Preparation of uniform superparamagnetic particles with polymer coating for biomedical applications

Aim of this thesis was to design and prepare polymer-coated monodisperse Fe3O4 nanoparticles as a safe and non-toxic contrast agent for magnetic resonance imaging (MRI) and heat mediator for hyperthermia. Uniform superparamagnetic Fe3O4 nanoparticles were synthesized by thermal decomposition of Fe(III) oleate, mandelate, or glucuronate in high- boiling solvents at temperature >285 řC. Size of the particles was controlled in the range of 8- 27 nm by changing reaction parameters, i.e., temperature, type of iron precursor, and concentration of stabilizer (oleic acid and/or oleylamine), while preserving uniformity of the nanoparticles. Because particles contained hydrophobic stabilizer on the surface, they were dispersible only in organic solvents. To ensure water dispersibility, oleic acid on the particle surface was replaced by hydrophilic and biocompatible methoxy-poly(ethylene glycol) (PEG) and poly(3-O-methacryloyl-α-D-glucopyranose) by ligand exchange. Polymers were previously terminated with anchoring-end groups (hydroxamic or phosphonic) to provide firm bonding to iron atoms on the particle surface. Fe3O4 nanoparticles were also hydrophilized by encapsulation into a silica shell by reverse microemulsion method. Tetramethyl orthosilicate was used to prepare Fe3O4@SiO2 nanoparticles, which were..

Příprava uniformních superparamagnetických částic s polymerním povlakem pro biomedicínské aplikace

Cílem této práce bylo navrhnout a připravit polymerem pokryté monodisperzní Fe3O4 nanočástice jako bezpečné a netoxické kontrastní činidlo pro magnetické rezonanční zobrazení a mediátor pro hypertermii. Uniformní superparamagnetické Fe3O4 nanočástice byly syntetizovány teplotním rozkladem oleátu, mandelátu a glukuronátu železitého ve vysokovroucích rozpouštědlech při teplotách >285 řC. Velikost částic byla regulována v rozmezí 8-27 nm změnou reakčních parametrů, např. teplotou, typem organického prekurzoru a koncentrací stabilizátoru (olejové kyseliny a/nebo oleylaminu) tak, aby byla zachována uniformita nanočástic. Částice připravené teplotním rozkladem obsahovaly hydrofobní stabilizátor a byly proto dispergovatelné pouze v organických rozpouštědlech. Aby byly dispergovatelné ve vodě, byla olejová kyselina na poverchu částic nahrazena hydrofilním a biokompatibilním methoxy-poly(ethylenglykolem) (PEG) and poly(3-O- methakryloyl-α-D-glukopyranosou) pomocí metody výměny ligandů. Navázání obou polymerů k atomům železa na povrchu nanočástic bylo dosaženo díky vhodným koncovým skupinám (hydroxamovým nebo fosfonovým). Fe3O4 nanočástice byly také hydrofilizovány enkapsulací do siliky, hydrolýzou tetramethyl ortoxysilikátu, tzv. reverzní mikroemulzní metodou. Takto připravené Fe3O4@SiO2 nanočástice byly...Aim of this thesis was to design and prepare polymer-coated monodisperse Fe3O4 nanoparticles as a safe and non-toxic contrast agent for magnetic resonance imaging (MRI) and heat mediator for hyperthermia. Uniform superparamagnetic Fe3O4 nanoparticles were synthesized by thermal decomposition of Fe(III) oleate, mandelate, or glucuronate in high- boiling solvents at temperature >285 řC. Size of the particles was controlled in the range of 8- 27 nm by changing reaction parameters, i.e., temperature, type of iron precursor, and concentration of stabilizer (oleic acid and/or oleylamine), while preserving uniformity of the nanoparticles. Because particles contained hydrophobic stabilizer on the surface, they were dispersible only in organic solvents. To ensure water dispersibility, oleic acid on the particle surface was replaced by hydrophilic and biocompatible methoxy-poly(ethylene glycol) (PEG) and poly(3-O-methacryloyl-α-D-glucopyranose) by ligand exchange. Polymers were previously terminated with anchoring-end groups (hydroxamic or phosphonic) to provide firm bonding to iron atoms on the particle surface. Fe3O4 nanoparticles were also hydrophilized by encapsulation into a silica shell by reverse microemulsion method. Tetramethyl orthosilicate was used to prepare Fe3O4@SiO2 nanoparticles, which were...Katedra fyzikální a makromol. chemieDepartment of Physical and Macromolecular ChemistryPřírodovědecká fakultaFaculty of Scienc

