Polymer-coated hexagonal upconverting nanoparticles: chemical stability and cytotoxicity.

Large (120 nm) hexagonal NaYF4:Yb, Er nanoparticles (UCNPs) were synthesized by high-temperature coprecipitation method and coated with poly(ethylene glycol)-alendronate (PEG-Ale), poly (N,N-dimethylacrylamide-co-2-aminoethylacrylamide)-alendronate (PDMA-Ale) or poly(methyl vinyl ether-co-maleic acid) (PMVEMA). The colloidal stability of polymer-coated UCNPs in water, PBS and DMEM medium was investigated by dynamic light scattering; UCNP@PMVEMA particles showed the best stability in PBS. Dissolution of the particles in water, PBS, DMEM and artificial lysosomal fluid (ALF) determined by potentiometric measurements showed that all particles were relatively chemically stable in DMEM. The UCNP@Ale-PEG and UCNP@Ale-PDMA particles were the least soluble in water and ALF, while the UCNP@PMVEMA particles were the most chemically stable in PBS. Green fluorescence of FITC-Ale-modified UCNPs was observed inside the cells, demonstrating successful internalization of particles into cells. The highest uptake was observed for neat UCNPs, followed by UCNP@Ale-PDMA and UCNP@PMVEMA. Viability of C6 cells and rat mesenchymal stem cells (rMSCs) growing in the presence of UCNPs was monitored by Alamar Blue assay. Culturing with UCNPs for 24 h did not affect cell viability. Prolonged incubation with particles for 72 h reduced cell viability to 40%-85% depending on the type of coating and nanoparticle concentration. The greatest decrease in cell viability was observed in cells cultured with neat UCNPs and UCNP@PMVEMA particles. Thanks to high upconversion luminescence, high cellular uptake and low toxicity, PDMA-coated hexagonal UCNPs may find future applications in cancer therapy.

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.

PEG-Neridronate-Modified NaYF4:Gd3+,Yb3+,Tm3+/NaGdF4 Core-Shell Upconverting Nanoparticles for Bimodal Magnetic Resonance/Optical Luminescence Imaging.

Upconverting nanoparticles are attracting extensive interest as a multimodal imaging tool. In this work, we report on the synthesis and characterization of gadolinium-enriched upconverting nanoparticles for bimodal magnetic resonance and optical luminescence imaging. NaYF4:Gd3+,Yb3+,Tm3+ core upconverting nanoparticles were obtained by a thermal coprecipitation of lanthanide oleate precursors in the presence of oleic acid as a stabilizer. With the aim of improving the upconversion emission and increasing the amount of Gd3+ ions on the nanoparticle surface, a 2.5 nm NaGdF4 shell was grown by the epitaxial layer-by-layer strategy, resulting in the 26 nm core-shell nanoparticles. Both core and core-shell nanoparticles were coated with poly(ethylene glycol) (PEG)-neridronate (PEG-Ner) to have stable and well-dispersed upconverting nanoparticles in a biological medium. FTIR spectroscopy and thermogravimetric analysis indicated the presence of ∼20 wt % of PEG-Ner on the nanoparticle surface. The addition of inert NaGdF4 shell resulted in a total 26-fold enhancement of the emission under 980 nm excitation and also affected the T 1 and T 2 relaxation times. Both r 1 and r 2 relaxivities of PEG-Ner-modified nanoparticles were much higher compared to those of non-PEGylated particles, thus manifesting their potential as a diagnostic tool for magnetic resonance imaging. Together with the enhanced luminescence efficiency, upconverting nanoparticles might represent an efficient probe for bimodal in vitro and in vivo imaging of cells in regenerative medicine, drug delivery, and/or photodynamic therapy.

Magnetic nanoparticles of Ga-substituted ε-Fe2 O3 for biomedical applications: Magnetic properties, transverse relaxivity, and effects of silica-coated particles on cytoskeletal networks.

