Adina Coroaba

Theoretical study on β-cyclodextrin inclusion complexes with propiconazole and protonated propiconazole.

Summary The synthesis of the β-cyclodextrin/propiconazole nitrate inclusion complex and the advantages of the encapsulation of this drug were recently reported, but the experimental data only partially revealed the structure of the supramolecular complex due to the limitations in understanding the intermolecular association mechanism. The present work describes the equilibrium molecular geometries of β-cyclodextrin/propiconazole and β-cyclodextrin/protonated propiconazole, established by the AM1 and PM3 semi-empirical methods. The affinity between different parts of the guest molecule and the cyclodextrin cavity was studied considering that propiconazole possesses three residues able to be included into the host cavity through primary or secondary hydroxyl rims. The results have revealed that the most stable complex is formed when the azole residue of the propiconazole enters the cavity of the cyclodextrin through the narrow hydroxyl’s rim.

Hybrid fullerene conjugates as vectors for DNA cell-delivery

The present study reports fullerene conjugates that act as efficient binders of double stranded DNA (dsDNA) into cytofriendly polyplexes. The conjugates are designed to generate dendrimeric structures, having C60 as the core and bearing linear or branched PEI and polyethyleneglycol (PEG) arms (∼2 kDa). Simple and reproducible synthesis pathways provided C60-PEI and C60-PEG-PEI conjugates. They were able to bind linear and plasmidic dsDNA and they form particulate polyplexes of 50 to 200 nm in diameter. The resulted polyplexes toggle between the anionic and cationic state at nitrogen to phosphorous ratios (N/P) of about 5, as revealed by their zeta potential and became colloidally stable at N/P ratios above 10, as determined by atomic force microscopy (AFM). They are electrophoretically unbreakable starting with N/P ratios of 3 and of 5 when salmon sperm DNA and pEYFP-C1 plasmid, respectively are loaded. Both C60-PEI·pEYFP and C60-PEG-PEI·pEYFP polyplexes are non-cytotoxic against HEK 293T cells in culture and exhibit transfection efficiency better than 25% (N/P ratios above 20) and 6% (N/P ratios above 60) respectively, measured by flow cytometry. For comparison, the commercial SuperFect® from Qiagen (positive control) was able to provide an efficiency of 15-20%, under similar conditions. Moreover, the C60-PEG-PEI conjugate is as performant as the positive control in terms of expression of EYFP reporter gene in cultured cells and exhibited high cytocompatibility, determining cell proliferation up to 200%. Our study proved that C60-PEG-PEI is effective vector for DNA delivery being, in addition, easily synthesizable, practically non-cytotoxic and as efficient the commercially available transfection tools.

Functional silsesquioxane-based hierarchical assemblies for antibacterial/antifungal coatings

This paper reports the first study on functional silsesquioxane-based hierarchical assemblies containing an ordered distribution of silver nanoparticles with a large number of {111} facets, obtained through sol-gel reaction, intended for antibacterial/antifungal coatings.

Photoluminescent polymer composites with R, G, B emission and their potential applications in LCD displays

In this work, red, green and blue emitting composites with remarkable photoluminescence properties were obtained through embedding Eu3+, Tb3+ and Y3+ complexes with 2-(1H-1,2,4-triazol-3-yl)pyridine in poly(vinyl alcohol) and poly(n-vinyl pyrrolidone) matrices which were processed in thin or thick films. Interestingly, through embedding in the polymer matrices, their luminescence properties are markedly enhanced compared to the free complexes. PLQY values were enhanced from an average 25–30% to 52–69%, while the emission purity, especially in the case of Eu3+ containing composites, was greatly improved. The prepared composites were investigated through FT-IR analysis while the emphasis on fluorescence spectroscopy provided important details regarding the impact of embedding the complexes in the polymer matrices; luminescence lifetime, absolute PLQY and chromaticity parameters were investigated in detail. The morphology of the composite films was investigated through AFM and SEM. Based on their remarkable photoluminescence properties we are suggesting their implementation in AMLCD displays in a new approach which could replace the RGB colour filters, thus bringing several potential advantages over the current approach. The facile preparation and emission characteristics should be important arguments for their implementation as photonic conversion media in various optoelectronic devices. Other applications like full colour watermarks in special purpose papers could easily take advantage of the prepared composites.

Nail Damage (Severe Onychodystrophy) Induced by Acrylate Glue: Scanning Electron Microscopy and Energy Dispersive X-Ray Investigations

Background: Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques have been used in various fields of medical research, including different pathologies of the nails; however, no studies have focused on obtaining high-resolution microscopic images and elemental analysis of disorders caused by synthetic nails and acrylic adhesives. Methods: Damaged/injured fingernails caused by the use of acrylate glue and synthetic nails were investigated using SEM and EDX methods. Results: SEM and EDX proved that synthetic nails, acrylic glue, and nails damaged by contact with acrylate glue have a different morphology and different composition compared to healthy human nails. Conclusions: SEM and EDX analysis can give useful information about the aspects of topography (surface sample), morphology (shape and size), hardness or reflectivity, and the elemental composition of nails.

