Mesoporous tungsten titanate as matrix for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis of biomolecules

The quest for improved reproducibility in MALDI mass spectrometry

Reproducibility has been one of the biggest hurdles faced when attempting to develop quantitative protocols for MALDI mass spectrometry. The heterogeneous nature of sample recrystallization has made automated sample acquisition somewhat "hit and miss" with manual intervention needed to ensure that all sample spots have been analyzed. In this review, we explore the last 30 years of literature and anecdotal evidence that has attempted to address and improve reproducibility in MALDI MS. Though many methods have been attempted, we have discovered a significant publication history surrounding the use of nitrocellulose as a substrate to improve homogeneity of crystal formation and therefore reproducibility. We therefore propose that this is the most promising avenue of research for developing a comprehensive and universal preparation protocol for quantitative MALDI MS analysis. © 2016 Wiley Periodicals, Inc. Mass Spec Rev 37:217-228, 2018.

High-efficiency nano/micro-reactors for protein analysis

This article reviews the recent advances regarding the development of nanomaterial-based nanoreactors and microfluidic droplet reactors and their applications in protein analysis.

Nanomaterial-assisted laser desorption ionization for mass spectrometry-based biomedical analysis

Nanomaterials have been widely used to assist laser desorption ionization of biomolecules for mass spectrometry analysis. Compared with classical matrix-assisted laser desorption ionization, strategies based on nanomaterial-assisted ionization generate a clean background, which is of great benefit for the qualitative and quantitative analysis of small biomolecules, such as therapeutic and diagnostic molecules. As label-free platforms, they have successfully been used for high-throughput enzyme activity/inhibition monitoring and also for tissue imaging to map in situ the distribution of peptides, metabolites and drugs. In addition to widely used porous silicon nanomaterials, gold nanoparticles can be easily chemically modified by thiol-containing compounds, opening novel interesting perspectives. Such functionalized nanoparticles have been used both as probes to extract target molecules and as matrices to assist laser desorption ionization for developing new enzyme immunoassays or for studying DNA hybridization. More recently, semiconductor nanomaterials or quantum dots acting as photosensitive centers to induce in-source redox reactions for proteomics and to investigate biomolecule oxidation for metabolomics have been shown to offer new analytical strategies.

Titanium dioxide anatase as matrix for matrix-assisted laser desorption/ionization analysis of small molecules

The use of inorganic species as assisting materials in matrix-assisted laser desorption/ionization (MALDI) analysis is an alternative approach to avoid interfering matrix ions in the low-mass region of the mass spectra. Reports of the application of inorganic species as matrices in MALDI analysis of small molecules are, however, scarce. Nevertheless, titanium dioxide (TiO(2)) powder has been reported to be a promising matrix medium. In this study we further explore the use of TiO(2) as a matrix for the MALDI analysis of low molecular weight compounds. We present results showing that nanosized TiO(2) anatase and TiO(2) rutile perform better as MALDI matrices than a commercial TiO(2) anatase/rutile mixture. Moreover, when using nanosized TiO(2) anatase as a matrix, high-quality mass spectra can be obtained with strong analyte signals and weak or non-existing matrix interference ions. Furthermore, our results show that the phase type plays an important role in the application of TiO(2) as a MALDI matrix.