Days Of Soaking Research Articles

Features of obtaining malt with use of aqueous solutions of organic acids

Recently, the traditional formulations of essential food products are actively including malt – a valuable dietary product rich in extractives and hydrolytic enzymes, obtained by germination in artificially created conditions. Containing a full set of essential amino acids and a high saccharifying ability of malt, obtained from grain cereals, determines its wide use in the production of beer, alcohol, mono- and poly-malt extracts, bakery products, special types of flour, food additives, cereals, non-alcoholic beverages, lactic acid products and, in particular, in the production of natural coffee substitutes. However, the classical germination technology, which includes 2-3 days of soaking and 5-8 days of germination due to the considerable duration and laboriousness of the process, does not meet the requirements of modern technology and the constantly growing rates of industrial production, so this problem requires finding new and improving existing scientific and technical solutions. The features of malt production using organic acids of different concentrations are presented. The malt production technology has been analyzed and investigated. It includes washing, disinfection, air and water soaking of grains, germination and drying. The feature of the technology under investigation is using of aqueous solutions of butadiene, 3-pyridinecarboxylic acid and pteroylglutamic acid. The results of the inquiry of the effect of these organic acids on energy and the ability of germination of the grain are presented. The optimal values of concentrations of active substances in solutions are revealed. The influence of organic acids on the absorption of grain moisture has been investigated. It has been established that in comparison with the classical technology, the use of these acids as a growth stimulator can reduce the overall length of the reproduction process of the material from 1.5 to 2 times and increase the yield of flour grains in the batch of malt.

Synthesis of Glasses and Glass-Ceramics of the System Diopside - Fluorapatite and Characterization of Their in Vitro Bioactivity

AbstractGlasses and glass-ceramics of the system Diopside [D, CaMgSi2O6] - Fluorapatite [FAp, Ca5(PO4)3F] were synthesized and characterized. The studied theoretical phase compositions were (wt%): 1) 70% D-30% FAp, 2) 60% D-40% FAp and 3) 80% D-20% FAp. The glass-ceramics were synthesized by isothermal treatment of the corresponding parent glasses at either 800, 900 or 1000 °C, with holding times of either 30 min, 2 h or 5 h at high temperature. The in vitro bioactivities of all materials were tested in Kokubo’s Simulated Body Fluid (SBF), for 21 days at pH = 7.4 and 37 °C. All materials were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM/EDS). In all cases, the in vitro bioactivity increased with decreasing crystallization degree in the materials, which was likely due to an inhibitory effect of the structural changes occurring during thermal treatment of the glasses. This was more accentuated for long thermal treatments. After 21 days of soaking in the SBF, an apatite-like surface layer, with a Ca/P molar ratio close to 1.67, was formed in the case of the parent glass of composition 2. This was attributed to an enhancing effect of so-called “phase separation” phenomenon that took place during the synthesis of that particular glass. Lastly, the MgO content of the glasses made no clear difference on their in vitro bioactivity.

Preparation and structural characterization of bioactive bredigite (Ca7MgSi4O16) nanopowder

Nanostructured bioceramics are expected to have better bioactivity than coarser crystals. This work aims to prepare, characterize and evaluate the bioactivity of bredigite nanopowder, synthesized by modified sol–gel method. In vitro bioactivity assessment was performed by soaking the samples in the simulated body fluid (SBF) and immersing it for apatite formation on the surface. X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM) techniques were utilized to characterize the nanopowders. The morphological and compositional changes of the samples, after soaking in SBF, were studied and analyzed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), energy dispersive spectroscopy (EDS), and inductively-coupled plasma optical emission spectroscopy (ICP-OES). Results showed that the particle size of pure bredigite was around 38–48 nm. During immersion in SBF, the dissolution rate of the bredigite nanopowder was higher than that of the bredigite micro size powder, and apatite was formed on it after 3 days of soaking.