Plasma-activated fibrinogen coatings onto poly(vinylidene fluoride) surface for improving biocompatibility with tissues

CO2, N2, and N2/H2 radiofrequency plasma exposure was used for functionalization of poly(vinylidene fluoride) surface aiming the fibrinogen immobilization. Fibrinogen was immobilized onto poly(vinylidene fluoride) surface using both simple plasma activation and covalent coupling. The modified surfaces have been characterized by X-ray photoelectron spectroscopy, attenuated total reflectance–Fourier transform infrared spectroscopy, near infrared–chemical imaging, atomic force microscopy, and wettability measurements, and the obtained materials were tested as supports for fibroblast cell cultures. The plasma type and the immobilization procedure have influenced the fibrinogen attachment onto the poly(vinylidene fluoride) surface, which was achieved mainly through amide bonds when using coupling agents. Covalent immobilization of fibrinogen onto poly(vinylidene fluoride) surface leads to a more stable protein-modified polymer surface. Non-cytotoxic plasma-based coating technology has the ability to covalently immobilize bioactive molecules for surface modification of some biomaterials that mainly could be achieved by the immobilization of proteins such as fibrinogen that triggers desirable cellular responses. The fibrinogen-modified poly(vinylidene fluoride) materials showed increased cell viability of fibroblasts. Cell viability was enhanced by plasma-activated fibrinogen coatings onto poly(vinylidene fluoride) surface, this being more significant if coating was linked further by a coupling reaction. Hence, they could be good candidates for biomedical applications.

Collagen immobilization on ultraviolet light-treated poly(ethylene terephthalate):

The present article is focused on the studies regarding the effects of ultraviolet (UV) light on poly(ethylene terephthalate) (PET) films surfaces using scanning electron microscopy (SEM), Fourier transform infrared, X-ray photoelectron spectrometry (XPS), and atomic force microscopy (AFM) measurements, subsequent to collagen immobilization. UV treatment influences the surface energy of polymers as the result of the polymer chain breaking, followed by insertion of oxygen-containing functional groups. Accordingly, after UV light treatment, collagen was adsorbed on the PET surfaces in different proportions. Significant changes in the surface topography appeared after collagen immobilization on UV-treated PET films, and they were put in evidence by SEM and tapping-mode AFM experiments. XPS measurements demonstrated the adsorption of collagen on PET UV light-altered surfaces by increasing of nitrogen content. The cytocompatibility tests using stem cells have shown good results for all treated polymers.

Erosion as a possible mechanism for the decrease of size of plastic pieces floating in oceans

A sea water wave tank fitted in an artificial UV light weathering chamber was built to study the behaviour of polypropylene (PP) injected pieces in close ocean-like conditions. In air, the same pieces sees a degradation in the bulk with a decrease of mechanical properties, a little change of crystal properties and nearly no change of surface chemistry. Weathering in the sea water wave tank shows only a surface changes, with no effect on crystals or mechanical properties with loss of small pieces of matter in the sub-micron range and a change of surface chemistry. This suggests an erosion dispersion mechanism. Such mechanism could explain why no particle smaller than about one millimeter is found when collecting plastic debris at sea: there are much smaller, eroded from plastic surfaces by a mechano-chemical process similar to the erosion mechanism found in the dispersion of agglomerate under flow.

Superparamagnetic Composites Based on Ionic Resin Beads/CaCO3/Magnetite

The preparation of superparamagnetic composites obtained by CaCO3 mineralization from supersaturate aqueous solutions is presented. The preparation was conducted in the presence of oleic acid stabilized magnetite nanoparticles as a water-based magnetic fluid and insoluble templates as gel-like cross-linked polymeric beads. The presence of the magnetic particles in the composites provides a facile way for external manipulation using a permanent magnet, thus allowing the separation and extraction of magnetically modified materials. Two ion exchangers based on divinylbenzene/ethyl acrylate/acrylonitrile cross-linked copolymer-a cation ion exchanger (CIE) and an amphoteric ion exchanger (AIE)-were used, as well as different addition orders of magnetite and CaCO3 crystals growth precursors. The morphology of the composites was investigated by SEM, the polymorphs content by X-ray diffraction, and the thermal stability by thermogravimetric analysis. Polymer, CaCO3 , and magnetite in the composite particles were shown to be present by energy dispersive X-ray (EDX), XPS, and TEM. The sorption capacity for CuII ions was tested, as compared to samples prepared without magnetite.