R. Stiufiuc

SERS-active silver colloids prepared by reduction of silver nitrate with short-chain polyethylene glycol

We report a fast, one-step, facile, and green preparation method that yields very stable and biocompatible silver colloids that are highly active as surface-enhanced Raman spectroscopy (SERS) platforms that has a possible application in biomedicine. Reduction of silver nitrate has been carried out using polyethylene glycol (PEG) which acts as both reducing agent and stabilizer. It turned out that the -OH groups provided by the addition of NaOH represent a key element in the successful synthesis of PEG-coated silver nanoparticles (AgNPs). The as-obtained silver colloids have been characterized by UV-visible spectroscopy, transmission electron spectroscopy, and SERS using 532- and 633-nm laser lines on a dispersive Raman spectrometer. Several analytes as methylene blue, p-aminothiophenol, amoxicillin, and Cu(PAR)2 were used to prove SERS enhancement of the obtained silver colloid. It has been found that the PEGylated AgNPs provide SERS signals comparable to those achieved using classical hydroxylamine and citrate-reduced silver colloids, thus demonstrating the ability of this new method to prepare biocompatible silver colloids.

Enhanced laser thermal ablation for the in vitro treatment of liver cancer by specific delivery of multiwalled carbon nanotubes functionalized with human serum albumin

The main goal of this investigation was to develop and test a new method of treatment for human hepatocellular carcinoma (HCC). We present a method of carbon nanotube-enhanced laser thermal ablation of HepG2 cells (human hepatocellular liver carcinoma cell line) based on a simple multiwalled carbon nanotube (MWCNT) carrier system, such as human serum albumin (HSA), and demonstrate its selective therapeutic efficacy compared with normal hepatocyte cells. Both HepG2 cells and hepatocytes were treated with HSA–MWCNTs at various concentrations and at various incubation times and further irradiated using a 2 W, 808 nm laser beam. Transmission electron, phase contrast, and confocal microscopy combined with immunochemical staining were used to demonstrate the selective internalization of HSA–MWCNTs via Gp60 receptors and the caveolin-mediated endocytosis inside HepG2 cells. The postirradiation apoptotic rate of HepG2 cells treated with HSA–MWCNTs ranged from 88.24% (for 50 mg/L) at 60 sec to 92.34% (for 50 mg/L) at 30 min. Significantly lower necrotic rates were obtained when human hepatocytes were treated with HSA–MWCNTs in a similar manner. Our results clearly show that HSA–MWCNTs selectively attach on the albondin (aka Gp60) receptor located on the HepG2 membrane, followed by an uptake through a caveolin-dependent endocytosis process. These unique results may represent a major step in liver cancer treatment using nanolocalized thermal ablation by laser heating.

Selective ex-vivo photothermal ablation of human pancreatic cancer with albumin functionalized multiwalled carbon nanotubes

The process of laser-mediated ablation of cancer cells marked with biofunctionalized carbon nanotubes is frequently called “nanophotothermolysis”. We herein present a method of selective nanophotothermolisys of pancreatic cancer (PC) using multiwalled carbon nanotubes (MWCNTs) functionalized with human serum albumin (HSA). With the purpose of testing the therapeutic value of these nanobioconjugates, we have developed an ex-vivo experimental platform. Surgically resected specimens from patients with PC were preserved in a cold medium and kept alive via intra-arterial perfusion. Additionally, the HSA-MWCNTs have been intra-arterially administered in the greater pancreatic artery under ultrasound guidance. Confocal and transmission electron microscopy combined with immunohistochemical staining have confirmed the selective accumulation of HSA-MWCNTs inside the human PC tissue. The external laser irradiation of the specimen has significantly produced extensive necrosis of the malign tissue after the intra-arterial administration of HSA-MWCNTs, without any harmful effects on the surrounding healthy parenchyma. We have obtained a selective photothermal ablation of the malign tissue based on the selective internalization of MWCNTs with HSA cargo inside the pancreatic adenocarcinoma after the ex-vivo intra-arterial perfusion.

Transport limitations and Schottky barrier height in titanium silicide nanowires grown on the Si(111) surface

The authors have performed electrical measurements at variable temperatures on self-assembled titanium silicide nanowires (NWs) grown on a Si(111) surface. The authors find a metallic I(V) characteristic for the NWs at a temperature of 77K, whereas scanning tunneling spectroscopic measurements obtained at temperatures below 25K yield a rectifying behavior. This behavior indicates that the NWs are electronically decoupled from the Si surface on a voltage range of several hundreds of meV at low temperatures. From these measurements, the authors precisely determine the Schottky barrier height between the NWs and the Si surface.

Critical currents of Bi:2212 doped by Fe and Ni

Abstract Measurements of the irreversible magnetization, ac susceptibility and electrical resistivity of Bi 2 Sr 2 Ca 1− x Er x (Cu 1− y M y ) 2 O 8+ d bulk are reported. Low concentrations of the doping elements increase the pinning force density and shift the magnetic irreversibility line towards higher fields. The intergranular critical current density was determined from ac susceptibility data by varying the field amplitude H ac in the range from 0.4 to 1000 A/m and from the irreversible part of magnetization using Bean’s model. The results were discussed in terms of SIS- and SNS-type models for granular superconductors.