Synthesis and characterization of bioactive glass coated forsterite scaffold for tissue engineering applications

In recent years forsterite scaffolds have been studied for bone regeneration. Many attempts have been focused on preparing highly porous scaffolds with appropriate mechanical strength and bioactivity. This paper proposes a simple way to improve the compressive strength and bioactivity of forsterite scaffolds by coating them with bioactive glass. Results showed that the scaffolds exhibited high porosity (up to 78%) with pores diameters in the range of 70–245 μm. The maximum values of compressive strength and elastic modulus of the prepared scaffolds were found to be about 7.8 MPa and 309 MPa, respectively. In vitro test in the simulated body fluid proved the good bioactivity of the bioactive glass coated forsterite scaffold while bone like apatite formation started from the first day of soaking, and apatite covered the entire surface and inner wall of the scaffolds pores at short immersion time. The obtained scaffolds provided good mechanical support with remarkable bioactivity so they could be used as tissue engineering scaffolds for load bearing applications.

Polyoxometalate Heterogeneous Nanostructures As Cathodes for Mg2+ Ion Storage

As global energy demands continue to rise each year, current state-of-the-art Li-ion battery (LIB) systems are predicted to reach the limit in the amount of energy that they can supply. In addition to this, LIBs are also limited by the low resource availability of Li metal. One proposed solution is to move away from LIBs to multivalent ion systems; of these alternatives, magnesium (Mg) is considered a promising material for the next generation of rechargeable batteries. Unlike Li, Mg metal does not form dendritic structures during cycling which would allow it to be employed as an anode which has a specific capacity of 2205 mAh/g compared to 777 mAh/g of the graphite anode that is currently used in LIBs. Mg also has a very high elemental abundance in the earth’s crust (2.44x104 ppm) which would drive down the production cost while simultaneously ensuring the longevity of these batteries in terms resource availability. Most importantly, the divalent nature of the Mg-ion means that it can carry twice the amount of charge per ion compared to Li. This is largely related to the high volumetric capacity (3833 mAh/ml) of Mg which is superior to even that of Li metal. While there is potential for Mg to replace LIBs, commercialization of these batteries has been hindered by sluggish insertion kinetics into cathode host materials as a direct result of the strong coulombic interactions experienced by the divalent Mg-ion. Due to this drawback, conventional metal oxide or sulfide insertion cathodes for Mg batteries tend to exhibit low capacities and operating voltages. In response to this, a large portion of Mg battery research is currently focused on the development of novel materials capable of functioning as cathodes for fast and efficient Mg-ion insertion. The idea proposed in this work is to depart from the conventional intercalation mechanism of LIBs and move towards a molecular cluster battery (MCB) based on polyoxometalate (POM) metal oxygen cluster molecules of early transition metals (Mo, W, V, or Nb). The unique redox activity of POMs are due to their intrinsic ability to form highly stable reduced and oxidized species allowing them to partake in fast reversible electron transfer reactions. Although POMs are also able to function as electron reservoirs, POMs themselves have negligible electronic conductivity as well as high solubility in both aqueous and organic media. Therefore, in order for these materials to be used as electrodes for electrochemical energy storage, they must first undergo hybridization with highly conductive insoluble substrates such as conductive organic polymers (COPs) or multi-walled carbon nanotubes (MWCNTs). The fabrication of heterogenous cathodes provide a “wiring” effect by electrically connecting the POM molecules allowing them all to take part in the redox chemistry while simultaneously anchoring them to a substrate, thus preventing any loss of active material to electrolyte dissolution during cycling. By taking advantage of the synergistic effect of pairing the ionically conductive POM molecule with the electrically conductive substrate; the resulting cathode material will thus be capable of fast electron transfer reactions with high ionic mobility. In this work, hybrid nanostructured electrodes of poly-3,4-ethylenedioxythiophene (PEDOT) and a phosphomolybdic acid (H3PMo12O40) POM have been fabricated electrochemically and applied as cathodes for Mg-ion storage. Preliminary cyclic voltammetry and galvanostatic cycling data have demonstrated an enhancement in the capacity of the PEDOT cathode after integration of the POM molecules throughout the polymer matrix. The initial cycling studies have also shown that the PEDOT-POM redox peaks are still present after 7 days of soaking in the organic electrolyte which suggests that the POM molecules do not readily dissolve out of the PEDOT matrix. This work highlights the potential of redox active POM inorganic clusters to function as cathodes with the capability of advancing the current state of Mg batteries.

