Matrix-free and material-enhanced laser desorption/ionization mass spectrometry for the analysis of low molecular weight compounds

Abstract

The application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) for the analysis of low molecular weight (LMW) compounds, such as pharmacologically active constituents or metabolites, is usually hampered by employing conventional MALDI matrices owing to interferences caused by matrix molecules below 700 Da. As a consequence, interpretation of mass spectra remains challenging, although matrix suppression can be achieved under certain conditions. Unlike the conventional MALDI methods which usually suffer from background signals, matrix-free techniques have become more and more popular for the analysis of LMW compounds. In this review we describe recently introduced materials for laser desorption/ionization (LDI) as alternatives to conventionally applied MALDI matrices. In particular, we want to highlight a new method for LDI which is referred to as matrix-free material-enhanced LDI (MELDI). In matrix-free MELDI it could be clearly shown, that besides chemical functionalities, the material's morphology plays a crucial role regarding energy-transfer capabilities. Therefore, it is of great interest to also investigate parameters such as particle size and porosity to study their impact on the LDI process. Especially nanomaterials such as diamond-like carbon, C(60) fullerenes and nanoparticulate silica beads were found to be excellent energy-absorbing materials in matrix-free MELDI.

Direct Mass Spectrometry-Based Approaches in Metabolomics

“…A variety of surface properties have been studied for matrix-free ionization of small molecules, for example: diamond nanowires [17] sol-gel derived silver-nanoparticles-impregnated thin biofilm [18], nanoporous gallium nitride-silver nanoparticles [19], metal oxide surfaces [20], nanofilament silicon [21], etc. Comprehensive reviews of innovative technologies using energy-absorbing materials for matrix-free LDI-MS have been recently published [22][23][24].…”

Membrane-based detection of lead ions in seawater, urine and drinking straws through laser desorption/ionization

“…To improve the desorption and ionization efficiency of analytes, various organic matrices (e.g., 2,5-dihydroxybenzoic acid, 3,5-dimethoxy-4-hydroxycinnamic acid, ␣-cyano-4-hydroxycinnamic acid, 3-hydroxypicolinic acid) can been employed in LDI-MS to allow the analyses of carbohydrates, nucleic acids, peptides, and proteins [21][22][23]. When performing analyses through matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), these matrices are usually mixed to excess to avoid fragmentation of the analytes under laser irradiation [24][25][26].…”

“…Laser desorption/ionization (LDI) has emerged as powerful and versatile tool in mass spectrometry (MS) for the analysis of marcomolecules [21,22]. To improve the desorption and ionization efficiency of analytes, various organic matrices (e.g., 2,5-dihydroxybenzoic acid, 3,5-dimethoxy-4-hydroxycinnamic acid, ␣-cyano-4-hydroxycinnamic acid, 3-hydroxypicolinic acid) can been employed in LDI-MS to allow the analyses of carbohydrates, nucleic acids, peptides, and proteins [21][22][23].…”

Analyses of functional polymer-modified nanoparticles for protein sensing by surface-assisted laser desorption/ionization mass spectrometry coupled with HgTe nanomatrices

“…Nanoparticle (NP)-and nanosubstrate-based surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) techniques are being used more widely to mediate desorption processes; they operate with several attractive features, including ready preparation of homogeneous samples, excellent analyte-loading capacity, high salt tolerance, and low background noise in the low mass-to-charge region [15][16][17][18][19][20][21]. The main shortcoming when conducting SALDI-MS with NPs as the matrix for the analysis of biomacromolecules and polymers is inefficient desorption and ionization, due to the strong nonspecific interactions between large molecules and NPs [22,23].…”