[Show abstract][Hide abstract] 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
Ceramics International 10/2015; in press(1). DOI:10.1016/j.ceramint.2015.10.004 · 2.61 Impact Factor
[Show abstract][Hide abstract] 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.
Journal of Sol-Gel Science and Technology 08/2015; DOI:10.1007/s10971-015-3828-8 · 1.53 Impact Factor
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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.
Journal of Sol-Gel Science and Technology 12/2014; 72(3). DOI:10.1007/s10971-014-3482-6 · 1.53 Impact Factor
[Show abstract][Hide abstract] 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.
Journal of Nanoparticle Research 08/2014; 16(10). DOI:10.1007/s11051-014-2633-6 · 2.18 Impact Factor
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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
Ceramics International 03/2014; 40(7). DOI:10.1016/j.ceramint.2014.03.124 · 2.61 Impact Factor
[Show abstract][Hide abstract] 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.
Journal of Biomedical Materials Research Part A 10/2013; DOI:10.1002/jbma.34989 · 3.37 Impact Factor
[Show abstract][Hide abstract] 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
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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
[Show abstract][Hide abstract] 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.
Journal of Non-Crystalline Solids 04/2013; Journal of Non-Crystalline Solids:2947-2951. DOI:10.1016/j.jnoncrysol.2006.04.022 · 1.77 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Aluminosilicate microspheres obtained by spray drying were investigated in prospect of their potential biomedical applications. The as-prepared microspheres are amorphous. TEM and AFM were used to examine the morphology of the samples before and after immersion in simulated body fluid (SBF). The local structure changes as a function of microspheres composition and due to their immersion in SBF were investigated by 29Si and 27Al MAS–NMR. After SBF immersion, the silica network partially depolymerised by hydration/hydroxylation and the completely changed aluminium environment suggest a phylosilicate-like structure. 31P MAS–NMR analysis evidenced phosphorus ions incorporated in a new crystalline phase developed during SBF immersion.Highlights► Aluminosilicate microspheres less than 20 μm were prepared by spray drying. ► Microspheres structure is modified after immersion in simulated body fluid (SBF). ► Silica network is partially depolymerized by hydration/hydroxylation in SBF. ► After SBF immersion the aluminum environment is completely changed. ► Apatite type nanocrystals grown on microspheres in SBF mark their bioactivity.
[Show abstract][Hide abstract] ABSTRACT: The study aims to characterize surface properties of aluminosilicate
microspheres incorporating yttrium, with potential biomedical
applications. Micrometric particles of spherical shape were obtained by
spray drying method. The behavior of aluminosilicate microspheres
without yttrium and with yttrium was investigated under in vitro
conditions, by seven days incubation in simulated body fluid (SBF). The
surface elemental composition and the atomic environments on outermost
layer of the microspheres, prior to and after incubation in SBF were
evaluated by X-ray photoelectron spectroscopy (XPS) in order to
investigate their bioactivity. The results were analyzed to underline
the effect of yttrium addition on surface properties of the
aluminosilicate microspheres and implicitly on the behavior of the
samples in simulated body environments.
[Show abstract][Hide abstract] ABSTRACT: Calcium pyrophosphate nanocrystals incorporated in an amorphous silica based matrix were obtained by sol-gel process followed by heat treatment applied at 550 °C. The resulted nanocomposite was characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The surface reactivity of the nanocomposite was investigated in simulated body fluid (SBF) at 37°C up to 21 days. The results point out that the calcium pyrophosphate nanocrystals induce the oriented growth of bioactive apatite-like crystals on the surface of the investigated nanocomposite.
Digest Journal of Nanomaterials and Biostructures 01/2013; 8:219-225. · 0.95 Impact Factor