English

The endo-β-mannanase acts on the hemicellulose fraction of the endosperm cell walls, mainly mannans and galactomannans. This process weakens cell walls and allows radicle protrusion during seed germination, but may also occur during the deterioration process. Thus, the aim of this research was to determine the activity of endo-β-mannanase enzyme in dry coffee seeds and in soaked seeds, evaluating its relationship between physiological qualities. Coffee seeds obtained by different processing methods (natural, fermented and demucilated) and drying (sun, shade and dryer) were used. Seed quality was evaluated by germination and tetrazolium tests, and the endo-β-mannanase enzyme activity was determined in dry seeds and after 10 days of soaking. From the results, it was concluded that there is significant inverse relationship between the physiological quality of coffee seeds and the expression of endo-β-mannanase, and seeds with lower percentages of germination and viability of embryos have a higher activity of the enzyme. After ten days of soaking, coffee seeds had higher expression of endo-β-mannanase as compared to the dry seeds for all treatments of fruit processing and drying. Key words: Coffea arabica L., processing, drying, physiological quality.

Improving the resilient modulus of a gypsum sand roadbed soil by increased compaction

A gypsum sand roadbed soil with about 28% gypsum content was tested in the laboratory for the resilient modulus (MR) and California bearing ratio (CBR) under four different compaction efforts. Twenty-eight pairs of CBR specimens were compacted at the optimum moisture content of modified AASHTO compaction. The first seven pairs were compacted using 10 blows/layer, while the second, third and fourth seven pairs were compacted using 30, 50 and 70 blows/layer, respectively. Each pair of the seven pairs was soaked for a certain period of time namely, 0 (unsoaked conditions), 4, 7, 15, 30, 60 and 120 days under the effect of 40 lbs (178 N) surcharge load. The nondestructive test for measuring MR using New Sonic Viewer was conducted before carrying out the CBR test. The travel times of compression and shear waves were measured to allow the calculation of the resilient modulus before and after each soaking period. The results show that the MR increases with increasing compaction effort but decreases significantly with increasing soaking period. The drops in the MR after 120 days of soaking were 38.7%, 36.84%, 33.53% and 29.15% for 10, 30, 50 and 70 blows/layer, respectively. The paper recommends the strong non-linear correlation developed between MR and CBR for soaked gypsum-rich roadbed sand.

The effect of synthesis parameters on morphology and diameter of electrospun hydroxyapatite nanofibers

In the present study, hydroxyapatite nanofibers were synthesized by electrospinning. The main focus is based on the effect of adding various ratios of calcium phosphate (Ca-P) sol to polymeric solutions of PVA and PVP with a fixed concentration of 10 and 15% (w/v), respectively, on the morphology and the diameter of the electrospun nanofibers. The electrical conductivity of pure PVA solution was higher than PVP (0.610 versus 0.06 mS/cm). However, by adding Ca-P sol, the solution conductivity increased to 23.5 and 34.4 mS/cm for PVA solution containing 15 (vol%) [A15] and PVP solution containing 25 (vol%) [V25] of the prepared sol, respectively. SEM observations showed that the fiber diameter of sample V25 (average diameter of 150 nm) was thinner and more uniform than A15 (average diameter of 170 nm). FE-SEM of sample V25 confirmed the results of SEM analysis as well. After heat treatment at 600 °C, powder-like particles were formed for the samples obtained from PVA solution without any fibers whereas a spaghetti-like morphology was seen for the samples V15 and V25. X-ray diffractograms of sample V25 indicated the presence of HA phase at two temperatures of 600 and 800 °C. However, in the latter case, minor phases of beta-tricalcium phosphate and calcium oxide were also identified. In addition, the crystal size increased from 2 nm at 600 °C to 16 nm at 800 °C.SEM/EDS analyses confirmed the formation of needle-like HA on surface of V25 after 7 days of soaking in simulated body fluid (SBF). Evaluation of cell growth demonstrated that human osteoblast-like cells were attached, spread, and grown well on the surface of V25. This event could be a good sign of biocompatibility of the fibers.