Magnetic nanoparticles of ε-Fe1.76 Ga0.24 O3 with the volume-weighted mean size of 17 nm were prepared by thermal treatment of a mesoporous silica template impregnated with metal nitrates and were coated with silica shell of four different thicknesses in the range 6-24 nm. The bare particles exhibited higher magnetization than the undoped compound, 22.4 Am2 kg-1 at 300 K, and were characterized by blocked state with the coercivity of 1.2 T at 300 K, being thus the very opposite of superparamagnetic iron oxides. The relaxometric study of the silica-coated samples at 0.47 T revealed promising properties for MRI, specifically, transverse relaxivity of 89-168 s-1 mmol(f.u.)-1 L depending on the shell thickness was observed. We investigated the effects of the silica-coated nanoparticles on human A549 and MCF-7 cells. Cell viability, proliferation, cell cycle distribution, and the arrangement of actin cytoskeleton were assessed, as well as formation and maturation of focal adhesions. Our study revealed that high concentrations of silica-coated particles with larger shell thicknesses of 16-24 nm interfere with the actin cytoskeletal networks, inducing thus morphological changes. Consequently, the focal adhesion areas were significantly decreased, resulting in impaired cell adhesion.

Can ultrafast single-particle analysis using ICP-MS affect the detection limit? Case study: Silver nanoparticles.

Ultrafast measurement using dwell times below 100 µs down to 10 µs is a relatively new feature of single particle analysis using ICP-MS. In this study, we tested the effect of shorter dwell times on the particle size detection limit (Dd.l.). Decreasing dwell times below 100 µs did not lead to a statistically significant decrease in Dd.l. The particle size detection limit (quadrupole ICP-MS) of silver nanoparticles (NP) was estimated to be approx. 10-11 nm. Ag NPs close to Dd.l. were analysed. The 14-nm NPs showed low detection yield; only 5% of number of NPs estimated from transport efficiency was detected. The 20-nm NPs showed 44% detection yield; only in the case of 30-nm NPs did the number of detected NPs correspond to transport efficiency. It is obvious that near Dd.l. estimates of NP concentrations should be made with great caution.

Peak bordering for ultrafast single particle analysis using ICP-MS.

The characterisation of inorganic nanoparticles (NPs) by single particle inductively coupled plasma mass spectroscopy is possible only if the spectrometer is capable of measurement with high time-signal resolution. The latest generation of spectrometers allow for measurements with dwell times (dt) shorter than the 100 µs gold standard, i.e. as low as 10 µs. The statistical behaviours of signals obtained with dt values of 10, 20, 50, and 100 µs were tested for 40, 60, and 100 nm silver NPs. Very low measured signals (units of counts) led to the occurrence of zero signal values inside the peaks corresponding to individual NPs. The probability of the occurrence of a zero signal inside the peak increased with decreasing dt and decreasing NP size. The standard approach to the bordering of the beginning and end of the peak by one zero signal point failed here and lead to the false detection of a larger number of smaller peaks. For example, in the case of 40 nm NPs a quadruple number of peaks were detected for a dt value of 10 µs compared to the 100 µs dt value; the mean peak width at 10 µs dt was approximately 220 µs, while at 100 µs dt it was 550 µs. The results tended to be less distorted when dt was longer and the NP size was larger. Low dt values also led to a distortion of the peak area distribution. For 40 nm NPs and 10 µs, the most frequent peak area and the width of the peak area distribution were not evaluated due to a non-Gaussian course; 20 µs dt caused (compared to 100 µs) a decrease in the most frequent peak area by approximately 35% (33 counts for 100 µs dt vs. 22 counts for 20 µs dt) and an increase in the width of the peak area distribution by 70% (10 counts for 100 µs dt vs. 17 counts for 20 µs dt). Therefore, new approaches to bordering peaks were tested, which consisted of searching for an uninterrupted zero signal point sequence with a total length of 50 µs or 100 µs. Only the criterion of a 100 µs delay between the two adjacent peaks resulted in values of the number of detected peaks, the most frequent peak areas, and the width of peak area distribution virtually independent of dt.

Manganese-Zinc Ferrites: Safe and Efficient Nanolabels for Cell Imaging and Tracking In Vivo.

