Polytetrafluorethylene-Au as a substrate for surface-enhanced Raman spectroscopy

This study deals with preparation of substrates suitable for surface-enhanced Raman spectroscopy (SERS) applications by sputtering deposition of gold layer on the polytetrafluorethylene (PTFE) foil. Time of sputtering was investigated with respect to the surface properties. The ability of PTFE-Au substrates to enhance Raman signals was investigated by immobilization of biphenyl-4,4'-dithiol (BFD) from the solutions with various concentrations. BFD was also used for preparation of sandwich structures with Au or Ag nanoparticles by two different procedures. Results showed that PTFE can be used for fabrication of SERS active substrate with easy handle properties at low cost. This substrate was sufficient for the measurement of SERS spectrum of BFD even at 10-8 mol/l concentration

"Soft and rigid" dithiols and Au nanoparticles grafting on plasma-treated polyethyleneterephthalate

Surface of polyethyleneterephthalate (PET) was modified by plasma discharge and subsequently grafted with dithiols (1, 2-ethanedithiol (ED) or 4, 4'-biphenyldithiol) to create the thiol (-SH) groups on polymer surface. This "short" dithiols are expected to be fixed via one of -SH groups to radicals created by the plasma treatment on the PET surface. "Free" -SH groups are allowed to interact with Au nanoparticles. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and electrokinetic analysis (EA, zeta potential) were used for the characterization of surface chemistry of the modified PET. Surface morphology and roughness of the modified PET were studied by atomic force microscopy (AFM). The results from XPS, FTIR, EA and AFM show that the Au nanoparticles are grafted on the modified surface only in the case of biphenyldithiol pretreatment. The possible explanation is that the "flexible" molecule of ethanedithiol is bounded to the activated PET surface with both -SH groups. On the contrary, the "rigid" molecule of biphenyldithiol is bounded via only one -SH group to the modified PET surface and the second one remains "free" for the consecutive chemical reaction with Au nanoparticle. The gold nanoparticles are distributed relatively homogenously over the polymer surface

Annealing of gold nanostructures sputtered on polytetrafluoroethylene

Gold nanolayers sputtered on polytetrafluoroethylene (PTFE) surface and their changes induced by post-deposition annealing at 100°C to 300°C are studied. Changes in surface morphology and roughness are examined by atomic force microscopy, electrical sheet resistance by two point technique, zeta potential by electrokinetic analysis and chemical composition by X-ray photoelectron spectroscopy (XPS) in dependence on the gold layer thickness. Transition from discontinuous to continuous gold coverage takes place at the layer thicknesses 10 to 15 nm and this threshold remains practically unchanged after the annealing at the temperatures below 200°C. The annealing at 300°C, however, leads to significant rearrangement of the gold layer and the transition threshold increases to 70 nm. Significant carbon contamination and the presence of oxidized structures on gold-coated samples are observed in XPS spectra. Gold coating leads to a decrease in the sample surface roughness. Annealing at 300°C of pristine PTFE and gold-coated PTFE results in significant increase of the sample surface roughness

Measurement of insulation and dielectric properties of water.

Tato bakalářská práce se zabývá dielektrickými a izolačními vlastnostmi vody. Popisuje strukturu vody, její vodíkové vazby. Vysvětluje základní fyzikální a chemické vlastnosti vody, přičemž popisuje parametry vody jako je dynamická viskozita, vodivost, povrchové napětí, ztrátový činitel, polarizace. Součástí práce je praktická část, která se zabývá měření jednotlivých vod a zobrazuje základní závislosti jako např. závislost kapacity na frekvenci nebo ztrátového činitele na frekvenci.This bachelor thesis deals about dielectric and insulation properties of water. It describes the structure of water, hydrogen bonds. It explains primary physical and chemical properties of water and then it describes parameters of water such as dynamic viscosity, conductivity, surface pension, loss factor, polarization. Part of the work is practical section, which deals measurements of water and shows primary dependence such as capacity dependence on frequency or loss factor on frequency.