Comparison of short-term and long-term performances for polymer-stabilized sand and clay

Abstract A series of tests were carried out on sulfate rich, high-plasticity clay and poorly-graded natural sand to study the effectiveness of a methylene diphenyl diisocyanate based liquid polymer soil stabilizer in improving the unconfined compressive strength (UCS) of freshly stabilized soils and aged sand specimens. The aged specimens were prepared by exposing the specimens to ultraviolet radiation, freeze-thaw, and wet-dry weathering. The polymer soil stabilizer also mitigated the swelling of the expansive clay. For clay, the observations indicated that the sequence of adding water and liquid polymer had great influence on the gained UCS of stabilized specimens. However, this was shown to be of little importance for sand. Furthermore, sand samples showed incremental gains in UCS when they were submerged in water. This increase was significant for up to 4 days of soaking in water after 4 days of ambient air curing. Conversely, the clay samples lost a large fraction of their UCS when soaked in water; however, their remaining strength was still considerable. The stabilized specimens showed acceptable endurance under weathering action, although sample yellowing due to ultraviolet radiation was evident on the surface of the specimens. Except for moisture susceptibility of the clay specimens, the results of this study suggested the liquid stabilizer could be successfully utilized to provide acceptable strength, durability and mitigated swelling.

Mechanistical study of effect of ions in smart water injection into carbonate oil reservoir

Abstract The concerns for water availability, affordability and environmental consideration have motivated more research on the development of smart water injection for enhanced oil recovery process. Although wettability alteration has been considered as the dominant mechanism, there is an ample space in this area needs to be explored more. Therefore, a systematic series of experiments is designed and performed to examine the effect of salinity and ion type on the wettability of the carbonate rock surface to find the active mechanisms. For this purpose, the concentrations of different salts including NaCl, KCl, CaCl 2 and MgCl 2 are examined during 10 days of soaking for salts concentrations range of 0–45,000 ppm. Based on the measurements of contact angle (CA), it is concluded that the monovalent cation bonded to the chloride anion showed better performance on the wettability alteration of oil wet carbonate rock surface compared to the divalent cations bonded to the chloride anion. In addition, comparing the results of CA measurements of NaCl and KCl solutions as a function of concentration showed completely different wettability behaviors. The presence of KCl shifted the wettability of the carbonate rock surfaces from strongly oil wet to strongly water wet state for all of studied concentrations while as the concentration of NaCl was decreased, the more wettability alteration was observed.

Synthesis of hydroxysodalite zeolite by alkali-activation of basalt powder rich in calc-plagioclase

Hydroxysodalite (H-SOD) microcrystalline particles were synthesized from basalt powder rich in calcic-plagioclase (anorthite) by alkali activation at 80°C/24h. Sodium hydroxide (NaOH) solution was used as alkaline activator. The reactivity of the natural solid precursor basalt was studied using differential scanning calorimetry (DSC), and a maximum reaction enthalpy of (−ΔH) of 170J/g was obtained. The chemical, mineralogical, and textural properties were obtained by using X-ray powder diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and N2-adsorption-desorption measurements. The synthesized material has a specific BET surface area of 20.5m2g−1 approximately 200 times higher than raw basalt material (0.1m2g−1). The compressive strength of basalt based H-SOD/sand composite samples cured at 80°C for 24h upon using different amounts of the activator (NaOH) was evaluated under dry and saturated conditions. The dry samples with NaOH/basalt mass ratio of 0.12 have reached a compressive strength of 57MPa. Wet samples, on the other hand, showed a compressive strength of 25MPa after seven days of soaking in water and four episodes of wetting and drying. The present work illustrates that crystalline H-SOD could be synthesized from cheap basalt powder precursor.