Manganese-zinc ferrite nanoparticles were synthesized by using a hydrothermal treatment, coated with silica, and then tested as efficient cellular labels for cell tracking, using magnetic resonance imaging (MRI) in vivo. A toxicity study was performed on rat mesenchymal stem cells and C6 glioblastoma cells. Adverse effects on viability and cell proliferation were observed at the highest concentration (0.55 mM) only; cell viability was not compromised at lower concentrations. Nanoparticle internalization was confirmed by transmission electron microscopy. The particles were found in membranous vesicles inside the cytoplasm. Although the metal content (0.42 pg Fe/cell) was lower compared to commercially available iron oxide nanoparticles, labeled cells reached a comparable relaxation rate R 2, owing to higher nanoparticle relaxivity. Cells from transgenic luciferase-positive rats were used for in vivo experiments. Labeled cells were transplanted into the muscles of non-bioluminescent rats and visualized by MRI. The cells produced a distinct hypointense signal in T2- or T2*-weighted MR images in vivo. Cell viability in vivo was verified by bioluminescence.

The effect of magnetic nanoparticles on neuronal differentiation of induced pluripotent stem cell-derived neural precursors.

INTRODUCTION: Magnetic resonance (MR) imaging is suitable for noninvasive long-term tracking. We labeled human induced pluripotent stem cell-derived neural precursors (iPSC-NPs) with two types of iron-based nanoparticles, silica-coated cobalt zinc ferrite nanoparticles (CZF) and poly-l-lysine-coated iron oxide superparamagnetic nanoparticles (PLL-coated γ-Fe2O3) and studied their effect on proliferation and neuronal differentiation. MATERIALS AND METHODS: We investigated the effect of these two contrast agents on neural precursor cell proliferation and differentiation capability. We further defined the intracellular localization and labeling efficiency and analyzed labeled cells by MR. RESULTS: Cell proliferation was not affected by PLL-coated γ-Fe2O3 but was slowed down in cells labeled with CZF. Labeling efficiency, iron content and relaxation rates measured by MR were lower in cells labeled with CZF when compared to PLL-coated γ-Fe2O3. Cytoplasmic localization of both types of nanoparticles was confirmed by transmission electron microscopy. Flow cytometry and immunocytochemical analysis of specific markers expressed during neuronal differentiation did not show any significant differences between unlabeled cells or cells labeled with both magnetic nanoparticles. CONCLUSION: Our results show that cells labeled with PLL-coated γ-Fe2O3 are suitable for MR detection, did not affect the differentiation potential of iPSC-NPs and are suitable for in vivo cell therapies in experimental models of central nervous system disorders.

Transfer of thallium from rape seed to rape oil is negligible and oil is fit for human consumption.

Rape and other Brassicaceae family plants can accumulate appreciable amounts of thallium from the soil. Because some species of this family are common crops utilised as food for direct consumption or raw materials for food production, thallium can enter the food chain. A useful method for thallium determination is inductively coupled plasma mass spectrometry. The limit of detection (0.2 pg ml(-1) Tl or 0.02 ng g(-1) Tl, taking in the account dilution during sample decomposition) found in the current study was very low, and the method can be used for ultra-trace analysis. Possible transfer of thallium from rape seed to the rape oil was investigated in two ways. The balance of thallium in rape seed meal (content 140-200 ng g(-1) Tl) and defatted rape seed meal indicated that thallium did not pass into the oil (p < 0.05). Moreover, the analyses of thallium in six kinds of edible rape seed oil and three kinds of margarines showed that the amount of thallium in rape seed oil is negligible.

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

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.

A novel sorbent for chromatographic separations: a silica matrix modified with non-covalently bonded tetrakis(ß-cyclodextrin)-porphyrin conjugates.

We prepared new phases for LC that consisted of silica modified with non-covalently bonded tetrakis(ß-cyclodextrin)-porphyrin (where cyclodextrin is CD) conjugates. The effects of the porphyrin core, type of spacer and ß-CD moieties on the behaviours of the modified phases for the separation of aromatic compounds (benzene, toluene, ethylbenzene, propylbenzene, butylbenzene, pentylbenzene, o-terphenyl, triphenylene, phenol and caffeine) and fluorinated aromatic compounds (pentafluorobenzonitrile, pentafluoronitrobenzene and hexafluorobenzene) were studied using the Tanaka test. The results indicate that the non-covalent substitution of silica with CD-based macromolecules that have a porphyrin core can be a very effective method for preparing novel sorbents with specific chromatographic properties for applications in LC.

Application of bare gold nanoparticles in open-tubular CEC separations of polyaromatic hydrocarbons and peptides.

