Porous Silicon as a Versatile Platform for Laser Desorption/Ionization Mass Spectrometry

Shen, Zhouxin; Thomas, John J.; Averbuj, Claudia; Broo, Klas; Engelhard, Mark H.; Crowell, John E.; Finn, M. G.; Siuzdak, Gary

doi:10.1021/ac000746f

Cited by 345 publications

(314 citation statements)

References 29 publications

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“…An increased surface area can enhance LDI signals [1,2,7,8,10], but comparisons among NPG surfaces showed differences between surface area and LDI efficiency. Although the RSA is larger by the order of NPG #59#49#39#29#1 (refer to Figure 1S, Supporting Information), the LDI signal from NPG #1 was larger than those from NPG #2 and #3.…”

Section: Evaluation and Comparison Of Npg Surfaces For Ldi-tof-msmentioning

confidence: 97%

“…Particles or surfaces with nanostructures have been combined with LDI to improve ionization efficiency and reduce matrix interference [1][2][3][4][5][6][7][8][9][10][11][12][13]. Although many studies have employed nanostructures to improve LDI efficiency and selectivity, relatively few reports have examined how the nanostructure is related to LDI efficiency [9].…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of Nanoporous Gold with Controlled Surface Structures for Laser Desorption Ionization (LDI) Analysis: Surface Area Versus LDI Signal Intensity

Jin

Choi

Kim

et al. 2012

J. Am. Soc. Mass Spectrom.

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The structural effect of a nanoporous gold (NPG) surface on the signal intensities of laser desorption ionization-mass spectrometry (LDI-MS) were investigated using NPG surfaces with controlled structures. The relationship between surface area and LDI efficiency was compared and evaluated. Comparisons between bare flat gold and NPG surfaces show that nanostructures increased LDI efficiency. We also found that the LDI signal decreased with increasing depth of nanoporous layers, thus increasing the surface area. This result agrees with a previous report (Shin J. A. et al., J. Am. Soc. Mass Spectrom. 2010, 21, 989) in which the LDI efficiency of small molecules decreased for ZnO wires with longer lengths. This observation was explained by the penetration and deposition of samples into locations inaccessible to photons because of structural screening. The LDI-MS analysis of oils with NPG surfaces (but without matrix) showed the same trend whereby the NPG with about a 200 nm depth of porous area showed the highest sensitivity. This study clearly shows that the active surface area for solution chemistry can differ from LDI-MS and that NPGs can function as a substrate for LDI oil analysis.

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Section: Evaluation and Comparison Of Npg Surfaces For Ldi-tof-msmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Evaluation of Nanoporous Gold with Controlled Surface Structures for Laser Desorption Ionization (LDI) Analysis: Surface Area Versus LDI Signal Intensity

Jin

Choi

Kim

et al. 2012

J. Am. Soc. Mass Spectrom.

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“…Pollution from chemicals used during the manufacture of the material [18] or during the material storage [27] was envisaged. Extensive washing and drying under vacuum of the silica gel before its usage surprisingly did not allow us to solve this problem.…”

Section: Investigation Of Ldi Processmentioning

confidence: 99%

Laser desorption/ionization mass spectrometry on porous silica and alumina for peptide mass fingerprinting

