Increasing sensitivity and decreasing spot size using an inexpensive, removable hydrophobic coating for matrix‐assisted laser desorption/ionisation plates

Owen, Stacey J.; Meier, Felix S.; Brombacher, Stephan; Volmer, Dietrich A.

doi:10.1002/rcm.1210

Cited by 47 publications

(50 citation statements)

References 28 publications

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“…To implement this interface, the limit of detection must be improved. One way this can be accomplished is with a hydrophobic MALDI target [53,54] to obtain smaller deposited spot sizes. Under these conditions, the deposition volume can be reduced to achieve low volume fractions with a higher local concentration.…”

Section: Discussionmentioning

confidence: 99%

Development of an automated digestion and droplet deposition microfluidic chip for MALDI-TOF MS

Lee

Musyimi

Soper

et al. 2008

J. Am. Soc. Mass Spectrom.

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An automated proteolytic digestion bioreactor and droplet deposition system was constructed with a plastic microfluidic device for off-line interfacing to matrix assisted laser desorption/ ionization time-of-flight mass spectrometry (MALDI-TOF MS). The microfluidic chips were fabricated in poly(methyl methacrylate) (PMMA), using a micromilling machine and incorporated a bioreactor, which was 100 ILm wide, 100 ILm deep, and possessed a 4 cm effective channel length (400 nL volume). The chip was operated by pressure-driven flow and mounted on a robotic fraction collector system. The PMMA bioreactor contained surface immobilized trypsin, which was covalently attached to the UV-modified PMMA surface using coupling reagents N-(3-dimethylaminopropyl)-N'-ethy1carbodiimide hydrochloride (EDC) and hydroxysulfosuccinimide (sulfo-NHS). The digested peptides were mixed with a MALDI matrix on-chip and deposited as discrete spots on MALDI targets. The bioreactor provided efficient digestion of a test protein, cytochrome c, at a flow rate of 1 ILL/min, producing a reaction time of -24 s to give adequate sequence coverage for protein identification. Other proteins were also evaluated using this solid-phase bioreactor. The efficiency of digestion was evaluated by monitoring the sequence coverage, which was 64%, 35%, 58%, and 47% for cytochrome c, Significant progress has been made toward the development of microchip-based technologies for proteomics through the integration of analytical processes into platforms that can provide rapid identification of proteins and the subsequent characterization of various post-translational modifications [1][2][3][4]. The small sample and reagent requirements, rapid analysis times, high throughput processing capabilities, and low operating costs are among the driving forces for the development of these systems [5][6][7][8]. Different microfluidic devices have been applied to specific aspects of protein processing, in particular, protein purification and separation, protein digestion, and protein identification by mass spectrometry [9].There have been a number of approaches to on-line and off-line matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) integrated to chipbased devices [10][11][12][13][14][15][16][17][18]. The primary advantage of the MALDI approach compared with electrospray ionization (ESI) when coupling to microfluidic chips is the potential for multiplexing [19]. The directional control Address reprint requests to Dr. Kermit K. Murray, Department of Chemistry, Louisiana State University, 232 Choppin Hall, Baton Rouge, LA 70802, USA. E-mail: kkmurray@!su.edu of the ESI spray can be difficult with a high-density array of spray tips. Furthermore, microfluidic chip interfaces to ESI can suffer from stability problems when sprays are started or stopped [20,21]. This limits the speed of moving from one sample to another and therefore, limits throughput.With recent advances in analytical methods for proteomics, attention has been directed toward development of effic...

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Section: Discussionmentioning

confidence: 99%

Development of an automated digestion and droplet deposition microfluidic chip for MALDI-TOF MS

Lee

Musyimi

Soper

et al. 2008

J. Am. Soc. Mass Spectrom.

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“…Hydrophobic target plates can also be used to improve the homogeneous sample/matrix crystallization as well as to achieve a concentration of the sample/matrix crystals onto a smaller area (Schuerenberg et al, 2000;Owen et al, 2003;van Kampen et al, 2008b). In the AnchorChip technology (Schuerenberg et al, 2000), hydrophilic anchors of 200-800 mm in diameter are placed onto a hydrophobic surface to allow more control over the size of the area onto which the sample/matrix crystals are deposited compared to hydrophobic target plates without anchors.…”

Section: B Increasing Homogeneous Sample/ Matrix Crystallizationmentioning

confidence: 99%

Biomedical application of MALDI mass spectrometry for small‐molecule analysis

Kampen

Burgers

Groot

et al. 2010

Mass Spectrometry Reviews

136

102

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Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) is an emerging analytical tool for the analysis of molecules with molar masses below 1,000 Da; that is, small molecules. This technique offers rapid analysis, high sensitivity, low sample consumption, a relative high tolerance towards salts and buffers, and the possibility to store sample on the target plate. The successful application of the technique is, however, hampered by low molecular weight (LMW) matrix-derived interference signals and by poor reproducibility of signal intensities during quantitative analyses. In this review, we focus on the biomedical application of MALDI-MS for the analysis of small molecules and discuss its favorable properties and its challenges as well as strategies to improve the performance of the technique. Furthermore, practical aspects and applications are presented.

