Laser desorption/ionization mass spectrometry of L-thyroxine (T4) using combi-matrix of α-cyano-4-hydroxycinnamic acid (CHCA) and graphene

Abstract

An optimal combi-matrix for MALDI-TOF mass spectrometry was presented for the analysis of L-thyroxine (T4) in human serum. For the selection of the optimal combi-matrix, several kinds of combi-matrices were prepared by mixing the conventional organic matrix of CHCA with nanomaterials, such as graphene, carbon nanotubes, nanoparticles of Pt and TiO2. In order to select the optimal combi-matrix, the absorption at the wavelength of laser radiation (337 nm) for the ionization of sample was estimated using UV–Vis spectrometry. And, the heat absorption properties of these combi-matrices were also analyzed using differential scanning calorimetry (DSC), such as onset temperature and fusion enthalpy. In the case of the combi-matrix of CHCA and graphene, the onset temperature and fusion enthalpy were observed to be lower than those of CHCA, which represented the enhanced transfer of heat to the analyte in comparison with CHCA. From the analysis of optical and thermal properties, the combi-matrix of CHCA and graphene was selected to be an optimal combination for the transfer of laser energy during MALDI-TOF mass spectrometry. The feasibility of the combi-matrix composed of CHCA and graphene was demonstrated for the analysis of T4 molecules using MALDI-TOF mass spectrometry. The combi-matrix of CHCA and graphene was estimated to have an improved limit of detection and a wider detection range in comparison with other kinds of combi-matrices. Finally, the MALDI-TOF MS results of T4 analysis using combi-matrix were statistically compared with those of the conventional immunoassay.

Carbon-Based Nanoparticles and Their Surface-Modified Counterparts as MALDI Matrices

“…Improved standard deviation and linearity were observed when CHCA and DHB were spotted on the graphene surface instead of a stainless steel target plate . In another study, a mixture of graphene and CHCA solution was used as a MALDI matrix and showed higher UV absorption at the applied laser wavelength compared to CHCA alone . The higher energy absorption led to a lower LOD and wider detection range for the graphene and CHCA mixture …”

Laser-Assisted Desorption/Ionization Mass Spectrometry Using Nanoporous SiO2 Aerogels for the Diagnosis of Colon Cancer

“…LDI-ToF MS was performed with organic (CHCA), SiO 2 aerogel, and a mixture of SiO 2 aerogel and organic matrices as in previous works. 15 The prepared matrices (0.5 μL) were dispensed dropwise onto the SUS target plate and dried, and 0.5 μL sample solution was then added dropwise onto the spot. The MS analysis was conducted after drying the sample spots at room temperature.…”

“…11 Because inorganic materials are not fragmented and produce mass peaks by the laser radiation during measurement, the inorganic matrices have been effectively used for the quantitative analysis of small molecules, such as metabolites, drugs, and neurotransmitters. 4,8,12,13 Inorganic matrices have previously been fabricated using carbon-based nanomaterials such as carbon nanotubes, graphenes, 14,15 semiconductorbased nanomaterials such as Si, SiO 2 , ZnO, SnO 2 , and TiO 2 , 16−20 and metal nanoparticles such as gold, silver, and platinum. 21−23 Porous structures fabricated from polymers and inorganic materials have also been applied in small molecule analysis.…”

“…This method has been called laser desorption/ionization mass spectrometry (LDI-MS) . Because inorganic materials are not fragmented and produce mass peaks by the laser radiation during measurement, the inorganic matrices have been effectively used for the quantitative analysis of small molecules, such as metabolites, drugs, and neurotransmitters. ,,, Inorganic matrices have previously been fabricated using carbon-based nanomaterials such as carbon nanotubes, graphenes, , semiconductor-based nanomaterials such as Si, SiO 2 , ZnO, SnO 2 , and TiO 2 , − and metal nanoparticles such as gold, silver, and platinum. − Porous structures fabricated from polymers and inorganic materials have also been applied in small molecule analysis. ,, The concept of “Combi-matrix” has been also reported for LDI-MS by mixing organic matrices (α-4-hydroxycinnamic acid (CHCA), 2,5-dihydroxybenzoic acid (DHB), and so on) and other kinds of materials, such as sol–gel derived film by tetraethyl orthosilicate (TEOS), SU-8 photoresist-based polymer, and graphite. − These groups reported that these kinds of “Combi-matrix” could be applicable for the analysis of amino acids, peptides, and small proteins.…”

Simultaneous analysis of acylcarnitines using MALDI-TOF mass spectrometry based on a parylene matrix chip

“…19 However, organic matrices are ionized and fragmented by laser irradiation, and generate unreproducible background noise at a low m/z range (m/z < 500), which hinders small molecule analysis. [20][21][22][23] Additionally, the organic matrix and analyte form inhomogeneous spots on the plate after drying as a result of the "coffee ring effect". 24 In addition, laser irradiation produces different results even when analyzing the same sample spot, which makes quantification difficult using a conventional organic matrix.…”