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An in vitro biological and anti-bacterial study on a sol–gel derived silver-incorporated bioglass system

OBJECTIVES The purpose of this study was to evaluate the in vitro antibacterial and biological activity of silver-incorporated bioactive glass system SiO2-CaO-P2O5-Ag2O (AgBG). The bacteriostatic and bactericidal properties of this new quaternary glass system along with the ternary sol-gel glass system SiO2-CaO-P2O5 (BG) have been studied using Escherichia coli as a test micro-organism. The AGBG system thus appears to be a promising material for dental applications, since similar effects might be produced on a film of bacteria and mucous that grows on the teeth. METHODS The SiO2-CaO-P2O5-Ag2O and SiO2-CaO-P2O5 glass systems were synthesized by the sol-gel technique and characterized for their physicho-chemical properties. The antibacterial activity and biological properties were evaluated by determining the minimum inhibitory concentrations (MICs). Release of Ag+ into the culture medium was measured by inductively coupled plasma (ICP) analysis. RESULTS The in vitro antibacterial action of the SiO2-CaO-P2O5-Ag2O was compared with that of its ternary counterpart glass system. The concentrations of Ag-bioglass, in the range of 0.02-0.20 mg of Ag-bioglass per millilitre of culture medium, were found to inhibit the growth of these bacteria. The Ag-bioglass not only acts bacteriostatically but it also elicited a rapid bactericidal action. A complete bactericidal effect was elicited in the early stages of the incubation at Ag-bioglass concentration of 20 mg/ml and the ternary glass system had no effect on bacterial growth or viability. The antibacterial action of Ag-bioglass was exclusively attributed to the leaching of Ag+ ions from the glass matrix. SIGNIFICANCE One of the major advantages of incorporating silver ions into a gel glass system is that the porous glass matrix can allow for controlled sustained delivery of the antibacterial agent to dental material, used even under anaerobic conditions such as deep in the periodontal pocket. This glass system also provides long-term action required for systems which are constantly at risk of microbial contamination.

Suitability evaluation of sol–gel derived Si-substituted hydroxyapatite for dental and maxillofacial applications through in vitro osteoblasts response

UNLABELLED Si-hydroxyapatite (Si-HAP) has been used in orthopedic, dental, and maxillofacial surgery as a bone substitute. OBJECTIVE The aim of this investigation was to study the effect of Si substitution into the hydroxyapatite matrices and evaluate the biocompatibility effects of Si-HAP material in vitro with human osteoblasts. METHODS Silicon-substituted hydroxyapatite (Si-HAP) bioceramic materials were prepared by incorporating small amounts of silicon into the structure of hydroxyapatite [Ca10(PO4)6(OH)2, HAP] through a sol-gel method. A series of silicon substitutions ranging from 0, 1, 3 and 5 mol%, which are comparable to the measured silicon contents in natural bone, were performed. RESULTS Single-phase Si-HAP was obtained upon calcining the as-prepared powders up to 800 degrees C since no secondary phases, such as tricalcium phosphate (TCP), tetracalcium phosphate (TeCP) or calcium oxide (CaO), were identified by X-ray diffraction analysis. The effects of silicon-substituted hydroxyapatite (Si-HAP) materials towards the responses of human osteoblast-like (HOB) cells were investigated and compared with pure hydroxyapatite. SIGNIFICANCE The Si-HAP indicated a significant increase in cell growth density with culture time irrespective of the amount of Si substituted in HAP. A high Si content (5 mol%) appears to promote rapid bone mineralization, since large amount of calcium phosphate minerals started to develop across the ECM by day 31 for a sample containing 5 mol% Si. On the other hand, a high Si content may result in fast dissolution of the material, owing to a decrease of HAP crystallite size, which might not be ideal for cell attachment for prolonged time periods. An optimum level of Si appears to exist at 3 mol%, which balances these effects.

Rietveld structure and in vitro analysis on the influence of magnesium in biphasic (hydroxyapatite and β-tricalcium phosphate) mixtures

The structure of two different Mg-substituted biphasic (HAP and beta-TCP) mixtures along with the biphasic mixtures without substituted Mg(2+) was investigated using Rietveld refinement technique. The substituted Mg(2+) was found in the beta-TCP phase and its influence on the composition has led to an increase in HAP content of Mg-containing biphasic mixtures when compared with the HAP content detected in pure biphasic mixtures. The refined structural parameters of Ca(10)(PO(4))(6)(OH)(2) and beta-Ca(3)(PO(4))(2) confirmed that all the investigated compositions have crystallized in the corresponding hexagonal (space group P6(3)/m) and rhombohedral (space group R3c) structures. The substitution of lower sized magnesium was found preferentially incorporated at the sixfold-coordinated Ca (5) site of beta-TCP, which is due to the strong Ca (5).O interaction among all the five different Ca sites of beta-Ca(3)(PO(4))(2). The in vitro tests using primary culture of osteoblasts showed that all the tested samples are biocompatible and promising materials for in vivo studies.

