Effect of silver additive on physicochemical properties of hydroxyapatite applied to reconstructive surgery

The effect of silver adding to hydroxyapatite (HA) in its solubility in physiological solution and biological activity was investigated. Samples of HA containing silver (AgHA) obtained by liquid-phase method in the conditions of microwave exposure. Solubility (CCa2+·103, mol/l) of the powders AgHA was determined by chemical methods according trilonometric titration of the calcium ions in physiological solution at 25 and 37 °C. To investigate the biological activity of the samples, a series of experiments on the formation of the calcium-phosphate layer on the surface of the SBF-solution at 37 °C for 28 days. Electronic micrographs of samples taken at the end of each 7 days of the experiment, indicate the formation of calcium-phosphate layer (CPL) in the samples, the kinetics of which is shown as a function of cumulative concentrations of calcium and magnesium ions from time

Structural-phase state and surface properties of composite materials based on polylactide and hydroxyapatite

The phase composition and unit cell parameters were determined for composites based on polylactide and hydroxyapatite with the polylactide/hydroxyapatite weight ratios of 90/10, 80/20, 70/30, and 60/40. As the polylactide content of the composites is increased, they become less hydrophilic, and the surface energy σS-G increases from 29.13 to 74.35 mJ m–2. The sample with the component weight ratio of 70/30 is characterized by the maximal roughness, and the Ca2+ and Mg2+ ions from simulated body fluid are actively adsorbed onto its surface, as proved by SEM examination of the composites

Synthesis and investigation of physico-chemical, antibacterial, biomymetic properties of silver and zinc containing hydroxyapatite

In the work we carried out microwave synthesis of modified hydroxyapatites (HA) with different content of ions. A solid solution based on HA remains a single-phase sample when the calcium ions are substituted by silver and zinc ions up to 5 % by weight (0.5 mole fraction). The microstructure parameters, morphology and the particle powders size were studied by X-ray diffraction analysis, IR spectroscopy, and scanning electron microscopy (SEM). It is shown that the modification of НA by silver (AgHA) and zinc (ZnHA) ions increases the size of its particles, the degree of crystallinity, and the pore sizes of the samples while reducing their specific surface and uniformity of their forms. Elemental analysis and distribution of elements over the surface of HA, AgHA, and ZnHA powders were performed by X-ray spectral microanalysis (RSMA). The ratio of Ca/P is within the range of 1.66-1.77 and corresponds to the ratio of Ca/P in stoichiometric HA and the HA entering bone tissue. The ability of AgHA- and ZnHA-substrates to form on their surface a calcium-phosphate layer from the simulated body fluid (SBF) at 37 °C is determined. This ability decreases in the order: in ZnHА it is less than in AgHА, but greater than in HА. The antibacterial activity of the samples was analyzed. The AgHA sample has both bactericidal and persistent bacteriostatic properties in the case of direct contact with Escherichia coli cells

Preparation of composite materials based on hydroxyapatite and lactide and glycolide copolymer

Composite materials for the restoration of bone tissues based on hydroxyapatite and a copolymer of lactide and glycolide were obtained. The composition of materials at different stages of production is estimated by X-Ray diffraction method. It has been established that during the production of materials a new phase of chlorine-substituted hydroxyapatite (Ca9.7(P6O23.81)Cl2.35(OH)2.01) was formed, which promoted an increase of hydroxyapatite solubility in the composition of materials. The quantitative estimation of micro- and macroporosity of materials is given. It was found that the use of sodium chloride as the pore-forming agent delivers porosity of the composites required for use as bone substitutes

Mechanisms of particles in sensitization, effector function and therapy of allergic disease

