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.
Highlights
Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is widely used to analyze biomolecules such as proteins and deoxyribonucleic acid (DNA) with a high molecular weight (Karas and Hillenkamp 1988; Tanaka et al 1988; Guinan et al 2015; Lu and Cai 2012)
The results indicated that the mass intensity and the signal-tonoise ratio (S/N) ratio were significantly increased after mixing cyano-4-hydroxycinnamic acid (CHCA) with solid matrices of graphene, Carbon nano‐ tube (CNT), Pt NPs, and P25
The mass peaks of the combimatrices consisting of CHCA and solid matrices of graphene, CNTs, P25, and Pt NPs were higher than those of the conventional organic matrix of CHCA
Summary
Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is widely used to analyze biomolecules such as proteins and deoxyribonucleic acid (DNA) with a high molecular weight (Karas and Hillenkamp 1988; Tanaka et al 1988; Guinan et al 2015; Lu and Cai 2012) Ultraviolet-absorbing materials such as CNTs, Pt NPs, and P25 (TiO2) with high thermal conductivity (Table 1) will be tested as solid matrices to optimize the combi-matrix for the quantitative analysis of T4, which can effectively absorb the laser radiation to enhance the desorption process (Choi et al 2018; Banazadeh et al 2018; Rodríguez et al 2015; Chen et al 2016). Quantitative analysis of T4 will be conducted for T 4 samples in human serum using each combi-matrix
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