The silent healer: miR-205-5p up-regulation inhibits epithelial to mesenchymal transition in colon cancer cells by indirectly up-regulating E-cadherin expression

EMT represents the dominant program within advanced stages of colon cancer, where cells acquire migratory characteristics in order to invade secondary tissues and form metastasis. Where the majority of the therapeutic strategies are concentrated on the reduction of the tumor mass through different apoptotic mechanisms, the present study advocates an important role for miR-205-5p in impairment of colon cancer cells migration and restoration of the epithelial phenotype. Upon identification of a homogenous downregulated profile for miR-205-5p in colon adenocarcinoma patients, functional studies demonstrated that experimental upregulation of this sequence is able to significantly raise the levels of E-cadherin through direct inhibition of ZEB1. Moreover, the elevation in CDH1 expression was translated into functional parameters where cells lost their invasion and migratory characteristics and formed homogenous clusters through adhesion interactions. Survival analysis of colon adenocarcinoma patients revealed that low levels of miR-205-5p are associated with an unfavorable prognostic compared to those with increased expression, demonstrating the possible clinical utility of miR-205-5p replacement. Exogenous administration of miRNA mimics was not associated with significant changes in cell viability or inflammatory pathways. Therefore, the proposed strategy is aiming towards inhibition of metastasis and limitation of the tumor borders in advanced stages patients in order to prolong the survival time and to increase the efficiency of the current therapeutic strategies.

A new class of pegylated plasmonic liposomes: Synthesis and characterization

The multifunctional nanoobjects that can be controlled, manipulated and triggered using external stimuli represent very promising candidates for nanoscale therapeutic and diagnostic applications. In this study we report the successful synthesis and characterization of a new class of very stable multifunctional nanoobjects, containing cationic liposomes decorated with PEGylated gold nanoparticles (PEGAuNPs). The multifunctional hybrid nanoobjects (mHyNp) were prepared by taking advantage of the electrostatic interactions between small unilamelar cationic liposomes and negatively charged gold nanoparticles. The mHyNps have been investigated by UV-VIS absorption spectroscopy, Dynamic Light Scattering (DLS), Zeta Potential Measurements and Transmission Electron Microscopy (TEM). The TEM images clearly revealed the attachment of individual gold nanoparticles onto the spherical outer surface of the cationic liposomes which was also confirmed by DLS and UV-VIS data. Furthermore, the plasmonic properties of the hybrid complexes have been evaluated by using the Surface Enhanced Raman Spectroscopy (SERS) technique. It is shown that PEG mediated interaction between the liposomes and the gold nanoparticles enabled the recording of the SER spectra of the liposomes in aqueous environment, thus demonstrating the plasmonic properties of the hybrids.

Effects of rare earth ion substitution for Ca in (Bi,Pb):2223 superconductors

Abstract The effect of partial replacement of Ca by Y, Er and Lu on the structural transport properties of (Bi 1.6 Pb 0.4 )(Sr 1.8 Ba 0.2 )(Ca 1− x R x ) 2 Cu 3 O y superconductors ceramics (0≤ x ≤0.03) have been investigated. The substitution of Y, Lu and Er at the Ca site induced the decrease of the volume fraction for the 2223 phase and the increase of the 2212 and 2201 phases volume fractions. In the normal state, all the samples are characterized by a linear temperature dependence of electrical resistivity and Hall concentrations. The rate of depression for the critical temperature in x =0.02 samples found to be nearly the same for all of these substitutions. The nature of T C suppression may be attributed to the increase of oxygen content in Bi 2 O 2 double layers with increasing Y, Lu and Er concentrations. The sample shows a linear dependence of intergranular temperature as a function of AC field amplitude, which is in agreement with the Muller critical state model.

Small versus Large Iron Oxide Magnetic Nanoparticles: Hyperthermia and Cell Uptake Properties.

Efficient use of magnetic hyperthermia in clinical cancer treatment requires biocompatible magnetic nanoparticles (MNPs), with improved heating capabilities. Small (~34 nm) and large (~270 nm) Fe3O4-MNPs were synthesized by means of a polyol method in polyethylene-glycol (PEG) and ethylene-glycol (EG), respectively. They were systematically investigated by means of X-ray diffraction, transmission electron microscopy and vibration sample magnetometry. Hyperthermia measurements showed that Specific Absorption Rate (SAR) dependence on the external alternating magnetic field amplitude (up to 65 kA/m, 355 kHz) presented a sigmoidal shape, with remarkable SAR saturation values of ~1400 W/gMNP for the small monocrystalline MNPs and only 400 W/gMNP for the large polycrystalline MNPs, in water. SAR values were slightly reduced in cell culture media, but decreased one order of magnitude in highly viscous PEG1000. Toxicity assays performed on four cell lines revealed almost no toxicity for the small MNPs and a very small level of toxicity for the large MNPs, up to a concentration of 0.2 mg/mL. Cellular uptake experiments revealed that both MNPs penetrated the cells through endocytosis, in a time dependent manner and escaped the endosomes with a faster kinetics for large MNPs. Biodegradation of large MNPs inside cells involved an all-or-nothing mechanism.

SYNTHESIS, MAGNETIC AND TRANSPORT PROPERTIES OF Ru1-xSbxSr2GdCu2O8 COMPOUNDS

Polycrystalline samples with a nominal composition Ru1-xSbxSr2GdCu2O8-d were prepared by a solid state reaction technique. A mixture of RuO2, Sb2O3, Gd2O3, SrCO3 and CuO was used to obtain the samples. We performed X-ray diffraction analyses, DC susceptibility and transport measurements and the studies showed that the samples were almost pure Ru-1212 phase. We also observed that Sb doping reduce the conductivity of the system and the transition temperature decreases with increasing Sb content. This may be due to a distortion of RuO6 octahedral which is responsible for the increase of holes localization.