Humans have always been in contact with natural airborne particles from many sources including biologic particulate matter (PM) which can exhibit allergenic properties. With industrialization, anthropogenic and combustion-derived particles have become a major fraction. Currently, an ever-growing number of diverse and innovative materials containing engineered nanoparticles (NPs) are being developed with great expectations in technology and medicine. Nanomaterials have entered everyday products including cosmetics, textiles, electronics, sports equipment, as well as food, and food packaging. As part of natural evolution humans have adapted to the exposure to particulate matter, aiming to protect the individual's integrity and health. At the respiratory barrier, complications can arise, when allergic sensitization and pulmonary diseases occur in response to particle exposure. Particulate matter in the form of plant pollen, dust mites feces, animal dander, but also aerosols arising from industrial processes in occupational settings including diverse mixtures thereof can exert such effects. This review article gives an overview of the allergic immune response and addresses specifically the mechanisms of particulates in the context of allergic sensitization, effector function and therapy. In regard of the first theme (i), an overview on exposure to particulates and the functionalities of the relevant immune cells involved in allergic sensitization as well as their interactions in innate and adaptive responses are described. As relevant for human disease, we aim to outline (ii) the potential effector mechanisms that lead to the aggravation of an ongoing immune deviation (such as asthma, chronic obstructive pulmonary disease, etc.) by inhaled particulates, including NPs. Even though adverse effects can be exerted by (nano)particles, leading to allergic sensitization, and the exacerbation of allergic symptoms, promising potential has been shown for their use in (iii) therapeutic approaches of allergic disease, for example as adjuvants. Hence, allergen-specific immunotherapy (AIT) is introduced and the role of adjuvants such as alum as well as the current understanding of their mechanisms of action is reviewed. Finally, future prospects of nanomedicines in allergy treatment are described, which involve modern platform technologies combining immunomodulatory effects at several (immuno-)functional levels

Bioactivity and physico-chemical properties of composites on basis of hydroxyapatite with lactic and glycolic acids oligomers

A new method in situ for producing of biocompatible composites based on hydroxyapatite and oligomers of lactic and glycolic acid is described. Their thermo-mechanical, physical-chemical and biological properties are studied as well. The formation of bonds between hydroxyapatite with lactic and glycolic oligomers in composites are confirmed by IR spectroscopy of the samples, including those obtained in the Soxhlet apparatus. The formation of calciumphosphate layer on the surface of composite containing hydroxyapatite was shown by SBFinvestigation. The scaffolds based on lactic acid oligomer do not stimulate formation of a calciumphosphate layer and they are subjected to destruction by the way of hydrolysis

The dependence of cylindrical resonator natural frequencies on the fluid density

The article examines the dependence of cylindrical resonator natural frequencies (sensitive element) on the density (mass) of different fluids flowing through it. The cylindrical resonators are being widely applied in automatic control systems of technological processes as oscillating transducer density meter. The article presents the experimental results that prove the dependence of natural frequencies and vibration amplitude on the fluid density

Iron(III) complexation with barbituric and 2-thiobarbituric acids in aqueous solution

Complexation in systems containing iron(III) chloride and barbituric (H2BA) or 2-thiobarbituric (H2TBA) acid has been studied by spectrophotometry and pH-metry in the pH range of 1.3–3.3 (I = 0.1 (NaCl), t = 20°C). The presence of 1 : 1 complex particles with both mono- and deprotonated forms of the ligand has been established, and their stability constants (in log units) have been determined: [FeHBA]2+(3.49 ± 0.15), [FeHTBA]2+ (2.69 ± 0.07), [FeBA]+ (12.22 ± 0.13), and [FeTBA]+ (11.05 ± 0.08). It has been shown that the higher thermodynamic stability of barbiturate complexes compared to 2-thiobarbiturate complexes is due to the greater basicity of the barbiturate anion. Based on the stability constants obtained, it has been proposed to use orthophosphate, fluoride, and ethylenediaminetetraacetate ions to eliminate the interfering effect of iron(III) in the determination of malondialdehyde by the thiobarbiturate method. Orthophosphoric acid is the most convenient for practical applications, as it makes it possible both to mask iron(III) and to create a strongly acidic medium necessary for the formation of a colored malondialdehyde–H2TBA adduct