Using ferromagnetic nanoparticles with low Curie temperature for magnetic resonance imaging-guided thermoablation

Vít Herynek,1 Karolína Turnovcová,2 Pavel Veverka,3 Tereza Dědourková,4,5 Pavel Žvátora,6 Pavla Jendelová,2 Andrea Gálisová,1 Lucie Kosinová,7 Klára Jiráková,2 Eva Syková2 1MR-Unit, Radiodiagnostic and Interventional Radiology Department, Institute for Clinical and Experimental Medicine, Prague, 2Department of Neuroscience, Institute of Experimental Medicine, 3Department of Magnetics and Superconductors, Institute of Physics, Czech Academy of Sciences, Prague, 4Department of Inorganic Technology, Faculty of Chemical Technology, University of Pardubice, 5SYNPO, akciová společnost, Pardubice, 6Department of Analytical Chemistry, Institute of Chemical Technology, 7Diabetes Center, Institute for Clinical and Experimental Medicine, Prague, Czech Republic Introduction: Magnetic nanoparticles (NPs) represent a tool for use in magnetic resonance imaging (MRI)-guided thermoablation of tumors using an external high-frequency (HF) magnetic field. To avoid local overheating, perovskite NPs with a lower Curie temperature (Tc) were proposed for use in thermotherapy. However, deposited power decreases when approaching the Curie temperature and consequently may not be sufficient for effective ablation. The goal of the study was to test this hypothesis. Methods: Perovskite NPs (Tc =66°C–74°C) were characterized and tested both in vitro and in vivo. In vitro, the cells suspended with NPs were exposed to a HF magnetic field together with control samples. In vivo, a NP suspension was injected into a induced tumor in rats. Distribution was checked by MRI and the rats were exposed to a HF field together with control animals. Apoptosis in the tissue was evaluated. Results and discussion: In vitro, the high concentration of suspended NPs caused an increase of the temperature in the cell sample, leading to cell death. In vivo, MRI confirmed distribution of the NPs in the tumor. The temperature in the tumor with injected NPs did not increase substantially in comparison with animals without particles during HF exposure. We proved that the deposited power from the NPs is too small and that thermoregulation of the animal is sufficient to conduct the heat away. Histology did not detect substantially higher apoptosis in NP-treated animals after ablation. Conclusion: Magnetic particles with low Tc can be tracked in vivo by MRI and heated by a HF field. The particles are capable of inducing cell apoptosis in suspensions in vitro at high concentrations only. However, their effect in the case of extracellular deposition in vivo is questionable due to low deposited power and active thermoregulation of the tissue. Keywords: perovskite nanoparticles, hyperthermia, high-frequency magnetic field, MRI, tumor ablatio

Využití feromagnetických nanočástic s nízkou Curieovou teplotou pro zobrazovací magnetickou rezonancí řízenou termoablaci

Magnetic nanoparticles represent a tool for use in magnetic resonance imaging (MRI)-guided thermoablation of tumors using an external high-frequency mag¬netic field. To avoid local overheating, perovskite nanoparticles with a lower Curie temperature (Tc) were proposed for use in thermotherapy. However, deposited power decreases when approaching the Curie temperature and consequently may not be sufficient for effective ablation. The goal of the study was to test this hypothesis. Perovskite nanoparticles (Tc = 66–74°C) were characterized and tested both in vitro and in vivo. Magnetic particles with low Tc can be tracked in vivo by MRI and heated by a HF field. The particles are capable of inducing cell apoptosis in suspensions in vitro at high concentrations only.Magnetické nanočástice představují nástroj pro použití v magnetickou rezonancí (MRI) řízené termoablaci nádorů pomocí externího vysokofrekvenčního magnetického pole. Aby se zabránilo lokálnímu přehřátí, byly navrženy perovskitové nanočástice s nižší Curieovou teplotou (Tc) pro použití v termoterapii. Nicméně vložená energie se snižuje, když se blíží Curieova teplota a v důsledku toho nemusí být dostatečná pro účinnou ablaci. Cílem této studie bylo otestovat tuto hypotézu. Perovskitové nanočástice (Tc = 66–74 °C) byly charakterizovány a testovány jak in vitro, tak in vivo. Magnetické částice s nízkou Tc mohou být sledovány in vivo pomocí MRI a zahřívány VF polem. Tyto částice jsou schopné indukovat apoptózu buněk v suspenzi in vitro při pouze vysokých koncentracích