Far-infrared optical constants of ZnO and ZnO/Ag nanostructures

We report on the synthesis of ZnO nanoplates and ZnO nanoplate/Ag nanoparticle heterostructures via a simple and cost effective wet chemical precipitation method. The prepared samples were characterized for structural and optical properties by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), UV-VIS reflectance, Raman, and FT-IR spectroscopy. The Kramers–Kronig (K–K) method and classical dispersion theory was applied to calculate the far-infrared optical constants such as, refractive index n(ω), dielectric constant e(ω), transverse optical phonon (TO) and longitudinal (LO) optical phonon modes. We determined various optical constant values n(ω) and e(ω) for ZnO nanostructures in the range of 0 to 9 and 0 to 70, respectively. Whereas, for Ag deposition on ZnO nanostructures, the corresponding n(ω) and e(ω) values were found to be increased in the range of 0 to 30 and 0 to 800, respectively. The TO and LO optical phonon modes of ZnO nanoplate/Ag nanoparticle heterostructures were also found to be higher (416 cm−1, 620 cm−1) when compared with corresponding values obtained for ZnO nanoplates (415 cm−1, 604 cm−1).

Study of far infrared optical properties and, photocatalytic activity of ZnO/ZnS hetero-nanocomposite structure

ZnO nanoplates/ZnS nanoparticles as a hetero-nanocomposite structure was prepared by a single pot precipitation method without using any capping ligands or other additives. The morphology of the prepared nanocomposite was studied by scanning electron microscopy (SEM). Optical properties of the prepared samples were studied by UV-visible reflectance and Raman spectroscopy. The FT-IR spectroscopy along with the Kramers–Kronig (k–k) method and classical dispersion theory were utilized to calculate far-infrared optical constants of the prepared samples. The photocatalytic activity of the prepared nanoheterostructure was also assessed in the gas–solid phase, by monitoring the NOx abatement using a white-lamp to re-create an indoor environment.

A Method for Simultaneously Precipitating and Dispersing Nano-Sized Calcium Phosphate Suspensions

Stable and relatively concentrated aqueous suspensions of nano-sized stoichiometric hydroxyapatite could be prepared by a precipitation method in the presence of suitable surface active agent (SAA). The method includes the precipitation, vacuum filtration and washing of the precipitated powders, followed by re-dispersion. It could be concluded that the added amount of the SAA should be enough to cover the primary particles surface, and that washing should be better carried out using a SAA solution. The method developed enables the precipitation of the powders and the preparation of suspensions, while significantly shortening the overall time required for colloidal processing consuming.

Nanocrystalline ZnO–SnO2 mixed metal oxide powder: microstructural study, optical properties, and photocatalytic activity

In this study, nanocrystalline ZnO–SnO2 mixed metal oxide powder was prepared by co-precipitation using Zn(CH3COO)2∙2H2O and SnCl4∙5H2O as precursor materials. The powder was characterized by X–ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. Williamson–Hall method was used to evaluate the micro structural parameters of ZnO–SnO2 such as crystallite sizes and lattice strain. The photoluminescence property of the sample was studied at different temperatures (10–300 K). Results showed that the emission intensity decreases with temperature increasing. The photocatalytic activity at the gas–solid interface was assessed by monitoring the degradation of nitrogen oxides, a major atmospheric pollutant. The results show that the nanocrystalline ZnO–SnO2 mixed metal oxide powder exhibits higher and more stable photocatalytic activity against photocorrosion than ZnO alone.Graphical abstract

Enhanced local piezoelectric response in the erbium-doped ZnO nanostructures prepared by wet chemical synthesis

Abstract Pure and erbium (Er) doped ZnO nanostructures were prepared by simple and cost effective wet chemical precipitation method. The successful doping with phase purity of prepared ZnO nanostructure was confirmed by X-ray diffraction (XRD) and their Rietveld analysis. The change in structural morphology of nanoscale features of prepared ZnO nanopowders on Er doping was observed from their scanning electron microscopy (SEM) images. The presence of Er in prepared ZnO nanopowder was further confirmed from corresponding energy dispersive X-ray spectroscopy (EDX) spectra of scanned SEM images. Piezoelectric properties of before (green samples) and after sintering of consolidated compact of synthesized nanopowders were successfully measured. The out-of-plane (effective longitudinal) and in-plane (effective shear) coefficients of the samples were estimated from the local piezoresponse.

Upconversion Properties of the Er-Doped Y2O3, Bi2O3 and Sb2O3 Nanoparticles Fabricated by Pulsed Laser Ablation in Liquid Media

Er-doped Y2O3, Bi2O3 and Sb2O3 nanoparticles are synthesized using pulsed laser ablation in a liquid. Ceramic targets of Y2O3:Er3+, Bi2O3:Er3+ and Sb2O3:Er3+ for ablation process are prepared by standard solid-state reaction technique and ablation is carried out in 5-ml distilled water using nanosecond Q-switched Nd:YAG laser. The morphology and size of the fabricated nanoparticles are evaluated by transmission electron microscopy and the luminescence emission properties of the prepared samples are investigated under different excitation wavelengths.

Structural and impedance spectroscopy characteristics of BaCO3/BaSnO3/SnO2 nanocomposite: observation of a non-monotonic relaxation behavior

A BaCO3/BaSnO3/SnO2 nanocomposite has been prepared using a co-precipitation method without adding any additives. The prepared sample was characterized by using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR) spectroscopy, energy dispersive X-ray spectroscopy (EDS) and Raman spectroscopy. Detailed studies on the dielectric and electrical behavior (dielectric constant, complex impedance Z*, ac conductivity, and relaxation mechanisms) of the nanocomposite have been performed using the nondestructive complex impedance spectroscopy technique within the temperature range 150–400 K. The dielectric constant of the sample as a function of temperature showed the typical characteristics of a relaxor. The maximum dielectric constant value was observed to depend on frequency. The non-monotonic relaxation behavior of the prepared nanocomposite was evidenced from the spectra of loss tan, tan(δ). The relaxation kinetics was modeled using a non-Arrhenius model.