Use of epoxypropoxy-propyl-trimethoxysilane in the fabrication of bioactive gelatin microspheres using an emulsification method

Gelatin microspheres (GMs) using various concentrations of epoxypropoxy-propyl-trimethoxysilane (EPPTMS) as a crosslinking agent were prepared. Since the crosslinking agent content and manufacturing conditions are crucial factors in the characteristics of the microspheres, this study was carried out to evaluate the effect of processing variables on morphology, and in vitro behavior of GMs using acellular simulated body fluid (SBF). It was found that the best morphology was acquired in terms of both shape and uniformity for the GMs containing a certain concentration of EPPTMS (20wt%), whereas other concentrations yielded rambling spheres. The results revealed that the size of microspheres became smaller when both the oil-to-water ratio and agitation rate were increased. Moreover, the density of the crosslinking agent was also dependent on the above-mentioned factors in 20wt% EPPTMS. Different morphologies of hydroxyapatite deposits on the surface of GMs were observed after 14 days of soaking in SBF. These in vitro acellular studies were confirmed by SEM, FTIR, and XRD analyses. According to the results of UV–Vis spectroscopy, the GMs were released into the SBF solution in a time-dependent manner; however, the fastest rate of release occurred for the largest GM.

Effect of solvent composition on the bioactive coating fabricated by micro-arc oxidation combined with electrophoretic deposition

In this work, to improve the bioactivity of titanium (Ti) used as an implant material, an in situ composite coating of hydroxyapatite/titanium dioxide (HA/TiO2) was prepared on the surface of a Ti substrate using electrophoretic deposition combined with a micro-arc oxidation (EPD–MAO) technique in a 0.2M NaOH electrolytic solution with various ethanol concentrations (0, 25 and 50 vol.-%). The addition of ethanol to the electrolytic solution inhibited gaseous emission at the electrode generated by the electrolysis of water and allowed for efficient incorporation of HA particles into the coating layer. The surface morphology, roughness and chemical composition of the coating layer were affected by the ethanol concentration. The corrosion resistance of the sample was examined by potentiodynamic polarisation measurements. The treated sample showed a low corrosion rate compared with an untreated Ti sample. The presence of an apatite-like phase on the treated sample surface after 5 days of soaking in a simulated body fluid (SBF) demonstrates a high bioactivity potential. The cell proliferation assay and alkaline phosphatase (ALP) ability test were used to evaluate osteoblast cell behaviour. The coating layer formed with an electrolytic solution containing 25 vol.-% ethanol showed the greatest cell ability.

Unexpected reaction of new HAp/glucan composite to environmental acidification: Defect or advantage?

Natural polymer-based composites become very popular in design of biomaterials for bone tissue regeneration. Their rheological and mechanical properties are typically evaluated in vitro according to standard methods. However, in vivo such composites may behave completely different due to specific body conditions (e.g., inflammation-assisted acidification of tissue liquids). Such surprising phenomenon was observed for hydroxyapatite/β-1, 3-glucan composite during alveolus extraction socket augmentation in people. Implanted composite showed unexpected massive swelling, caused stitches loosening and wound reopening 5days after implantation. Acidic pH was selected as a potential factor affecting this phenomenon, as all implantations are accompanied by transient local inflammation and acidification. Composite parameters were therefore studied after 5days of soaking in acidic medium by weight and volume measurement, SEM, XRD, FTIR, microCT, and mercury intrusion techniques. Results showed significant volume increase, pore size remodelling and ceramic phase rearrangement in the composite, accompanied by change of mechanical properties. Simple quantitative correction of amount of implanted composite was sufficient to control in vivo appearance of side effects, confirming that pH-related volume increase of HAp/glucan composite is not a disqualifying factor. This strongly suggests the necessity of very detailed and individually designed tests concerning all new polymer-based composite biomaterials before clinical trials. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1178-1190, 2017.