In this study, bare gold nanoparticles (GNPs) immobilized in the sol-gel-pretreated fused-silica (FS) capillary as a stationary phase for open-tubular capillary electrochromatography (OT-CEC) are for the first time shown to be able to separate both hydrophobic polyaromatic hydrocarbons (PAHs) as well as hydrophilic cationic antimicrobial peptides. Model mixture of four PAHs, naphthalene, fluorene, phenanthrene, and anthracene, was resolved by OT-CEC in the GNP-modified FS capillaries using the hydro-organic background electrolyte (BGE) composed of 20 mmol/L sodium phosphate buffer, pH 7, modified with ACN at 8:2 v/v ratio. On the other hand, three synthetic analogues of an antimicrobial peptide mastoparan PDD-B, basic tetradecapeptides INWKKLGKKILGAL-NH(2), INSLKLGKKILGAL-NH(2) and NWLRLGRRILGAL-NH(2), were separated in aqueous acidic BGEs, pH 2.1-3.1, composed of weak acids (formic and acetic) or amphoteric amino or imino acids (aspartic or iminodiacetic), utilizing the advantage of a slow reversed (anodic) EOF and slightly positive charge of the GNP-modified FS capillary suppressing the adsorption of cationic peptides on the inner capillary wall and improving their resolution.

Immobilized metallacarborane as a new type of stationary phase for high performance liquid chromatography.

A new type of high performance liquid chromatography (HPLC) stationary phase was prepared, and its chromatographic properties were evaluated. The sorbent was composed of metallacarborane covalently bound to silica. Because of the chemical structure of the immobilized metallacarborane, the synthesized stationary phase was able to interact with nonpolar analytes via hydrophobic interactions. The chromatographic behavior of several low-molecular-weight hydrocarbons on the sorbent under typical reversed-phase conditions was compared with octadecyl-, sulfo phenyl- and aminopropyl-modified silica stationary phases. Moreover, as a consequence of the synthetic protocol employed, the immobilization of the metallacarborane led to the development of a zwitterionic chemically bonded phase, which demonstrated excellent resistance to "phase collapse" in a 100% aqueous environment. Finally, preliminary experiments indicated that the new stationary phase has the potential for utilization in hydrophilic interaction chromatography (HILIC) mode for the separation of polar compounds.

Guaifenesin enhances the analgesic potency of ibuprofen, nimesulide and celecoxib in mice.

OBJECTIVES: Previously, we found that guaifenesin enhances analgesia induced by paracetamol. The aim of the present study was to determine whether guaifenesin is able to also increase analgesic activity in the non-steroid anti-inflammatory drugs ibuprofen, nimesulide and celecoxib. In addition we investigated the influence of guaifenesin on plasma levels of nimesulide. METHODS: A model of visceral pain consisting of intraperitoneal injection of acetic acid (writhing test) was used. Levels of nimesulide in plasma were measured by HPLC. All drugs were given orally and tested in mice. RESULTS: Guaifenesin alone did not produce any antinociceptive effect. Simultaneous administration of guaifenesin (200 mg/kg) and subanalgesic doses of ibuprofen (10 and 30 mg/kg), nimesulide (10 and 20 mg/kg) or celecoxib (1 and 5 mg/kg) resulted in a significant antinociceptive effects. The plasma levels of nimesulide were significantly higher in combination with guaifenesin at 30, 60 and 90 min after oral administration in comparison to nimesulide monotherapy. CONCLUSION: The present results suggest that guaifenesin might enhance the analgesic activity of various non-steroidal anti-inflammatory drugs.

Extraction of p-hydroxyacetophenone and catechin from Norway spruce needles. Comparison of different extraction solvents.

The phenolic compounds p-hydroxyacetophenone and catechin have been extracted from Norway spruce needles with pure methanol, 80 and 50% (v/v) aqueous methanol, pure acetonitrile, 80% (v/v) aqueous acetonitrile, and pure water. Extraction efficiency of the individual solvents was compared. Although 80% aqueous methanol is the solvent most frequently used for extraction of soluble phenolic compounds from needles, it was found that pure methanol is a more suitable extraction solvent. Surprisingly, a two-step procedure based on the extraction of crushed needles with water then re-extraction with methanol proved a good alternative to direct extraction with methanol. Extraction of uncrushed spruce needles might indicate that relatively more p-hydroxyacetophenone than catechin was located in the surface layer of the needle.