Silver-Sulfamethazine-Conjugated β-Cyclodextrin/Dextran-Coated Magnetic Nanoparticles for Pathogen Inhibition

In the fight against antibiotic resistance, which is rising to dangerously high levels worldwide, new strategies based on antibiotic-conjugated biocompatible polymers bound to magnetic nanoparticles that allow the drug to be manipulated and delivered to a specific target are being proposed. Here, we report the direct surface engineering of nontoxic iron oxide nanoparticles (IONs) using biocompatible dextran (Dex) covalently linked to β-cyclodextrin (β-CD) with the ability to form non-covalent complexes with silver-sulfamethazine (SMT-Ag). To achieve a good interaction of β-CD-modified dextran with the surface of the nanoparticles, it was functionalized with diphosphonic acid (DPA) that provides strong binding to Fe atoms. The synthesized polymers and nanoparticles were characterized by various methods, such as nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) and ultraviolet–visible (UV–Vis) spectroscopies, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), atomic absorption spectroscopy (AAS), dynamic light scattering (DLS), etc. The resulting magnetic ION@DPA-Dex-β-CD-SMT-Ag nanoparticles were colloidally stable in water and contained 24 μg of antibiotic per mg of the particles. When tested for in vitro antimicrobial activity on Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria and fungi (yeast Candida albicans and mold Aspergillus niger), the particles showed promising potential

Cationic Polymer-Coated Magnetic Nanoparticles with Antibacterial Properties: Synthesis and In Vitro Characterization

Uniformly sized magnetite nanoparticles (Dn = 16 nm) were prepared by a thermal decomposition of Fe(III) oleate in octadec-1-ene and stabilized by oleic acid. The particles were coated with Sipomer PAM-200 containing both phosphate and methacrylic groups available for the attachment to the iron oxide and at the same time enabling (co)polymerization of 2-(dimethylamino)ethyl methacrylate and/or 2-tert-butylaminoethyl methacrylate at two molar ratios. The poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) and poly[2-(dimethylamino)ethyl methacrylate-co-2-tert-butylaminoethyl methacrylate] [P(DMAEMA-TBAEMA)] polymers and the particles were characterized by 1H NMR spectroscopy, size-exclusion chromatography, transmission electron microscopy, dynamic light scattering, thermogravimetric analysis, magnetometry, and ATR FTIR and atomic absorption spectroscopy. The antimicrobial effect of cationic polymer-coated magnetite nanoparticles tested on both Escherichia coli and Staphylococcus aureus bacteria was found to be time- and dose-responsive. The P(DMAEMA-TBAEMA)-coated magnetite particles possessed superior biocidal properties compared to those of P(DMAEMA)-coated one

Silver nanoparticles in the thermal silver plating of aluminium busbar joints

Thermal silver plating method by means of nanosilver-based paint could be an alternative to electrochemical processes. Electrochemical silver layering on aluminium is typically achieved with an intermediate layer, which provides very good adhesion of the layer to the aluminium surface but increases the resistance of the whole junction system. In the method of silver plating promoted by the authors, the intermediate layer is eliminated. The layer of silver paint was applied directly on the aluminium surface by spraying using aerograph. Procured silver layers, according to ISO 2409, prove proper adhesion to aluminium. The value of contact resistance with a pressure of 300 N cm−2 and current load of 200 A is 0.03 μΩ mm−2, which is comparable to the contact resistance of layers generated by electrochemical means. This new method decreases the level of toxic waste emission and therefore is less harmful for the natural environment. It is also cheaper and simpler than the electrochemical process. An additional advantage is the possibility of silver plating of the chosen surfaces with various shapes

