@phdthesis{
author = "Popović, Iva A.",
year = "2017",
abstract = "Izvod: MALDI TOF (Matrix Assisted Laser Desorption and Ionization Time-Of-Flight) masenaspektrometrija je meka jonizaciona tehnika koja se prvenstveno koristi za analizubiomolekula (proteina i nukleinskih kiselina) i omogućava detekciju molekula uzveoma nizak stepen fragmentacije. Kako bi se sprečila/ublažila fragmentacijaizazvana direktnom ekscitacijom laserom, uzorak se meša sa matricama koje imajuvisok apsorpcioni koeficijent u oblasti u kojoj laser emituje. Primarno su sekoristile organske, „tradicionalne“ matrice. Pored brojnih prednosti, organskematrice pokazuju i značajne mane koje onemogućavaju primenu MALDI masenespektrometrije za kvantitativnu analizu molekula i sprečavaju detekciju molekulamalih masa manjih od 1000 Da. Kako se u ovoj grupi molekula nalaze i različitibiološki značajni molekuli (metaboliti) postoji potreba za prevazilaženjemnedostataka organskih matrica.Jedan od najranije primenjenih načina je zamena organskih matrica neorganskimjedinjenjima i/ili nanočesticama (supstratima). Koriste se različiti supstrati nabazi ugljeničnih polimera i sol-gel polimerne strukture na bazi silicijum dioksida.Upotreba nanostrukturnih supstrata u metodi koja je nazvana SALDI (Surface AssistedLaser Desorption and Ionization) u poslednjoj deceniji je predmet velikog brojapublikovanih radova. Međutim, nanočestice od metala i oksida metala, kao što su Au,Pt, Ag, ZnO, Fe i MnO2/MnO3, nude prednost u odnosu na ostale materijale - stabilnijesu u vazduhu i poseduju visoku provodljivost. Prednost nanočestica je apsorpcijaenergije lasera i efikasan prenos energije do uzorka. Istakle su se nanočestice odtitan(IV)-oksida zbog svoje dostupnosti, netoksičnosti i niske cene, što je takođepredmet mnogih publikovanih radova. Osim navedenih osobina, titan(IV)-oksid jepoluprovodnik sa dobrom UV apsorpcijom. Generalno, TiO2 snažno apsorbuje UVsvetlost (ima znatnu širinu energetske barijere, 3,2 eV) azotnog lasera koji se koristiu MALDI TOF masenoj spektrometriji, ali proces pripreme nanočestica TiO2verovatno ima snažan uticaj na apsorpciju jer ona zavisi od veličine, oblika i sastavačestica. Površina, a posredno i veličina i oblik kristala utiču na analitičkeperformanse i jonizacionu efikasnost u SALDI masenoj spektrometriji.U ovoj doktorskoj disertaciji korišćeni su nanokristali TiO2 različite veličinei oblika: koloidne nanočestice TiO2 (TiO2 NČ) prosečnog dijametra 5 nm, elipsoidnenanočestice TiO2 (TiO2 ENČ) dužine 40-50 nm, lateralne dimenzije 14-16 nm inanotube TiO2 (TiO2 NT) dužine od 100 do 150 nm i prosečnog dijametra od 11 nm.Molekuli na kojima je bila testirana potencijalna primena nanokristala su biološkiaktivni molekuli malih masa: amino-kiseline (L-cistein, L-alanin, DL-metionin),tripeptid glutation, polni steroidni hormoni (estradiol, testosteron, progesteron),ugljeni hidrati (D-(+)-glukoza, D-(+)-maltoza, rafinoza, arabinoza, β-ciklodekstrin),limunska kiselina, deksametazon (deksazon), vitamini (vitamin A i vitamin E)., Summary:MALDI TOF (Matrix-Assisted Laser Desorption and Ionization Time-Of-Flight) massspectrometry is soft ionization technique. Primarily, this technique was used for the analysis ofbiomolecules such as proteins and nucleic acids with low level of their fragmentation. In orderto prevent/reduce fragmentation of analyzed molecules, induced with direct excitation withlaser, samples are mixed with matrix molecules. Matrix has high absorption coefficient in therange of the laser emission. In spite of numerous advantages, there are serious drawbacks ofthe matrices, and because of that they cannot be used for quantitative MALDI massspectrometric analysis and for the detection of small molecules (molecular mass less than 1000Da). In this group of molecules (mass less than 1000 Da) there are various biologically activemolecules (metabolites), so there is a great need to overcome disadvantages of the applicationof organic matrices.Considerable efforts have been made to overcome the above mention problems andseveral alternative approaches have been developed: an organic-matrix-free approach in whichthe substrates, usually nanoparticles act as a matrix. Many are in use: graphite, silica gel, carbonpowder, activated carbon, graphene, porous silicon, and many more.The term SALDI (Surface-Assisted Laser Desorption and Ionization) was coined todesignate the techniques that use nanostructured substrates. The use of various nanoparticlesas substrates in SALDI MS has attracted a lot of attention in the last decade. Nanoparticlesabsorb the laser energy and then rapidly transfer to analyzed molecule. However, the substratesprepared from materials based on metal-oxides (Аu, Pt, Ag, ZnO, Fe and MnO2/MnO3) aremore stable in the air and have a high conductivity. Titanium(IV)-oxide (TiO2) is consideredto be a good candidate for SALDI substrate since it is readily available, chemically stable, nontoxicand inexpensive material. Titanium(IV)-oxide is a semiconductor with high absorptivityof UV light of nitrogen laser (have a large band gap 3.2 eV) which is used in MALDI TOFmass spectrometry, but the method of synthesis of TiO2 nanocrystal have a great impact onabsorption because this phenomena depends on size, shape and composition of nanoparticles.In this doctoral thesis, the applicability of TiO2 nanocrystals of different size and shape wastested. Colloidal TiO2 nanoparticles (NPs, average diameter ~ 5 nm), TiO2 prolatenanospheroids (PNSs, length: 40–50 nm, the lateral dimension: 14–16 nm) and TiO2 nanotubes(NTs, length: 100-150 nm, average diameter 11 nm) were used as substrates for potentialSALDI TOF MS quantitative analysis of low mass molecules. The analyzed molecules werebiologically active molecules with small molecule mass (Mm less than 1000 Da): amino acids(L-cysteine, L-alanine, DL-methionine), tripeptide glutathione, sex steroid hormones (estradiol,testosterone, progesterone), carbohydrates (D-(+)-glucose, D-(+)-maltose, raffinose, arabinose,β-cyclodextrin), citric acid, dexamethasone (dexasone), vitamins (vitamin А and vitamin Е).",
publisher = "Универзитет у Крагујевцу, Природно-математички факултет",
journal = "Универзитет у Крагујевцу",
title = "Ispitivanje primene neorganskih supstrata na bazi nanokristala TiO2 za detekciju i kvantifikaciju malih molekula SALDI TOF masenom spektrometrijom",
url = "https://hdl.handle.net/21.15107/rcub_nardus_7630"
}