16 research outputs found
Hydrophobically coated superparamagnetic iron oxides nanoparticles incorporated into polymer-based nanocapsules dispersed in water
This paper reports the characterization of iron oxide magnetic nanoparticles obtained via the thermal decomposition of an organometallic precursor, which were then loaded into nanocapsules prepared via the emulsification process in the presence of an amphiphilic derivative of chitosan. The applied synthetic method led to the formation of a hydrophobic layer on the surface of nanoparticles that enabled their loading in the hydrophobic liquid inside of the polymer-based capsules. The average diameter of nanoparticles was determined to be equal to 15 nm, and they were thoroughly characterized using X-ray diffraction (XRD), magnetometry, and Mössbauer spectroscopy. A core–shell structure consisting of a wüstite core and maghemite-like shell was revealed, resulting in an exchange bias effect and a considerable magnetocrystalline anisotropy at low temperatures and a superparamagnetic behavior at room temperature. Importantly, superparamagnetic behavior was observed for the aqueous dispersion of the nanocapsules loaded with the superparamagnetic nanoparticles, and the dispersion was shown to be very stable (at least 48 weeks). The results were analyzed and discussed with respect to the potential future applications of these nanoparticles and nanocapsules based on biopolymers as platforms designed for the magnetically navigated transport of encapsulated hydrophobic substances
dual-modal MRI contrast agents based on superparamagnetic iron oxide nanoparticles with surface attached gadolinium complexes
Dual-mode MRI contrast agents consisting
of superparamagnetic iron oxide nanoparticle (SPION)
cores and gadolinium ions associated with the ionic
chitosan protecting layer were synthesized and studied.
Gadolinium ions were introduced into the coating layer
via direct complex formation on the nanoparticles
surface, covalent attachment or electrostatically driven
deposition of the preformed Gd complex. The modified
SPIONs having hydrodynamic diameters ca. 100 nm
form stable, well-defined dispersions in water and have
excellent magnetic properties. Physiochemical prop-
erties of those new materials were characterized using
e.g., FTIR spectroscopy, dynamic light scattering, X-ray fluorescence, TEM, and vibrating sample mag-
netometry. They behave as superparamagnetics and
shorten both T
1
and T
2
proton relaxation times, thus
influencing both r
1
and r
2
relaxivity values that reach
53.7 and 375.5 mM
-
1
s
-
1
, respectively, at 15 MHz.
The obtained materials can be considered as highly
effective contrast agents for low-field MRI, particu-
larly useful at permanent magnet-based scanners
Dynamics of superparamagnetic iron oxide nanoparticles with various polymeric coatings
In this article, the results of a study of the magnetic dynamics of superparamagnetic iron oxide nanoparticles (SPIONs) with chitosan and polyethylene glycol (PEG) coatings are reported. The materials were prepared by the co-precipitation method and characterized by X-ray diffraction, dynamic light scattering and scanning transmission electron microscopy. It was shown that the cores contain maghemite, and their hydrodynamic diameters vary from 49 nm for PEG-coated to 200 nm for chitosan-coated particles. The magnetic dynamics of the nanoparticles in terms of the function of temperature was studied with magnetic susceptometry and Mössbauer spectroscopy. Their superparamagnetic fluctuations frequencies, determined from the fits of Mössbauer spectra, range from tens to hundreds of megahertz at room temperature and mostly decrease in the applied magnetic field. For water suspensions of nanoparticles, maxima are observed in the absorption part of magnetic susceptibility and they shift to higher temperatures with increasing excitation frequency. A step-like decrease of the susceptibility occurs at freezing, and from that, the Brown’s and Néel’s contributions are extracted and compared for nanoparticles differing in core sizes and types of coating. The results are analyzed and discussed with respect to the tailoring of the dynamic properties of these nanoparticle materials for requirements related to the characteristic frequency ranges of MRI and electromagnetic field hyperthermia
Carbon Dots/Iron Oxide Nanoparticles with Tuneable Composition and Properties
We present a simple strategy to generate a family of carbon dots/iron oxide nanoparticles (C/Fe-NPs) that relies on the thermal decomposition of iron (III) acetylacetonate in the presence of a highly fluorescent carbon-rich precursor (derived via thermal treatment of ethanolamine and citric acid at 180 °C), while polyethylene glycol serves as the passivation agent. By varying the molar ratio of the reactants, a series of C/Fe-NPs have been synthesized with tuneable elemental composition in terms of C, H, O, N and Fe. The quantum yield is enhanced from 6 to 9% as the carbon content increases from 27 to 36 wt%, while the room temperature saturation magnetization is improved from 4.1 to 17.7 emu/g as the iron content is enriched from 17 to 31 wt%. In addition, the C/Fe-NPs show excellent antimicrobial properties, minimal cytotoxicity and demonstrate promising bioimaging capabilities, thus showing great potential for the development of advanced diagnostic tools
Budżetowanie działalności jednostek gospodarczych Teoria i praktyka. Część V
Z wprowadzenia: "Przekazujemy do rąk Czytelników część monografii dotyczącej budżetowania
jednostek gospodarczych. Jej przygotowanie zbiegło się z ukazaniem się manifestu
Precz z budżetami Jeremiego Норе’а i Robina Frasera. Autorzy poddają
tam ostrej krytyce dotychczasowe praktyki stosowania budżetowania kosztowego.
Stąd niniejsza publikacja - między innymi - dlatego różni się istotnie od poprzednich.
