A novel magnet focusing plate for matrix-assisted laser desorption/ionization analysis of magnetic bead-bound analytes

MALDI-TOF MS: A Promising Analytical Approach to Cancer Diagnostics and Monitoring

Cancer remains the second most common cause of death after cardiovascular diseases, accounting for nearly 10 million deaths in 2020. Although the incidence of cancer increases considerably with age, the cancer burden can also be reduced and have a high chance of cure through early detection, appropriate treatment, and care of patients. The development of high-throughput analytical approaches, like matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), contributes to identifying a pool of proteins/peptides as putative biomarkers for the early detection, diagnosis, and tumor progression. The purpose of the current review is to present an updated outline of recent proteome/peptidome research to establish putative cancer biomarkers using MALDI-TOF MS and highlight the applicability of statistical analysis in the oncology field. The pros and cons of MALDI-TOF MS application on cancer diagnostics and monitoring will be discussed, as well as compared with tandem mass spectrometry (MS/MS)-based proteomics (e.g., liquid chromatography–tandem mass spectrometry). In addition, pre-analytical (e.g., sample quality control) and analytical (e.g., sample pre-treatment, instrumental analytical conditions) properties that influence the robustness of MALDI-TOF MS data will be also discussed.

Rapid fabrication of functionalized plates for peptides, glycopeptides and protein purification and mass spectrometry analysis

A rapid and simple approach for fabricating a disposable functionalized membrane on matrix-assisted laser desorption ionization (MALDI) targets, glass, or plastic substrates, without using complex mechanical protocols or chemical reactions, was developed for sample enrichment and mass spectrometry analysis. By coating functionalized-silica particles on a polydimethylsiloxane (PDMS)-coated plate, these particles can form a monolayer of materials on the PDMS membrane for sample handling without peeling off. An octadecyl(C18)-functionalized plate was fabricated by coating porous C18-silica particles on a PDMS-coated plate. The C18 particle-coated PDMS plate (CP plate) has better sensitivity than C18 tips and magnetic nanoparticles, along with a higher sample recovery (64.3 ± 4.9%) compared to the C18 tip method, when analyzing trace amounts of 5 fm BSA digest samples. The CP plate shows significantly higher urea/SDS removal efficiency on the cell lysate proteome compared to C18 tips. The capacity of the C18 spot (∼2.8 mm in diameter) on the CP plate was ∼10 μg of BSA digests. A hydrophilic particle-coated PDMS plate was also fabricated and successfully used for glycopeptide enrichment and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis.

Challenges in biomarker discovery with MALDI-TOF MS

MALDI-TOF MS technique is commonly used in system biology and clinical studies to search for new potential markers associated with pathological conditions. Despite numerous concerns regarding a sample preparation or processing of complex data, this strategy is still recognized as a popular tool and its awareness has risen in the proteomic community over the last decade. In this review, we present comprehensive application of MALDI mass spectrometry with special focus on profiling research. We also discuss major advantages and disadvantages of universal sample preparation methods such as micro-SPE columns, immunodepletion or magnetic beads, and we show the potential of nanostructured materials in capturing low molecular weight subproteomes. Furthermore, as the general protocol considerably affects spectra quality and interpretation, an alternative solution for improved ion detection, including hydrophobic constituents, data processing and statistical analysis is being considered in up-to-date profiling pattern. In conclusion, many reports involving MALDI-TOF MS indicated highly abundant proteins as valuable indicators, and at the same time showed the inaccuracy of available methods in the detection of low abundant proteome that is the most interesting from the clinical perspective. Therefore, the analytical aspects of sample preparation methods should be standardized to provide a reproducible, low sample handling and credible procedure.

Fast quantitative determination of methylphenidate levels in rat plasma and brain ex vivo by MALDI-MS/MS

This study presents a simple and sensitive high-throughput matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry (MALDI-MS/MS) method for ex vivo quantification of methylphenidate (MPH) in rat plasma and brain. The common MALDI matrix alpha-cyano-4-hydroxycinnamic acid was used to obtain an optimal dried droplet preparation. For method validation, standards diluted in plasma and brain homogenate prepared from untreated (control) rats were used. MPH was quantified within a concentration range of 0.1-40 ng/ml in plasma and 0.4-40 ng/ml in brain homogenate with an excellent linearity (R²  ≥ 0.9997) and good precision. The intra-day and inter-day accuracies fulfilled the FDA's ±15/20 critera. The recovery of MPH ranged from 93.8 to 98.5% and 87.2 to 99.8% in plasma and homogenate, respectively. We show that MPH is successfully quantified in plasma and brain homogenate of rats pre-treated with this drug using the internal standard calibration method. By means of this method, a linear correlation between plasma and brain concentration of MPH in rodents pre-treated with MPH was detected. The simple sample preparation based on liquid-liquid extraction and MALDI-MS/MS measurement requires approximately 10 s per sample, and this significantly reduces analysis time compared with other analytical methods. To the best of our knowledge, this is the first MALDI-MS/MS method for quantification of MPH in rat plasma and brain. Copyright © 2015 John Wiley & Sons, Ltd.