S. Simon

Babeş-Bolyai University, Klausenburg, Cluj, Romania

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Publications (184)252.63 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: In order to improve the physicochemical properties and solubility of the nutraceutical compound Myricetin, we investigated its propensity to form co-crystals with acetamide. A novel co-crystal was obtained by solvent drop grinding of Myricetin and acetamide. The co-crystal formation was evidenced by X-ray powder diffraction, thermal analysis and spectroscopic techniques (FT-IR, 1H MAS NMR). Stability study on exposure to elevated temperature and relative high humidity indicated that the co-crystal change to Myricetin form within 8 weeks. On the other hand, solubility and dissolution measurements showed a 4 times increase in the dissolution rate of the co-crystal in water compared to Myricetin. Our study shows that the co-crystal of Myricetin with acetamide could be a candidate for developing solid oral dosage formulations of enhanced bioavailability.
    No preview · Article · Nov 2015 · Composites Part B Engineering
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    ABSTRACT: 29Si MAS NMR spectroscopic data obtained for heavy metal SiO2–Bi2O3 glasses and partially crystallized samples of similar composition were used to investigate the changes induced in their local structure as the ratio between Bi3 + and Si4 + cations decreases from 18:1 to 6:7. Progressive increase of SiO2/Bi2O3 ratio contributes to the structural relaxation of vitreous network and enhances the glass stability. In glass samples with high silica content the increasing number of Si–O–Si bridges proves the three-dimensional polymerization of silicate network. The shape of NMR signals for glass–ceramic samples depends on the crystalline phases formed for different SiO2/Bi2O3 ratios. The crystalline phases developed by heat treatment of vitreous matrices were identified by X-ray diffraction as Bi12SiO20, Bi5.6Si0.5O9.4 and Bi2SiO5. Scanning electron microscopy analysis was used to examine the morphology of the crystals developed in the glassy silica rich matrices.
    Full-text · Article · Oct 2015 · Journal of Non-Crystalline Solids

  • No preview · Article · Oct 2015 · Journal of Obstetrics and Gynaecology
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    ABSTRACT: Abstract Bioactive glasses of the CaO-SiO2-P2O5 system were synthesized through a sol-gel template method using polyethylene-glycol (PEG) with different molar weights. The samples were investigated by differential thermal analysis, X-ray diffraction and Fourier transform infrared spectroscopy. Electron paramagnetic resonance spectroscopy was employed to evidence possible structural defects and to reveal the response of the investigated glasses to gamma irradiation, and related effects on protein adsorption and samples bioactivity. PEG addition during samples synthesis induces structural changes within the glass matrix, which are dependent on PEG molar weights. At the same time, the use of PEG favors the occurrence of network defects. For the samples prepared with PEG of increased molar weight a lower apatite-forming ability was evidenced by the test carried out in simulated body fluid. It was also demonstrated that the network defects of samples affect the secondary structure of the protein adsorbed on the glass surfaces
    Full-text · Article · Oct 2015 · Ceramics International
  • M. Todea · R.V.F. Turcu · B. Frentiu · S. Simon
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    ABSTRACT: 70SiO2·30Al2O3 and 70SiO2·20Al2O3·10Y2O3 aluminosilicate microparticles with potential biomedical applications were investigated with respect to composition effect on structure and bioactivity tested in vitro, as response to simulated body fluid. The local structure of the samples was evaluated by Fourier transform infrared (FT-IR) and magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. The results indicate that the addition of yttrium to aluminosilicate microspheres influences the surface properties and induces an enhanced bioactivity.
    No preview · Article · Oct 2015 · Journal of Non-Crystalline Solids
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    ABSTRACT: Nanoencapsulation of pharmaceutically active natural compounds into porous systems through sol–gel method leads to new drug delivery materials with sustained release behaviour of the entrapped pharmaceuticals. Properties of inorganic sol–gel-derived silica microparticles loaded with cotton (Gossypium hirsutum) seeds extract are reported. Xerogels obtained by heat or freeze drying were investigated by X-ray diffraction, dynamic light scattering, differential thermal analysis (DTA)/thermogravimetric analysis (TGA), UV–Vis and fluorescence spectroscopy. Effects of drying process on both silica particles and plant extract were evaluated. In vitro release was studied in release media with pH 1.1 and 7.4. The investigated biocomposite systems display a biphasic release profile wherein the diffusion prevails over the dissolution.
    Full-text · Article · Aug 2015 · Journal of Sol-Gel Science and Technology
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    ABSTRACT: The current study describes the renal anomalies of three second trimester fetuses using post-mortem Magnetic Resonance Imaging (pm-MRI). The results were compared with the conventional autopsy. This study demonstrates that without altering the integrity of the human body the pm-MRI using a 7 Tesla machine is a reliable option in describing congenital renal anomalies. Also it reinforces the idea that post mortem imagistic procedures may provide an important adjuvant to conventional autopsy in small gestational age fetuses.