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“…In the case of sublimed spots the matrices CHCA, SA, 4-Me-CCA, 4-HO-3-Me-CCA, and 4-HO-3-MeO-CCA were deposited by thermal sublimation in a vacuum chamber with a background pressure of about 10 Ϫ5 mbar through contact masks with 600 m diameter holes. For focusing effects with reduced spot sizes [21] the gold-sputtered aluminum oxide template surfaces were hydrophobically coated before matrix sublimation. The deposited layer thickness per spot was about 3 m. Sample preparation on sublimed spots was carried out as surface preparations with 0.5 L analyte solution using Eppendorf GELoader Tips.…”

Section: Sample Preparation and Measurementmentioning

confidence: 99%

Comparison between vacuum sublimed matrices and conventional dried droplet preparation in MALDI-TOF mass spectrometry

Jaskolla

Karas

Roth

et al. 2009

J. Am. Soc. Mass Spectrom.

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The properties of several cinnamic acid compounds used as matrices for matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) were investigated as standard dried droplet (DD) and vacuum sublimed preparations. The differences between both preparation methods were analyzed with regard to matrix grain size, internal ion energy, initial velocity, analyte intensity, and analyte incorporation depth. Some of the used cinnamic acid derivatives exhibit clearly reduced grain sizes as sublimed preparations compared with standard DD approaches. In these cases higher effective temperatures could be measured accompanied by increased analyte intensities, which can be explained by stronger volatilization processes caused by a hindered heat dissipation resulting in a raised analyte transfer into the gas phase. For all sublimed compounds, a strong increase of the initial ion velocity compared with DD preparations could be measured. Higher initial ion velocities correlate with a decrease in internal ion energy which might be attributed to the very uniform crystal morphology exhibited by sublimed compounds. For sublimed matrices without reduced grain size, at least slightly higher analyte intensities could be detected at raised laser fluences. Analyte accumulation in the uppermost matrix layers or the detected higher ion stability can be explanations for these results. Ever increasing numbers of samples call for automation in high-throughput workflows. One of the key areas for progress in automated MALDI analyses consists of improved sample preparation techniques. Numerous efforts have been conducted for improving the preparation step, e.g., the generation of thin uniform matrix layers with high shot-to-shot reproducibility using the aerospray technique by combination of matrix and nitrocellulose [4] or for analysis of synthetic polymers [5]. Also, electrospray deposition and vacuum deposition were reported to yield homogeneous sample preparations with increased analyte intensities [6 -9]. Matrix deposition by sublimation for MALDI imaging has been reported to yield more intense signals with less alkali adducts compared with the electrospray technique [10]. Additionally, sublimed matrix spots deposited on extremely hydrophobic surfaces described in [11][12][13][14] offer a variety of beneficial properties compared with standard dried droplet (DD) preparations: The main advantage of sublimed matrix spots compared with standard DD preparations are higher analyte sensitivities [14 -17]. This is likely related to the formation of considerably smaller crystals and narrow size distribution of thin-film sublimed matrices, such as ␣-cyano-4-hydroxycinnamic acid (CHCA), compared with DD preparations with comparatively large particle sizes and broader size distribution [15]. As a consequence of this, the specific matrix surface area as well as the amount of potential binding places increases compared with standard DD precipitates, which will result in increased analyte binding properties. Additionally, th...

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Increasing sensitivity and decreasing spot size using an inexpensive, removable hydrophobic coating for matrix‐assisted laser desorption/ionisation plates

Cited by 47 publications

References 28 publications

Development of an automated digestion and droplet deposition microfluidic chip for MALDI-TOF MS

Development of an automated digestion and droplet deposition microfluidic chip for MALDI-TOF MS

Biomedical application of MALDI mass spectrometry for small‐molecule analysis

Comparison between vacuum sublimed matrices and conventional dried droplet preparation in MALDI-TOF mass spectrometry

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