Calcium silicate cements prepared by hydrothermal synthesis for bone repair

Calcium silicate materials have attracted a great deal of interest because of their osteogenesis. The purpose of this study was to use the hydrothermal method without the use of ethanol and an acidic medium to synthesize calcium silicate powder. After mixing the powder with water, the in vitro bioactivity and osteogenesis of calcium silicate cements were examined in comparison with the cement prepared by the sol–gel route. The morphology, phase composition, weight loss, and diametral tensile strength of the cement after soaking in a simulated body fluid (SBF) for different time periods were assayed. Human fetal osteoblasts (hFOBs) cultured on the cement surfaces were used to evaluate the in vitro osteogenesis. The results indicated that after 1 day of soaking in SBF, a precipitated apatite layer was found on the two cement surfaces. Notably, although the two cements were derived from the different powder technologies, there were no significant differences (P>0.05) in bioactivity including phase evolution, morphology change, strength variation, and degradation between cements during soaking in SBF. The hydrothermally-derived calcium silicate cement showed similar cell attachment, proliferation, differentiation, and mineralization expressions compared to the sol–gel-derived cement, but being higher than those obtained in the tissue culture plate. The present results suggest that the calcium silicate cements prepared by a hydrothermal method had an excellent bioactivity and osteogenesis and may be suitable for bone repair.

Characterization of hydroxyapatite coatings deposited by hydrothermal electrochemical method on NaOH immersed Ti6Al4V

The hydrothermal electrochemical method was used to deposit hydroxyapatite coating on Ti6Al4V. In order to improve the bonding strength between the coating and substrate, the substrates were modified by 8 M NaOH solution before the deposition. The effects of immersing time on the substrate, on the hydroxyapatite coating, and on the bonding strength were studied. X-Ray Diffraction, Scanning Electron Microscope, Fourier Transform Infrared Spectroscopy and Drop Shape Analysis Method were applied. And the crystallinity of hydroxyapatite coating was calculated. The results show that immersing treatment effects the phase compositions, the microstructure and the wettability of the substrate surface. A porous, three-dimensional network structure is formed on the Ti6Al4V surface through the NaOH immersion. The pore size and depth increase with the increase of immersing time from 12 to 48 h. The surface microstructure of Ti6Al4V with 60 h′ immersion time was different from the others. The modification treatment can improve the bonding strength between hydroxyapatite coating and the substrate obviously. The value of the bonding strength with the substrate immersed for 48 h is larger than those of the others. A bone-like apatite layer forms on the coating after 3 days of soaking in SBF, implying with good bioactivity of the hydroxyapatite coatings deposited by the method. The surface characteristics of the sample immersed with 48 h are more conductive to the deposition of hydroxyapatite and to the improvement of the bonding strength. The formation mechanism of hydroxyapatite coating deposited by hydrothermal electrochemical method was discussed.

Effect of solvent composition on the bioactive coating fabricated by micro-arc oxidation combined with electrophoretic deposition

In this work, to improve the bioactivity of titanium (Ti) used as an implant material, an in situ composite coating of hydroxyapatite/titanium dioxide (HA/TiO2) was prepared on the surface of a Ti substrate using electrophoretic deposition combined with a micro-arc oxidation (EPD–MAO) technique in a 0.2 M NaOH electrolytic solution with various ethanol concentrations (0, 25 and 50 vol. %). The addition of ethanol to the electrolytic solution inhibited gaseous emission at the electrode generated by the electrolysis of water and allowed for efficient incorporation of HA particles into the coating layer. The surface morphology, roughness and chemical composition of the coating layer were affected by the ethanol concentration. The corrosion resistance of the sample was examined by potentiodynamic polarization measurements. The treated sample showed a low corrosion rate compared with an untreated Ti sample. The presence of an apatite-like phase on the treated sample surface after five days of soaking in a simulated body fluid (SBF) demonstrates a high bioactivity potential. The cell proliferation assay and alkaline phosphatase (ALP) ability test were used to evaluate osteoblast cell behaviour. The coating layer formed with an electrolytic solution containing 25 vol. % ethanol showed the greatest cell ability.