    Full-text · Article · Jul 2015 · Obstetrica si Ginecologie
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    ABSTRACT: A comparative study of three phosphosilicate gels of the 90SiO2-10P2O5 composition obtained from tetraethoxysilane and three phosphorous precursors: triethylphosphate (TEP), triethylphosphite (TEPI) and H3PO4 is performed. 29Si and 31P Magic Angle Spining NMR, X-ray Photoelectron, X-ray Fluorescence and Raman spectroscopies as well as TG analysis are used in order to establish phosphorous precursors and annealing influence on composition and structure of the outcome materials. Unlike the three dimensional silicate network made of Si(OSi)x(OH)4-x species, unreacted TEP (100 % Q1 condensed phosphorous units) from TEP derived gel and a large amount of isolated phosphorous species (39.7 % Q0) in the H3PO4 derived gel are identified. Annealing at 700 C of the three gels give similar structure with the 90SiO2-10P2O5 glass, excepting the triethylphosphate derived glass that has a much lower P content. Thus, the H3PO4 derived glass at 700 and 1000 C shows 1.89 and 1.94 times higher P2O5/SiO2 ratios than in the case of the TEP derived one.
    Full-text · Article · Apr 2015 · Journal of Molecular Structure
  • C. Gruian · E. Vanea · H.-J. Steinhoff · S. Simon
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    ABSTRACT: Understanding protein adsorption to solid surfaces represents a topic of general interest, this phenomenon being crucial for disciplines such as biochemical engineering, biotechnology, biomedicine, biology and environment science. For instance, in the field of biomedicine it is of great importance to assess the adsorption of blood proteins to implants. This complex process is driven by different protein-surface or protein-protein forces and is strongly influenced by parameters like pH, temperature, ionic strength, protein type and by the chemical and physical characteristic of the surface. Despite an increased understanding of many peculiarities of protein adsorption achieved in recent years, there still are unanswered questions or contradictory opinions related to this research topic. The present chapter summarizes some basic characteristics of the protein-adsorption process, with focus on glass-ceramic type materials. The examples of protein adsorption studies described in the present material aim to enlighten aspects related to conformational changes or structural rearrangements of the protein domains upon adsorption, influence of surface functionalization on proteins adsorption and to elucidate details concerning protein dynamics and the amount of the protein attached. Three types of glass-ceramic materials were considered as concrete examples: bioactive glasses designed for tissue engineering, aluminosilicate glass-ceramics intended for both hyperthermia and radiotherapy applications, and silica matrices aiming to be used for therapeutic proteins delivery. Among the many methods used to investigate adsorption of proteins on solid surfaces, three spectroscopic techniques are highlighted: the method of site-directed spin labeling combined with electron paramagnetic resonance, Fourier transform infrared and X-ray photoelectron spectroscopy.
    No preview · Chapter · Jan 2015
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    ABSTRACT: Well-defined calcium molybdate (CaMoO4) and hydroxyapatite (HAP) nanocrystals were developed by thermal treatment on the surface of a SiO2–CaO–P2O5–MoO3 amorphous precursor synthesised at room-temperature by sol–gel route. The structural and morphological characterisaions were performed by several techniques: energy dispersive X-ray spectroscopy, thermal analyses (DTA/TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy, electron paramagnetic resonance. Complementary, Fourier transform infrared and Raman spectroscopies provided a clear picture regarding the short range order structure, emphasising beside the CaMoO4 phase development, the presence of HAP nanocrystals. The vibrational spectroscopic techniques proved to be valuable tools for evidencing very small HAP nanocrystallites that cannot be clearly observed by XRD and TEM analyses.
    No preview · Article · Jan 2015 · Journal of Materials Science
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    ABSTRACT: Gossypol is a polyphenolic compound with a wide range of therapeutic properties. The incorporation of gossypol in a porous gadolinium-silica matrix was considered for both therapeutic effect and contrast in magnetic resonance imaging. The purpose of the study was to evaluate gossypol loading in silica-gadolinium particles prepared at different pH values, as a first step in designing new theranostic (therapeutic and diagnostic) compounds. Silicagadolinium particles of 98SiO2�2Gd2O3 (mol%) composition were prepared following the sol–gel route. The structure of the particles and their loading with gossypol were investigated by X-ray diffraction, dynamic light scattering, Brunauer–Emmett–Teller analysis, differential thermal analysis, Fourier transform infrared spectroscopy, electron paramagnetic resonance and X-ray photoelectron spectroscopy. All results confirmed the highest loading of gossypol on the surface of the particles synthesised at lower pH. The potential application in magnetic resonance imaging (MRI) of silica-gadolinium particles loaded with gossypol was tested through MRI measurements that showed improved contrast properties compared with the pristine silica-gadolinium particles.
