Cornstarch aerogels with thymol, citronellol, carvacrol, and eugenol prepared by supercritical CO2- assisted techniques for potential biomedical applications.

This study focuses on the development of bioactive materials using environmentally friendly techniques, renewable, biocompatible, and biodegradable polysaccharide, as well as natural bioactive compounds (NBCs) found in plant extracts. First, cornstarch aerogels with a porosity of 86 % and a specific surface area of 225 m2/g were produced via supercritical CO2- assisted drying. Further, thymol, citronellol, carvacrol, and eugenol were incorporated into the aerogels by supercritical CO2- assisted impregnation, which allowed variation in loadings of NBCs (12.8-17.6 %). Interaction between cornstarch aerogels and NBCs determined impregnation rate, pore wall thickness (in the range 18-95 nm), liquid absorption capacity (from 265 to 569 %), dehydration mass loss, and release in phosphate-buffered saline. Controlled release of NBCs was maintained over a 3-day period. Moreover, impregnated aerogels showed a significant antioxidant effect with the highest value for DPPH radical inhibition of 25.5 % determined for the aerogels impregnated with eugenol. Notable antimicrobial activity against tested Gram-negative bacteria, Gram-positive bacteria, and fungi was also observed, being the highest for thymol-loaded aerogel with the diameter of the inhibition zones of up to 37.5 mm. This work shows a promising green approach for the production of bioactive two-component starch-based materials for potential applications in skin infection treatment.

Synthesis and characterization of luminescent Cu2+-doped fluorapatite nanocrystals as potential broad-spectrum antimicrobial agents.

Nanomaterials based on metal-doped fluorapatite (FAP) have attracted considerable interest as potential next-generation antimicrobial agents. In this study, Cu2+-doped FAP nanocrystals have been successfully synthesized by a neutralization method at room temperature. Their structural, optical, antimicrobial, and hemcompatible properties have been investigated. XRD, FTIR, FESEM, and N2 adsorption-desorption studies indicate the formation of single-phase FAP mesoporous nanopowders, composed of rod-like particles. TEM images confirmed the formation of nanorodes with a length of 60 nm and a width of about 18 nm. Rietveld analysis shows that the Cu2+ ions preferentially substitute Ca2 (6 h) sites in the hexagonal fluorapatite crystal structure. Fluorescence spectroscopy accompanied by MCR-ALS method confirms substitution of Cu2+ ions in FAP crystal lattice with extracting additional d-d band transition at green color from FAP broadband self-activated luminescence in violet-blue color. Antimicrobial studies conducted on Staphylococcus aureus, Escherichia coli and Micrococcus lysodeikticus showed that FAP nanopowder with the highest Cu2+ content have strong bacteriostatic action on Staphylococcus aureus bacterial strain in mediums containing nutrition matters. In addition, this sample in comparison to pure FAP achieved a high percentage of relative reduction of bacterial population for all three species, being >90% in most cases. Fungistatic action is noticed too, throwgh the slowing down mycelium growth of fungus Aspergillus niger, Aspergillus flavus and Penicillium roqueforti and reduction of sporulation of Aspergillus niger species. Cu2+-doped FAP nanocrystals shows a synergistic antimicrobial effect with Cu2+ and F- ions. Concerning the potential biomedical applications, the hemolysis ratios of the Cu2+-doped FAP samples were below 5%. The obtained results pointed out the possible use of the synthesized nanocrystals as broad-spectrum antimicrobial agents for various biomedical and health care preparations.

Antioxidant and cell-friendly Fe2TiO5 nanoparticles for food packaging application.

An emerging technology of active packaging enables prolongation of food shelf life by limiting the oxygen transfer and the reactivity of free radicals, which both destruct food freshness. In this work, Fe2TiO5 nanoparticles were synthesized using a modified sol-gel method and evaluated as an enforcement of alginate food packaging film. Pure phase Fe2TiO5 nanoparticles had an average particle size of 44 nm and rhombohedral morphology. Fe2TiO5 nanoparticles induce no cell damage of human Caco-2 epithelial cells and show no inhibitory effect towards growth of a panel of bacterial strains, suggesting good biocompatibility. Films obtained by incorporation of Fe2TiO5 nanoparticles into alginate using the solvent casting method show no migration of iron or titanium ions from films to food simulants again suggesting their safety as a packaging material. Fe2TiO5 nanoparticles also showed strong antioxidant efficiency as determined using the DPPH assay, and confirmed further in a preservation test on fresh fruit.

Adsorption of estrone, 17ß-estradiol, and 17α-ethinylestradiol from water onto modified multi-walled carbon nanotubes, carbon cryogel, and carbonized hydrothermal carbon.