Wollastonite - Tricalcium Phosphate Glass-Ceramics of Eutectic Composition Synthesized by the Glass-Crystallization Method

ABSTRACTGlass-ceramics of eutectic composition in the wollastonite [W, CaO⋅SiO2]- tricalcium phosphate [TCP, β-Ca3(PO4)2] binary system were synthesized by using the glass-crystallization method. The parent glass was crystalized at 800-1300 °C for 0.5-5 h. The in vitro bioactivity of the synthesized glass-ceramics was tested in Kokubo’s Simulated Body Fluid (SBF) for 7-21 days, at pH = 7.4 and 37 °C. All materials were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM/EDS). The results showed that metastable Apatite phase [Ap, Ca10(PO4)6O], plus W and TCP phases expected according to the binary phase diagram, were formed. Ap was the first phase formed at 900 °C/0.5 h, which was followed by formation of W phase at 900 °C/2 h and of TCP phase at 1200 °C/0.5 h. The relative proportion of the formed crystalline phases was a function of heat treatment temperature and time. A eutectic microstructure was obtained for the materials heat-treated at 1300 °C for 2 or 5 h. All glass-ceramics showed the formation of a hydroxyapatite (HAp)-like layer during the in vitro bioactivity tests. After 21 days of soaking in SBF, the samples treated at 1300 °C/5 h showed a behavior similar to that typically shown by Bioeutectic® material, while the materials heat-treated at lower temperatures tended to form denser HAp-like layers, with similar thicknesses but with higher Ca/P molar ratios.

RADIONUCLIDES DISTRIBUTION NEAR FORMER URANIUM MINING

The paper shows, that radionuclides from the stony rocks of uranium mines can be leached by atmospheric precipitations. In acid conditions, a degree of leaching is greater. Goal. The aim of this investigation was to study the distribution of radionuclides in uranium minings and their impact on the environmental contamination. Materials and methods. The study was carried out in two stages. In the first stage, a blade of rock was mixed with distilled water in proportions of 0,3 kg of gravel and 1 liter of water. After thirty days of soaking, water was sent to the gamma-spectrometric analysis to Canberra’s spectrometer (USA) with a high-purity germanium detector. In the second stage, we carried out the similar experiment with water, wich was acidified to pH = 3. Contamination levels of areas near the in-situ leaching mine were determined. Intervention levels were used to estimate risk and possible water consumption by the population. Estimations were carried out taking into account the combined presence of several radionuclides in the water. Results. The results of these studies have shown that the distribution of radionuclides from the source of the contamination is about 360 meters during the 30 y period. The stream, along which samples of soil were collected and studied, was formed by the miner waters that flow along small ruts towards a village, thereby increasing the likelihood of water use by the public. Conclusions. The uranium mines are the source of radioactive contamination. Radionuclides are distributed due to the erosion of rocks and leached out of the stony rock by precipitations. The extent of leaching is significantly increased in an acidic environment, which takes place near the in-situ leaching mines.