    Full-text · Article · Dec 2014 · Journal of Sol-Gel Science and Technology
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    ABSTRACT: The synthesis procedure represents a key aspect in designing the physical and chemical prop-erties of gold nanoparticles. The current study pro-poses a simple approach for gold nanoparticles synthesis using non-thermal plasma. The novelty of the setup consists in producing an in-liquid plasma discharge in argon bubbles that are externally gener-ated in the solution exposed to treatment. Because plasma is the source of active species which are directly involved in gold reduction, no additional reducing agent was necessary. Collagen protein was used as capping agent. A plasma treatment of 10 min is sufficient for obtaining stable colloidal solutions with UV-Vis absorption maximum at 530 nm. Trans-mission electron microscopy images revealed prepon-derant spherical nanoparticles with dimensions in the range of 6–20 nm. The method of synthesis distin-guishes by its good reproducibility, facility, efficiency, and ability to generate stable colloidal nanoparticles after several minutes of plasma exposure.
    Full-text · Article · Aug 2014 · Journal of Nanoparticle Research
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    ABSTRACT: The “build-up” methodology of a composite photocatalyst is a critical issue regarding the showed photocatalytic performance, including the formation of intermediates. To investigate this issue P25/WO3/Au composites were obtained by impregnation (WO3) and subsequent photoreduction (Au) with UV or visible light. The obtained composites’ photocatalytic activity and intermediate formation profiles were evaluated using phenol as a model pollutant. XPS/UPS and DRS methods were used to uncover local coordination, surface chemistry (of the different types of atoms (Ti, W, O and Au) and the band-structure (band-gap, possible electron transitions) of the obtained nanomaterials. The intermediates’ evolution profile and structural peculiarities were successfully correlated and it was shown that each minor structural (bulk or surface) change has a significant impact on the photocatalytic activity and intermediate formation dynamics.
    Full-text · Article · Apr 2014 · Applied Catalysis B Environmental
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    ABSTRACT: Nanostructured hydroxyapatite (HA)-iron oxide composites obtained by a wet-chemical method through co-precipitation were investigated with respect to the changes induced in the samples structure by progressive addition of iron, by thermal treatments carried out at 450 oC, 550 oC and 700oC, and by incubation in simulated body fluid. The structural changes were analysed by X-ray diffraction (XRD), electron paramagnetic resonance (EPR) and magic angle spinning nuclear magnetic resonance (MAS-NMR). After heat treatments, crystalline HA was developed in all samples, even in larger amount in those with iron, showing that iron acts as catalyser for HA development. The MAS-NMR results show as well that only a part of the iron atoms are uniformly incorporated in the HA structure by replacing of calcium. EPR results support that an important part of iron atoms are disposed in regions rich in iron that behave like superparamagnetic or magnetic particles distributed in HA matrix. The analyses carried out on 550 oC treated samples, after three days of immersion in SBF, point out a decrease of HA crystallites size and the appearance on particles surface of a new amorphous calcium phosphate layer.
    Full-text · Article · Mar 2014 · Ceramics International
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    ABSTRACT: In this study, porous titanium compacts obtained by the pressing-sintering route, previously modified by an anodic oxidation treatment, were coated with 3- Aminopropyltriethoxysilane (APTES) in order to facilitate a later immobilization of peptides in view of improving their biocompatibility. The surface of porous titanium before and after modification was characterized by X-ray photoelectron spectroscopy (XPS) and attenuated total refraction-Fourier transform infrared spectroscopy (ATR-FTIR). According to spectral analysis, after the bonding of APTES films on the anodized PM porous titanium surfaces, a new peak located around 1110 cm-1 attributed to siloxane groups suggests that the silane agent had been grafted onto the surface of the modified titanium substrate. Also, after the deposition of APTES films, significant changes were seen in the XPS spectrum, as the peaks corresponding to Ti disappeared, indicating a full silane coverage on the porous surface.