Shenar

Martinez

Enjalbal

2008

J. Am. Soc. Mass Spectrom.

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We investigated a variant of desorption/ionization on porous silicon (DIOS) mass spectrometry utilizing an aqueous suspension of either porous silica gel or porous alumina (pore size of 60 and 90 Å, respectively). Laser desorption/ionization (LDI) from samples directly deposited on a stainless steel surface without any inorganic substrates was also achieved. Synthetic peptides designed to cover large sequence diversity constituted our model compounds. Sample preparation, including material conditioning, peptide solubilization, and deposition protocol onto standard matrix-assisted laser desorption/ionization (MALDI) probe, as well as ionization source tuning were optimized to perform sensitive reproducible LDI analyses. The addition of either a cationizing agent or an alkali metal scavenger to the sample suspension allowed modification of the ionization output. Comparing hydrophilic silica gel to hydrophobic reversed-phase silica gel as well as increasing material pore size provided further insights into desorption/ionization processes. Furthermore, mixtures of peptides were analyzed to probe the spectral suppression phenomenon when no interfering organic matrix was present. The results gathered from synthetic peptide cocktails indicated that LDI mass spectrometry on silica gel or alumina constitutes a promising complementary method to MALDI in proteomics for peptide mass fingerprinting. [19]. These LDI methods, sometimes referred to as "matrix-free", produce mass spectra that exhibit less matrix ions in the low mass range compared with the chemical noise generated by the organic matrices used in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. Such chemical noise that usually pollutes the low mass range of MALDI mass spectra and that may complicate the detection of small molecules is less pronounced in the DIOS mass spectra.Nevertheless, the drawback of such an approach is in the preparation of the silicon material. To present adequate physical properties [20], silicon surfaces are conditioned via a galvanostatic etching procedure from Si wafer to produce pores with nanometer diameters. Commercially available ready-to-use DIOS-chips can also be mounted on modified MALDI plates [20]. Otherwise, silicon powders (5 to 50 nm particle size) were investigated as a substitute to DIOS chips to make the overall sample preparation simpler and safer [18]. Provided that the appropriate powder preparation was performed (including particle etching by HF, oxidation by HNO 3 , and derivatization of the generated SiOH groups), such silicon nanopowder method was found to exhibit the same characteristics as DIOS mass spectrometry.Porous silicon is a material that presents (1) a large active surface and (2) a strong absorbance in the UV range. Such a form of silicon was thus found particularly suitable for LDI mass spectrometry with irradiation at 337 nm, the pore size and the surface chemical nature being the most important parameters as stated by Siuzdak and coworkers in their early publications on DIOS [20...

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“…A porous silicon surface has also been used for LDI-MS, which is referred to as desorption/ionization on silicon (DIOS) [23][24][25][26][27]. For DIOS-MS, porosity or roughness is presumed to be necessary for desorption/ionization [28,13,29,30].…”

Section: Introductionmentioning

confidence: 99%

Surface-assisted laser desorption/ionization-mass spectrometry using TiO2-coated steel targets for the analysis of small molecules

et al. 2011

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Matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) measurements in the low-molecular mass region, ranging from 0 to 1000 Daltons are very often difficult to perform because of signal interferences originating from matrix ions. In order to overcome this problem, a stainless steel target was coated with a homogeneous titanium dioxide layer. The layer obtained was further investigated for its ability to desorb small molecules, e.g. amino acids, sugars, polyethyleneglycol (PEG 200) or extracts from Cynara scolymus leaves. The stability of the layer was determined by repeated measurements on the same target location, which was monitored by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) before and after surface assisted laser desorption/ionization (SALDI) analysis. In addition, the titanium dioxide layerwas compared with an already published method with titanium dioxide nanopowder as inorganic matrix. As a result of this work, the titanium dioxide layer produced minimal background interference, enabling simple interpretation of the detected mass spectra. Furthermore, the TiO2 coating provides a target that can be reused many times for SALDI-MS measurements.

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Porous Silicon as a Versatile Platform for Laser Desorption/Ionization Mass Spectrometry

Cited by 345 publications

References 29 publications

Evaluation of Nanoporous Gold with Controlled Surface Structures for Laser Desorption Ionization (LDI) Analysis: Surface Area Versus LDI Signal Intensity

Evaluation of Nanoporous Gold with Controlled Surface Structures for Laser Desorption Ionization (LDI) Analysis: Surface Area Versus LDI Signal Intensity

Laser desorption/ionization mass spectrometry on porous silica and alumina for peptide mass fingerprinting

Surface-assisted laser desorption/ionization-mass spectrometry using TiO2-coated steel targets for the analysis of small molecules

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