P97: Bioresorbable composites based on hydroxyapatite dispersed in poly-L-lactide matrix

Orthopedic oncologic prostheses are essential in postoperative therapy and improvement of life quality of oncological patients. However, construction and composition of implants has to be improved for better biocompatibility and reduction of inflammatory responses. The materials based on polylactic acid (PLA) and hydroxyapatite (HA) have been suggested as promising solution for implant coating in order to improve reconstruction of bone defects, to reduce risk of inflammation and implant rejection. Objective To obtain the bioresorbable composites using biocompatible poly-L-lactide (PLA) with HA and to evaluate its effect on bone remodeling rate. Materials and methods After dissolution of PLA∗ in chloroform the powder-like HA (d = 20–40 nm) was added under vigorous stirring (PLA: HA = 75:25). The PLA/HA suspension was sonicated (40 kHz) and precipitated in ethanol. Fine fibers (d = 0.1– 0.5 μm, of more than 2 mm length) were formed. The PLA/HA composite fibers were air-dried; they consisted of HA nanoparticles homogeneously distributed in the PLA matrix. The composites ability to participate in bone remodeling was estimated by determination of the polymer matrix dissolution rate and by formation of the CPL on the surface of the composites. Results The degradation rate of the polymer matrix was calculated by measuring concentration of lactic acid (by HPLC method), being released from PLA macromolecules as the result of the hydrolysis in the physiologic solution (pH 7, ω(NaCl) = 0.9%). The PLA degradation rate during the first 4 days of soaking of the substrates (d = 10 mm, S = 190 mm2, m = 0.20 ± 0.01 g) in the solution is rather high (Clactic acid = 10 wt%), while on day 5 it decreases and stays constant during the rest of the time. The HA content increase in the composite results in the enhanced hydrolysis of PLA, caused both by the partial acid-base interaction between PLA and HA, and due to presence of the phase boundaries. Interesting to note that pure PLA (without HA) is hardly hydrolyzed in the physiologic solution even on the 30-th day of the experiment. Formation of calcium phosphate layer (CPL) was done in the SBF media, simulating the mineral constituents of the blood plasma at 37 °C, over 28 days period. The total concentration of Ca2+ and Mg2+ ions in the SBF-solution was determined by daily trilonometry in the ammonia buffer with eriochrome black T as indicator. This investigation clearly shows that the substrates both of HA and PLA/HA promote the CLP formation on their surfaces. On day 14 of the substrates soaking in the SBF solution the increment of Ca2+, Mg2+ ions adsorbed on the HA substrate rose to the value of m (Ca2+ + Mg2+)/VSBF = 0.11 mg/l, while the same value on the composite PLA/HA substrate was 0.06 mg/l. Thus the rate of adsorption of Ca2+ ions on the surface of HA is higher than that on the surface of the PLA/HA substrates. It is the result of the high HA content in the material. Pure PLA does not promote adsorption of Ca2+ and Mg2+ ions from the SBF media. Thus the HA particles incorporated in the PLA matrix may cause fast the CLP formation improving the ossification in the bone reconstruction processes. Biocompatibility and anti-inflammatory activity of PLA, HA and PLA/HA composite was studied in a pilot experiment in the cell-mediated immune response of individual donors in vitro using CD14+ human monocytes. Insignificant pro-inflammatory cytokine secretion of the M1 type (TNFα) is observed in the presence of PLA, while HA and PLA/HA composites don’t contribute to their release. The PLA promotes the release of M2 cytokine CCL18 on day 6 of macrophage culturing suggesting potential anti-inflammatory properties of the material. Conclusion The composite PLA/HA supports active bone-like layer formation on its surface improving ossification in the bone reconstruction process. The pilot experiment suggested that PLA/HA does not cause inflammatory reactions, while PLA can potentially regulate the balance between M1/M2 reaction to suppress unnecessary inflammation. ∗Mol. mass ca 60 kDa, prepared in the Laboratory of Catalytic Research of Tomsk State University. This Research is supported by Tomsk State University Competitiveness Improvement Program . The work was partially supported by the project Russian Foundation for Basic Research RFBR # 15-08-05496_a and EU IMMODGEL project, Grant No. (602694). Work was conducted with the application of the Tomsk regional common use center technical equipment acquired thanks to a grant of the Russian Ministry of the Agreement No. 14.594.21.0001 (RFMEFI59414X0001).