abstract] ABSTRACT: This study presents a new, simple, and low-cost technique to fabricate a nanocluster silicon (NCSi) surface on planar silicon using a micro-scale direct current (DC) discharge under ambient conditions. The method requires no masks, chemicals, vacuum environment, or laser, but only a high-voltage supply. The NCSi surfaces, characterized by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy, consist of oxidized silicon nanoclusters 50-200 nm in diameter, likely formed by melting due to high temperatures in the discharge. The minimum size of the NCSi spot is determined by the size of the discharge tip (approximately 90 microm). Arbitrary NCSi areas can be produced on a silicon wafer by moving the discharge needle on the surface with the help of a computer-controlled xyz stage. NCSi surfaces can also be formed on three-dimensional (3D) surfaces, as demonstrated with silicon micropillars. NCSi surfaces can be used, for example, in various analytical applications. In this study, we demonstrate their use as sample plates in the analysis of drugs and peptides with desorption/ionization on silicon-mass spectrometry (DIOS-MS).
Lab on a Chip 04/2010; 10(13):1689-95. DOI:10.1039/b927181c · 6.12 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Nanostructure-assisted laser desorption/ionization time-of-flight mass spectrometry (NALDI-TOFMS) has been developed recently as a matrix-free/surface-assisted alternative to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The NALDI surface of silicon nanowires is already very effective for the analysis of small to medium sized, polar organic molecules in positive ion mode. The current study examined this technology for the analysis of several nonpolar organic, organometallic, and ionic compounds in positive ion mode, as well as a fluorinated compound and various acids in negative ion mode. NALDI data are compared and contrasted with MALDI data for the same compounds, and the higher sensitivity of NALDI is highlighted by the successful characterization of two porphyrins for a sample amount of 10 amol per spot.
Journal of the American Society for Mass Spectrometry 04/2010; 21(7):1256-9. DOI:10.1016/j.jasms.2010.03.038 · 2.95 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mass spectrometry imaging of tissue-lipid transfers without MALDI matrix is demonstrated. Commercially available nanostructured surfaces (nano-assisted laser desorption-ionization or NALDI) are used as substrates for imprinting of tissue sections. The lithographic transfers are then washed and the two-dimensional distribution of the lipids is imaged by laser desorption-ionization mass spectrometry. The NALDI imaging of lipid transfers is compared with standard MALDI imaging of matrix-coated tissue sections. The obtained images are of the same quality, and no spatial information is lost due to the imprinting process. NALDI imaging is faster due to the absence of the time-consuming matrix deposition step, and the NALDI mass spectra are less complex and easier to interpret than standard MALDI. In this particular application example, NALDI mass spectrometry is able to identify the same lipid species as MALDI mass spectrometry and provides better distinction between kidney and adrenal gland tissues based on the lipid analysis.
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