Iron Oxide Nanoparticles Matrix And Mimetic Tissue Section For Laser Desorption Ionization Mass Spectrometry And Mass Spectrometry Imaging

Laser desorption/ionization mass spectrometry imaging（LDI-MSI）,as a new molecular imaging technology,can directly obtain the composition,content and spatial distribution information of a large number of known or unknown compounds on the tissue surface.In the thesis,we investigated the iron oxide nanomatrix for analysing small molecules in LDI-MS and use mimetic tissue sections for evaluating the quantitative result of mass spectrometry imaging using Fourier transform cyclotron resonance mass spectrometry（FT-ICR-MS）instrument.（1）The iron oxide nanoparticle matrix was synthesized by mixing Fe Cl₂·4H₂O and 3-aminopropyltriethoxysilane.We used iron oxide nanomatrix to LDI-MS analyse oligosaccharides,plant hormones,flavonoids,triglycerides,phospholipids,amino acids and other small molecular compounds.The results showed that iron oxide nanomatrix had good stability and low background noise.By examining the effect of the experimental conditions in the positive ion mode,the laser energy was selected as 70%,and the average spectrum was accumulated 30 times.The spotting method of adding matrix first and then sample was applied with 1:1 equal volume.The results showed that each intra-point reproducibility（RSD）of glutamic acid,glucose,sucrose,abscisic acid and triolein was less than 2.8%and the inter-point repeatability was less than 5.2%under the selected conditions.The detection limits of sucrose,raffinose,genistein,abscisic acid,1,2-dipalmitoyl-sn-glycero-3-phosphorylcholine,triolein,tripalmitin and glutamic acid were 2.3μg/m L,1.9μg/m L,2.3μg/m L,1.4μg/m L,6.7μg/m L,13μg/m L,13μg/m L and 19μg/m L,respectively.In the concentration range of 0.05-1.0 mg/m L,the linear correlation coefficient R²>0.993 of the above-mentioned eight samples was determined,which shows a good potential for quantitative analysis.LDI-MSI was used to analyze the small molecular components in soybean,and the mass spectrometry peaks were identified.The results showed that the oligosaccharides were mainly located at the outer parts of the cotyledons and the radicle,and the triglycerides were more distributed in the cotyledons.The influencing factors in the preparation process of nanomaterials are discussed,and the preparation methods in the literature has been improved.（2）We prepared soybean mimetic tissue sections.The effects of experimental parameters such as section thickness,matrix deposition method and laser energy on mass spectrometry analysis were investigated.Using the selected experimental conditions,the homogeneity and repeatability of soybean mimetic tissue sections were investigated by adding methyl red reagent.The results shows that the non-tissue block staining in soybean tissue homogenate reached to 83.4%,the intra-section RSD of mass spectrometry peak intensity in mimetic tissue sections of soybean homogenate was less than 11.6%,and the inter-section repeatability RSD was less than 12.8%.The linear correlation coefficient R²>0.996 between the peak intensity and the concentration of added glucose in the homogenate was determined in the range of 2.5-25 mg/g.The added glucose content in the mimetic tissue sections measured by LDI-MS was5.4 mg/g,and the actual glucose concentration in the mimetic tissue sections was 6.2 mg/g.The error was basically in line with the proportion of tissue blocks in soybean tissue homogenate,which was 16.6%.The contents of disaccharides,tetrasaccharide and tetrasaccharide in soybean were determined approximately as 3.9 mg/g～10 mg/g using the standard curve generated by monosaccharides.