Od pewnego czasu - także w Polsce - pojawiały się głosy wskazujące na istotne
niedoskonałości budżetowania kosztowego, na przykład J. Gierusz [Materiały
konferencyjne 2001], G. H. Świderska [Rachunkowośćzarządcza i rachunek kosztów,
2002]. Nie odnosiły one jednak skutku. Nie zauważono też dotąd narastającej
listy zarzutów wytaczanych przeciw finansowym jednostkom miary stosowanym
w budżetowaniu kosztowym, na przykład G. K. Świderska [jak wyżej],
M. Sierpińska, B. Niedbała [Controllingoperacyjny wpnedsiębiorstwie, 2003]. Bez
echa pozostało postawione przez autora pytanie: „zmierzch czy rozwój budżetowania?”
[„Controlling i rachunkowość zarządcza” 9/2002], gdzie jednoznacznie
wskazano, że budżetowanie kosztowe obejmuje jedynie jedną sferę działalności
przedsiębiorstwa i tym samym nie może stanowić wystarczającej podstawy do
sterowania przedsiębiorstwem. Zwolennicy budżetowania kosztowego nawet zgadzali
się ze stawianymi zarzutami, jednak nie reagowali na propozycje zmian
w filozofii i metodologii budżetowania."(...
Specific binding of novel SPION-based system bearing anti-N-cadherin antibodies to prostate tumor cells
PURPOSE: Epithelial–mesenchymal (EMT) transition plays an important role in metastasis and is accompanied by an upregulation of N-cadherin expression. A new nanoparticulate system (SPION/CCh/N-cad) based on superparamagnetic iron oxide nanoparticles, stabilized with a cationic derivative of chitosan and surface-modified with anti-N-cadherin antibody, was synthetized for the effective capture of N-cadherin expressing circulating tumor cells (CTC). METHODS: The morphology, physicochemical, and magnetic properties of the system were evaluated using dynamic light scattering (DLS), fluorescence spectroscopy, Mössbauer spectroscopy, magnetometry, and fluorescence spectroscopy. Atomic force microscopy (AFM), confocal microscopy and flow cytometry were used to study the interaction of our nanoparticulate system with N-cadherin expressed in prostate cancer cell lines (PC-3 and DU 145). A purpose-built cuvette was used in the cancer cell capture experiments. RESULTS: The obtained nanoparticles were a spherical, stable colloid, and exhibited excellent magnetic properties. Biological experiments confirmed that the novel SPION/CCh/N-cad system interacts specifically with N-cadherin present on the cell surface. Preliminary studies on the magnetic capture of PC-3 cells using the obtained nanoparticles were successful. Incubation times as short as 1 minute were sufficient for the synthesized system to effectively bind to the PC-3 cells. CONCLUSION: Results obtained for our system suggest a possibility of using it to capture CTC in the flow conditions
Magnetic properties of collagen-chitosan hybrid materials with immobilized superparamagnetic iron oxide nanoparticles (SPIONs)
The paper presents results of our studies on hybrid materials based on polymers of natural origin containing superparamagnetic iron oxide nanoparticles (SPIONs). Such nanoparticles, coated with the chitosan derivative, were immobilized in a chitosan-collagen hydrogel matrix by crosslinking with genipin. Three types of biopolymer matrices of different collagen-to-chitosan ratios were studied. A thorough magnetic characterization was performed, including magnetic susceptibility, magnetization, and hysteresis loop measurements in a temperature range of 4 K to 300 K and a magnetic field induction up to 8 Tesla. The effect of SPION immobilization and material composition on the magnetic properties of the hybrids was investigated. The results showed that hybrid materials with covalently bounded SPIONs preserved the superparamagnetic character of SPIONs and exhibited promising magnetic properties, which are important for their potential applications
Magnetically navigated core-shell polymer capsules as nanoreactors loadable at the oil/water interface
Polymer
core–shell nanocapsules with magnetic nanoparticles embedded
in their oil cores were fabricated and applied as nano(photo)reactors.
Superparamagnetic iron oxide nanoparticles (SPIONs) coated with oleic
acid were first synthesized and characterized structurally, and their
magnetic properties were determined. The capsules with chitosan-based
shells were then formed in a one-step process by sonication-assisted
mixing of (1) an aqueous solution of the hydrophobically derived chitosan
and (2) oleic acid containing the dispersed SPIONs. In this way, magnetic
capsules with a diameter of approximately 500–600 nm containing
encapsulated SPIONs with an average diameter of approximately 20–30
nm were formed as revealed by dynamic light scattering and scanning
transmission electron microscopy measurements. The composition and
magnetic properties of the formed capsules were also followed using
dynamic light scattering, electron microscopies, and magnetic force
microscopy. The water-dispersible capsules, thanks to their magnetic
properties, were then navigated in a static magnetic field gradient
and transferred between the water and oil phases, as evidenced by
fluorescence microscopy. In this way, the capsules could be loaded
in a controlled way with a hydrophobic reactant, perylene, which was
later photooxidized upon transferring the capsules to the aqueous
phase. The capsules were shown to serve as robust reloadable nanoreactors/nanocontainers
that via magnetic navigation can be transferred between immiscible
phases without disruption. These features make them promising reusable
systems not only for loading and carrying lipophilic actives, conducting
useful reactions in the confined environment of the capsules, but
also for magnetically separating and guiding the encapsulated active
molecules to the site of action