The impact of silica encapsulated cobalt zinc ferrite nanoparticles on DNA, lipids and proteins of rat bone marrow mesenchymal stem cells

Nanomateriály jsou v současnosti předmětem intenzivního výzkumu díky jejich možnému využití na poli biomedicíny, optiky a elektroniky. Připravili jsme a testovali nanočástice na bázi feritů s kobaltem a zinkem (Co0.5Zn0.5Fe2O4+γ [CZF-NPs]) obalované amorfní silikou, které by měly sloužit jako kontrastní látka pro sledování transplantovaných buněk v organismu pomocí magnetické rezonance (MRI). Potkaní mesenchymální buňky (rMSC) byly inkubovány 48 h s nízkou, střední nebo vysokou koncentrací (0,05, 0,11 nebo 0,55 mmol) nanočástic nebo se silikou (Si-NPs, 0,11 mmol) sloužící jako negativní kontrola. Internalizace nanočástic byla potvrzena pomocí elektronové transmisní mikroskopie. Biologické účinky byly hodnoceny ihned po expozici a po dalších 72 h v čerstvém médiu bez nanočástic. Pomocí značení annexinem V/PI nebyl odhalen žádný rozdíl v cytotoxicitě (v úmrtnosti buněk, pozn. překl.) mezi jednotlivými skupinami buněk, pouze nejvyšší koncentrace nanočástic snížila přírůstek buněk a zvýšila poškození DNA, které se projevilo jako vyšší počet zlomů a oxidovaných bází. U těchto buněk bylo nalezeno také zvýšení koncentrace 15-F2t-isoprostanu a karbonylových skupin, což svědčilo pro oxidativní poškození u tohoto vzorku. Žádné poškození (makromolekul) nebylo pozorováno u nízké koncentrace nanočástic. I buňky inkubované s touto nejnižší koncentrací nanočástic prokázaly dostatečné relaxační časy v opakovaných MRI experimentech a ICP-MS potvrdila dostatečné množství nanočástic uvnitř buněk. Tyto výsledky podporují možné využití silikou obalovaných CZF-NPs v nízkých netoxických koncentracích jako intracelulární kontrastní látky pro MRI.Nanomaterials are currently the subject of intense research due to their wide variety of potential applications in the biomedical, optical and electronic fields. We prepared and tested cobalt zinc ferrite nanoparticles (Co0.5Zn0.5Fe2O4+γ [CZF-NPs]) encapsulated by amorphous silica in order to find a safe contrast agent and magnetic label for tracking transplanted cells within an organism using magnetic resonance imaging (MRI). Rat mesenchymal stem cells (rMSCs) were labeled for 48 h with a low, medium or high dose of CZF-NPs (0.05; 0.11 or 0.55 mM); silica NPs (Si-NPs; 0.11 mM) served as a positive control. The internalization of NPs into cells was verified by transmission electron microscopy. Biological effects were analyzed at the end of exposure and after an additional 72 h of cell growth without NPs. Compared to untreated cells, Annexin V/Propidium Iodide labeling revealed no significant cytotoxicity for any group of treated cells and only a high dose of CZF-NPs slowed down cell proliferation and induced DNA damage, manifested as a significant increase of DNA-strand breaks and oxidized DNA bases. This was accompanied by high concentrations of 15- F2t-isoprostane and carbonyl groups, demonstrating oxidative injury to lipids and proteins, respectively. No harmful effects were detected in cells exposed to the low dose of CZF-NPs. Nevertheless, the labeled cells still exhibited an adequate relaxation rate for MRI in repeated experiments and ICP-MS confirmed sufficient magnetic label concentrations inside the cells. The results suggest that the silica-coated CZF-NPs, when applied at a non-toxic dose, represent a promising contrast agent for cell labeling