Chemical and Colloidal Stability of Polymer-Coated NaYF₄:Yb,Er Nanoparticles in Aqueous Media and Viability of Cells: The Effect of a Protective Coating

Upconverting nanoparticles (UCNPs) are of particular interest in nanomedicine for in vivo deep-tissue optical cancer bioimaging due to their efficient cellular uptake dependent on polymer coating. In this study, particles, ca. 25 nm in diameter, were prepared by a high-temperature coprecipitation of lanthanide chlorides. To ensure optimal dispersion of UCNPs in aqueous milieu, they were coated with three different polymers containing reactive groups, i.e., poly(ethylene glycol)-alendronate (PEG-Ale), poly(N,N-dimethylacrylamide-co-2-aminoethylacrylamide)-alendronate (PDMA-Ale), and poly(methyl vinyl ether-co-maleic acid) (PMVEMA). All the particles were characterized by TEM, DLS, FTIR, and spectrofluorometer to determine the morphology, hydrodynamic size and ξ-potential, composition, and upconversion luminescence. The degradability/dissolution of UCNPs in water, PBS, DMEM, or artificial lysosomal fluid (ALF) was evaluated using an ion-selective electrochemical method and UV-Vis spectroscopy. The dissolution that was more pronounced in PBS at elevated temperatures was decelerated by polymer coatings. The dissolution in DMEM was relatively small, but much more pronounced in ALF. PMVEMA with multiple anchoring groups provided better protection against particle dissolution in PBS than PEG-Ale and PDMA-Ale polymers containing only one reactive group. However, the cytotoxicity of the particles depended not only on their ability to rapidly degrade, but also on the type of coating. According to MTT, neat UCNPs and UCNP@PMVEMA were toxic for both rat cells (C6) and rat mesenchymal stem cells (rMSCs), which was in contrast to the UCNP@Ale-PDMA particles that were biocompatible. On the other hand, both the cytotoxicity and uptake of the UCNP@Ale-PEG particles by C6 and rMSCs were low, according to MTT assay and ICP-MS, respectively. This was confirmed by a confocal microscopy, where the neat UCNPs were preferentially internalized by both cell types, followed by the UCNP@PMVEMA, UCNP@Ale-PDMA, and UCNP@Ale-PEG particles. This study provides guidance for the selection of a suitable nanoparticle coating with respect to future biomedical applications where specific behaviors (extracellular deposition vs. cell internalization) are expected

Superparamagnetic Fe₃O₄ Nanoparticles: Synthesis by Thermal Decomposition of Iron(III) Glucuronate and Application in Magnetic Resonance Imaging

Monodisperse superparamagnetic Fe₃O₄ nanoparticles coated with oleic acid were prepared by thermal decomposition of Fe­(III) glucuronate. The shape, size, and particle size distribution were controlled by varying the reaction parameters, such as the reaction temperature, concentration of the stabilizer, and type of high-boiling-point solvents. Magnetite particles were characterized by transmission electron microscopy (TEM), as well as electron diffraction (SAED), X-ray diffraction (XRD), dynamic light scattering (DLS), and magnetometer measurements. The particle coating was analyzed by atomic absorption spectroscopy (AAS) and attenuated total reflection (ATR) Fourier transform infrared spectroscopy (FTIR) spectroscopy. To make the Fe₃O₄ nanoparticles dispersible in water, the particle surface was modified with α-carboxyl-ω-bis­(ethane-2,1-diyl)­phosphonic acid-terminated poly­(3-<i>O</i>-methacryloyl-α-<i>D</i>-glucopyranose) (PMG–P). For future practical biomedical applications, nontoxicity plays a key role, and the PMG–P&Fe₃O₄ nanoparticles were tested on rat mesenchymal stem cells to determine the particle toxicity and their ability to label the cells. MR relaxometry confirmed that the PMG–P&Fe₃O₄ nanoparticles had high relaxivity but rather low cellular uptake. Nevertheless, the labeled cells still provided visible contrast enhancement in the magnetic resonance image. In addition, the cell viability was not compromised by the nanoparticles. Therefore, the PMG–P&Fe₃O₄ nanoparticles have the potential to be used in biomedical applications, especially as contrast agents for magnetic resonance imaging