Analiza lipidnih ovojev okrog nanodelcev z elektronsko paramagnetno resonanco

Urh, Žiga (author), Ravnik, Miha (mentor), Štrancar, Janez (comentor)

V tem delu smo razvili metodo opazovanja in analize lipidnih ovojev okrog nanodelcev z elektronsko paramagnetno resonanco (EPR). Uporabili smo jo za analizo lipidnih ovojev okrog nanocevk titanovega dioksida in ogljikovih nanocevk. Metoda terja označevanje lipidnih ovojev z molekulami spinskih označevalcev, ki omogočajo zajem spektrov EPR. Uporabili smo šest različnih molekul spinskih označevalcev in vrednotili njihovo primernost za opazovanje lipidnih ovojev. Z računalniško analizo spektrov smo določili gibalne vzorce lipidov v preučevanih vzorcih in stopnjo ureditve lipidnih molekul na stiku med nanodelci in lipidnim dvoslojem. Kompleksne rezultate računalniške obdelave spektrov smo medsebojno primerjali s pomočjo konformacijske entropije, ki jih prevede v eno samo fizikalno količino. Opazili smo, da je uspešnost zaznave urejanja lipidnih molekul ob nanomaterialu odvisna od vrste površine in kemijske strukture označevalcev. Eksperimenti so pokazali, da urejanje ob hidrofilni površini nanocevk titanovega dioksida zaznamo le z označevalcem GluSL Stearate, katerega kemijska struktura omogoča zadostno molekularno bližino med označevalskimi molekulami in površino nanomateriala. Urejanje lipidnih molekul ob hidrofobni površini ogljikovih nanocevk smo opazili z vsemi uporabljenimi označevalci. Izkazalo se je, da je v tem primeru stopnja zaznane ureditve odvisna od položaja nitroksidnega obroča na molekulah označevalca, velikost označevalskih molekul in drugih funkcionalnih skupin na označevalcih. Zaradi vse širše uporabe nanomaterialov v vsakdanjem življenju ti prihajajo v stik z živimi organizmi. Njihovi vplivi na okolje in zdravje so večinoma neznani ali pa slabo razumljeni. Povezava med lastnostmi nanodelcev in njihovo škodljivostjo ni dobro znana, saj ne poznamo vseh mehanizmov, ki do škodljivosti privedejo. Ker je ovijanje lipidnih dvoslojev okoli nanodelcev eden izmed pojavov, ki jih lahko opazimo na stiku med nanodelci in biološkimi membranami, bi lahko njegovo razumevanje vodilo k boljši napovedljivosti toksičnosti nanomaterialov. Z rezultati v tem magistrskem delu smo pokazali, da je spektroskopija EPR primerno orodje za analizo lipidnih ovojev okrog nanodelcev. Uporabljena metoda bi zato lahko postala eden izmed pripomočkov pri določevanju škodljivosti nanomaterialov.

• Language: Slovenian
• Keywords: EPR, nanodelci, lipidne membrane, lipidni ovoji, spinski označevalci, konformacijska entropija
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FMF - Faculty of Mathematics and Physics
• Year: 2018
• PID: 20.500.12556/RUL-101429
• COBISS.SI-ID: 3208804
• Publication date in RUL: 02.06.2018

URH, Žiga, 2018, Analiza lipidnih ovojev okrog nanodelcev z elektronsko paramagnetno resonanco [online]. Master’s thesis. [Accessed 26 April 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=101429

Secondary language

• Language: English
• Title: Analysis of lipid wrapping around nanoparticles with electron paramagnetic resonance

Abstract

Herein we developed a method for observation and analysis of lipid wrapping around nanoparticles with electron paramagnetic resonance (EPR). It was used for analysis of lipid wrapping around titanium dioxide and carbon nanotubes. For acquisition of EPR spectra, this method requires labeling of lipid wraps with spin-labeling molecules. We used six different spin-labeling molecules and determined their usefulness for lipid wrapping observation. With computational analysis of the spectra, we determined motional patterns of lipids in the samples and strength of molecular ordering at the interface between nanoparticles and lipid bilayers. We used conformational entropy to compare complex results of computational analysis of the spectra. We found out that success of detection of lipid ordering on nanomaterial surface is determined by surface type and chemical structure of spin labels. In case of hydrophilic surface of titanium dioxide nanotubes, lipid ordering was only observed for spin label GluSL Stearate. Molecular proximity between nanomaterial and spin labels for this labeling molecule is enabled by the molecule’s chemical structure. In case of hydrophobic surface of carbon nanotubes, all of the spin labels used in the experiments observed lipid ordering. The degree of detected ordering was found out to be dependent on position of nitroxide group, size of spin-labeled molecules and other functional groups attached to the spin labels. Increasing use of nanomaterials in everyday life has led to increased exposure of living organisms to nanoparticles. Their effects on environment and health is mostly unknown or poorly understood. Relationship between properties of nanoparticles and their harmfulness is not well-known since the mechanisms that lead to harmfulness are not understood. Lipid wrapping around nanoparticles is one of the phenomena that can be observed at contact between nanoparticles and biological membranes. Understanding of lipid wrapping could lead to improved predictability of nanomaterial’s toxicity. Results in this work show that EPR spectroscopy is a suitable tool for analysis of lipid wraps around nanoparticles. The developed method could become a way of determining harmfulness of nanomaterials.

• Keywords: EPR, nanoparticles, lipid membranes, lipid wraps, spin labels, conformational entropy