Hydroxyapatite/Silver Nanoparticles Powders as Antimicrobial Agent for Bone Replacements

This paper reports a superficial morphological modification of the hydroxyapatite grains obtained by in situ deposition of Ag nanoparticles on natural origin calcium phosphate powder. Ceramic material was prepared in three stage bone treatment, including hydrolysis with a lactic acid, pre-calcination, and proper calcination. Subsequently, the Ag nanoparticles were synthesized by chemical reduction of Ag+ by sodium borohydride in a solution of polyvinylpyrrolidone and in presence of hydroxyapatite. Such-prepared materials were investigated with X-ray diffraction, Fourier-transformed infrared spectroscopy, atomic absorption spectrometry and scanning electron microscopy with energy dispersive spectroscopy. Furthermore, Ca/P molar ratio was calculated and microbiological tests were performed to investigate materials antimicrobial activity. The appearance of Ag nanoparticles located on phosphate surface was confirmed by SEM analysis, and no chemical bonding with hydroxyapatite was recorded by IR and XRD techniques. Additionally, the biological assessment revealed bactericidal effect on Escherichia coli and Staphylococcus aureus, while slightly affected on Enterococcus faecalis viability. This work is licensed under a Creative Commons Attribution 4.0 International License

The effect of glycerin content in sodium alginate/poly(vinyl alcohol)- based hydrogels for wound dressing application

The impact of different amounts of glycerin, which was used in the system of sodium alginate/poly(vinyl alcohol) (SA/PVA) hydrogel materials on the properties, such as gel fraction, swelling ability, degradation in simulated body fluids, morphological analysis, and elongation tests were presented. The study shows a significant decrease in the gel fraction from 80.5 2.1% to 45.0 1.2% with the increase of glycerin content. The T5 values of the tested hydrogels were varied and range from 88.7 C to 161.5 C. The presence of glycerin in the matrices significantly decreased the thermal resistance, which was especially visible by T10 changes (273.9 to 163.5 C). The degradation tests indicate that most of the tested materials do not degrade throughout the incubation period and maintain a constant ion level after 7-day incubation. The swelling abilities in distilled water and phosphate buffer solution are approximately 200–300%. However, we noticed that these values decrease with the increase in glycerin content. All tested matrices are characterized by the maximum elongation rate at break in a range of 37.6–69.5%. The FT-IR analysis exhibits glycerin changes in hydrogel structures, which is associated with the cross-linking reaction. Additionally, cytotoxicity results indicate good adhesion properties and no toxicity towards normal human dermal fibroblasts

POTENTIAL APPLICATION OF NANOMETALS IN ENVIRONMENTAL PROTECTION

In recent years, great interest in metallic nanoparticles has been observed, both because of their unlimited application possibilities, and also because of the unusual biological, chemical and physical features. It is expected that developments in nanotechnology will become the main promoter of scientific and technological innovations in the coming decades. Searching for a new and safe alternative to chemical pesticides, high hopes are associated with nanotechnology development. Particularly useful may be preparations containing nanoscale metal particles with strong antimicrobial properties. Importantly, safe and non-toxic for the plant components of biological origin may be used in nanoparticles synthesis. This article is a description of the potential applications of nanomaterials in environmental protection, which may become the basis for developing of new protection plant products with antimicrobial properties relative to plant pathogens and non-toxic to higher organisms

Impact of the Type of Crosslinking Agents on the Properties of Modified Sodium Alginate/Poly(vinyl Alcohol) Hydrogels

Here, we report on studies on the influence of different crosslinking methods (ionic and chemical) on the physicochemical (swelling ability and degradation in simulated body fluids), structural (FT-IR spectra analysis) and morphological (SEM analysis) properties of SA/PVA hydrogels containing active substances of natural origin. First, an aqueous extract of Echinacea purpurea was prepared using a Soxhlet apparatus. Next, a series of modified SA/PVA-based hydrogels were obtained through the chemical crosslinking method using poly(ethylene glycol) diacrylate (PEGDA, Mn = 700 g/mol) as a crosslinking agent and, additionally, the ionic reaction in the presence of a 5% w/v calcium chloride solution. The compositions of SA/PVA/E. purpurea-based hydrogels contained a polymer of natural origin—sodium alginate (SA, 1.5% solution)—and a synthetic polymer—poly(vinyl alcohol) (PVA, Mn = 72,000 g/mol, 10% solution)—in the ratio 2:1, and different amounts of the aqueous extract of E. purpurea—5, 10, 15 or 20% (v/v). Additionally, the release behavior of echinacoside from the polymeric matrix was evaluated in phosphate-buffered saline (PBS) at 37 °C. The results indicate that the type of the crosslinking method has a direct impact on the release profile. Consequently, it is possible to design a system that delivers an active substance in a way that depends on the application

Studies on sintering process of synthetic hydroxyapatite

In this study the effect of sintering process in different temperatures on microstructure and morphological properties of sintered hydroxyapatite (HAp) was investigated. HAp powder was prepared by wet precipitation method from following reagents: Ca(OH)2 + H3PO4 in an alkaline conditions. Thermal analysis (TA), X-Ray diffraction method (XRD), FT-IR spectrometry (FT-IR) and scanning electron microscopy (SEM) were used to elaborate the phase composition and properties of sintered HAp samples and raw HAp powder as well. The total and apparent density and total porosity of sintered compacts, shrinkage and weight loss during the sintering were also measured. The results show that there is a difference in sintering behavior of synthetic hydroxyapatites depending on sintering temperature. The main differences refer to the loss of mass, shrinkage, changes in porosity and density of the investigated materials

SILVER NANOPARTICLES SYNTHESIS WITH DIFFERENT CONCENTRATIONS OF POLYVINYLPYRROLIDONE

The effect of poly(N-vinylpyrrolidone) (PVP) concentration on the synthesis and properties of silver nanoparticles (AgNPs) was investigated. Nanoparticles have been prepared by a chemical reduction method from the aqueous solution of silver nitrate and PVP as a stabilizing agent in the presence of sodium borohydride as a reducing agent. The nanosized silver colloids have been characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), UV-Vis spectroscopy and transformed infrared spectroscopy (FT-IR). Dynamic Light Scattering (DLS) measurements using Zetasizer Nano ZS were applied to size estimation of AgNPs. The results confirmed that silver nanoparticles were formed in each sample independently of PVP content, however the stabilizer concentration in range of 1.0 % to 10.0 % leads to the synthesis of AgNPs with a size in the narrow range of nano-scale and small amounts of larger clusters. The PVP content had a significant influence on silver nanoparticles morphology and optical properties