    No preview · Article · Jan 2014 · IFMBE proceedings
  • O Ponta · R Ciceo-Lucacel · A Vulpoi · T Radu · S Simon
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    ABSTRACT: The study is focused on synthesis, investigation of the structural and morphological changes induced by MoO3 addition and thermal treatment, as well as in vitro characterization of a new sol-gel derived SiO2 -CaO-P2 O5 bioactive materials. The obtained systems are composite materials consisting of nanocrystalline apatite, bioactive glass and CaMoO4 nanoparticles, which are of interest for both regenerative medicine and specific medical applications of the releasable molybdenum ions. The changes induced by the thermal treatments and MoO3 addition with respect to the structure and morphology were completed using DTA\TGA, XRD, SEM, EDX, XPS, FTIR, EPR and BET. The biological performance of these materials was evaluated in vitro by performing bioactivity and biocompatibility tests. The bioactive properties in terms of HAp layer formation on the biomaterial surface after SBF immersion were studied by XRD and SEM. In order to establish their biocompatibility, the biomaterials surface was functionalized with protein and the resulted sample was investigated using SEM, FTIR and XPS. The obtained results suggest that the addition of molybdenum oxide in proper concentration improves the biocompatibility in terms of enhancement of protein adherence on Si-Ca-P surface due to CaMoO4 crystalline phase development and does not inhibit bioactivity.
    No preview · Article · Oct 2013 · Journal of Biomedical Materials Research Part A
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    ABSTRACT: The biocompatibility of nanostructured titanosilicate microspheres with different Ti/Si ratios was evaluated by probing the affinity of horse haemoglobin (Hgb) towards the samples surface, in terms of quantitative and conformational changes analysis. The samples morphology before and after protein adsorption was evaluated by Scanning Electron Microscopy (SEM). X-ray Photoelectron Spectroscopy (XPS), Electron Paramagnetic Resonance (EPR) on spin labeled protein and Fourier Transform Infrared (FTIR) spectroscopies were further used to achieve information concerning both the amount of attached haemoglobin and its secondary structure modifications upon adsorption. The obtained results suggest that nanostructured titanosilicate microspheres present a friendly surface for protein adsorption and an enhanced protein adherence with increase of silica content.
    Full-text · Article · Jul 2013 · Journal of Molecular Structure
  • F. Taloş · M. Senilă · T. Frentiu · S. Simon
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    ABSTRACT: The dissolution and surface layer changes of new xTiO2(100 − x)[4SiO2·CaO·0.3P2O5] sol–gel derived xerogels (0 ⩽ x ⩽ 20 mol%) have been investigated in Kokubo’s simulated body fluid (SBF). The ionic leaching rate was analysed by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). ICP-AES results showed a relatively fast dissolution of titanium free sample, with a high release of phosphorous and calcium ions in the first hour of incubation while the release of silicon ions continuously increased up to 6 h of immersion. The titanium dioxide addition up to 20 mol% differently influences the release of phosphorus, calcium and silicon ions, i.e. TiO2 strongly stabilises the phosphorus ions, to a lesser extent the calcium ions, and has almost no effect on the silicon ions release. The structural changes were evaluated using X-ray powder diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The XRD results show that all samples remain mainly amorphous after immersion in SBF. The changes occurred in the surrounding of phosphorous and silicon ions are well reflected in FTIR spectra and they were correlated with the samples stability in SBF.
    No preview · Article · Jul 2013 · Corrosion Science
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    ABSTRACT: Titania/tungsten (VI) oxide/noble metal (gold and platinum) composites were obtained by the means of selective noble metal photodeposition on the desired oxide’s surface (either on TiO2 or on WO3). The noble metal particles’ localization was proved by SEM-EDX, while their size with DRS and TEM. The influence of the noble metal nanoparticles’ position was investigated successfully on the light absorption properties, photocatalytic activity toward oxalic acid and photocatalytic hydrogen production. Major differences were observed in the photocatalytic performance of the catalysts in which only the position of the noble metal was changed. Consequently, highly active composites were obtained, that surpassed the reference catalysts’ (TiO2(Au), TiO2(Pt), WO3(Au), WO3(Pt)) oxalic acid degradation yield and were also quite active for photocatalytic hydrogen production
    Full-text · Article · Jun 2013 · Catalysis Today
  • S. Simon · M. Todea
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    ABSTRACT: Fourier transform infrared (FTIR) and electron paramagnetic resonance (EPR) spectroscopic data obtained for iron doped silica-bismuthate glasses were used to investigate the changes induced in the local structure of samples as the ratio between Bi2O3 and SiO2 content changes from 3 to 0.66. The environment of constituent cations was investigated both in vitreous and partially crystallized samples of same composition. Progressive substitution of Bi2O3 by SiO2 contributes to the structural relaxation of vitreous network and enhances glass stability. By crystallization heat treatment the structural units appear to be more uniform as it results from the narrowing of corresponding IR bands and EPR lines. FTIR data show that more affected by composition and heat treatment is the environment of bismuth than that of silicon. EPR data indicate an ordering tendency with SiO2 content in glasses, while in vitroceramics the iron environment is much uniform in samples with less SiO2 content, where Bi12SiO20 phase is developed.
    No preview · Article · Apr 2013 · Journal of Non-Crystalline Solids