Surface-assisted laser desorption/ionization

Surface-assisted laser desorption/ionization (SALDI) is a soft laser desorption technique used for mass spectrometry analysis of biomolecules, polymers, and small organic molecules. In its first embodiment Koichi Tanaka used a cobalt/glycerol liquid matrix and subsequent applications included a graphite/glycerol liquid matrix as well as a solid surface of porous silicon. At present laser desorption/ionization methods using other inorganic matrices such as nanomaterials are often regarded as SALDI variants. As an example, silicon nanowires as well as Titania nanotube arrays (NTA) have been used as substrates to detect small molecules. SALDI is used to detect proteins and protein-protein complexes. A related method named 'ambient SALDI' - which is a combination of conventional SALDI with ambient mass spectrometry incorporating the direct analysis real time (DART) ion source has also been demonstrated. SALDI is considered one of the most important techniques in MS and has many applications. Surface-assisted laser desorption/ionization (SALDI) is a soft laser desorption technique used for mass spectrometry analysis of biomolecules, polymers, and small organic molecules. In its first embodiment Koichi Tanaka used a cobalt/glycerol liquid matrix and subsequent applications included a graphite/glycerol liquid matrix as well as a solid surface of porous silicon. At present laser desorption/ionization methods using other inorganic matrices such as nanomaterials are often regarded as SALDI variants. As an example, silicon nanowires as well as Titania nanotube arrays (NTA) have been used as substrates to detect small molecules. SALDI is used to detect proteins and protein-protein complexes. A related method named 'ambient SALDI' - which is a combination of conventional SALDI with ambient mass spectrometry incorporating the direct analysis real time (DART) ion source has also been demonstrated. SALDI is considered one of the most important techniques in MS and has many applications. Koichi Tanaka performed the first successful SALDI experiments on proteins, subsequently Sunner and Chen used graphite particles of 2-150 μm in size as a substrate and solutions of analytes in glycerol. They were able to analyze low molecular weight analytes, peptides, and small proteins by soft ionization technique. Then they developed an approach called SALDI-MS, where a thin layer of activated carbon particles fixed on aluminum support in which the surface and the surface structure were critical in desorption and ionization Since then, the research was focusing on introducing novel nanomaterials as substrates, to enhance the sensitivity, broad the mass range and expanding the categories of samples that can be analyzed using this technique. SALDI was introduced as a promising method with potential applications in systems biology, particularly metabolomics. The introduction of nanomaterials as SALDI substrates attracted researchers in analytical chemistry. Such materials include carbon nanotubes (CNTs), metallic nanoparticles like Ag, Pt, Au, and nanostructured surfaces. This development of substrates allowed for further development of SALDI. The development of desorption/ionization on silicon (DIOS)-MS in particular, and subsequently nanostructure-initiator mass spectrometry (NIMS) and nano-assisted laser desorption/ionization (NALDI), has also attracted the attention of analytical scientists. These methods have since become a benchmark for semiconductor-based SALDI research. The main principle of SALDI relies on a medium that absorbs energy from a laser and then transfers the energy to the target sample. This class of techniques where the bulk of energy goes to the substrate instead of the sample molecules is known as soft ionization techniques. The development of SALDI started as a modification of matrix-assisted laser desorption/ionization (MALDI). The former technique suffered from ionization interference from the matrix molecules of MALDI. SALDI substituted an active surface of specific substrates, usually made of inorganic components, for the organic matrix of MALDI.