Carbon materials of different structural and textural properties (multi-walled carbon nanotubes, carbon cryogel, and carbonized hydrothermal carbon) were used as adsorbents for the removal of estrone, 17ß-estradiol, and 17α-ethinylestradiol from aqueous solutions. Chemical modification and/or activation were applied to alter surface characteristics and to increase the adsorption and desorption efficiency of carbon materials. Surfaces of treated and untreated carbon materials were characterized through the examination of the textural properties, the nature of surface functional groups, and surface acidity. It was found that the adsorption capacity of tested carbon materials is not directly proportional to the specific surface area and the content of surface oxygen groups. However, a high ratio of surface mesoporosity affected the adsorption process most prominently, by increasing adsorption capacity and the rate of the adsorption process. Adsorption of estrone, 17ß-estradiol, and 17α-ethinylestradiol followed pseudo-second-order kinetic model, while the equilibrium adsorption data were best fitted with the Langmuir isotherm model. Calculated mean adsorption energy values, along with the thermodynamic parameters, indicated that removal of selected hormones was dominated by the physisorption mechanism. High values of adsorption efficiency (88-100 %) and Langmuir adsorption capacities (29.45-194.7 mg/g) imply that examined materials, especially mesoporous carbon cryogel and multi-walled carbon nanotubes, can be used as powerful adsorbents for relatively fast removal of estrogen hormones from water.

Surface-modified ZrO2 nanoparticles with caffeic acid: Characterization and in vitro evaluation of biosafety for placental cells.

The toxicity of hybrid nanoparticles, consisting of non-toxic components, zirconium dioxide nanoparticles (ZrO2 NPs), and caffeic acid (CA), was examined against four different cell lines (HTR-8 SV/Neo, JEG-3, JAR, and HeLa). Stable aqueous ZrO2 sol, synthesized by forced hydrolysis, consists of 3-4 nm in size primary particles organized in 30-60 nm in size snowflake-like particles, as determined by transmission electron microscopy and direct light scattering measurements. The surface modification of ZrO2 NPs with CA leads to the formation of an interfacial charge transfer (ICT) complex followed by the appearance of absorption in the visible spectral range. The spectroscopic observations are complemented with the density functional theory calculations using a cluster model. The ZrO2 NPs and CA are non-toxic against four different cell lines in investigated concentration range. Also, ZrO2 NPs promote the proliferation of HTR-8 SV/Neo, JAR, and HeLa cells. On the other hand, hybrid ZrO2/CA NPs induced a significant reduction of the viability of the JEG-3 cells (39 %) for the high concentration of components (1.6 mM ZrO2 and 0.4 mM CA).

Exploring the impact of calcination parameters on the crystal structure, morphology, and optical properties of electrospun Fe2TiO5 nanofibers.

Nanostructured Fe2TiO5 (pseudobrookite), a mixed metal oxide material holds significant promise for utilization in energy and environmental applications. However, its full application is still hindered due to the difficulty to synthesize monophasic Fe2TiO5 with high crystallinity and a large specific surface area. Herein, Fe2TiO5 nanofibers were synthesized via a versatile and low-cost electrospinning method, followed by a calcination process at different temperatures. We found a significant effect of the calcination process and its duration on the crystalline phase in the form of either pseudobrookite or pseudobrookite-hematite-rutile and the morphology of calcined nanofibers. The crystallite size increased whereas the specific surface area decreased with an increase in calcination temperature. At higher temperatures, the growth of Fe2TiO5 nanoparticles and simultaneous coalescence of small particles was noted. The highest specific surface area was obtained for the sample calcined at 500 °C for 6 h (S BET = 64.4 m2 g-1). This work opens new opportunities in the synthesis of Fe2TiO5 nanostructures using the electrospinning method and a subsequent optimized calcination process for energy-related applications.

Bone Mineral Crystallinity Governs the Orchestration of Ossification and Resorption during Bone Remodeling.

The circularly causal orchestration of bone production and destruction is a part of the standard model of bone remodeling, but the crystallinity of the bone mineral, which naturally alternates during this process, has not had a steady place in it. Here we show that osteoclasts and osteoblasts, the cells resorbing and building bone, respectively, can sense the crystallinity of the bone mineral and adjust their activity thereto. Specifically, osteoblastic MC3T3-E1 cells secreted mineral nodules more copiously when they were brought into contact with amorphous calcium phosphate (ACP) nanoparticles than when they were challenged with their crystalline, hydroxyapatite (HAp) analogues. Moreover, the gene expressions of osteogenic markers BGLAP, ALP, BSP-1, and RUNX2 in MC3T3-E1 cells were higher in the presence of ACP than in the presence of HAp. At the same time, the dental pulp stem cells differentiated into an osteoblastic phenotype to a degree that was inversely proportional to the amount and the crystallinity of the mineral added to their cultures. In contrast, the resorption of HAp nanoparticles was more intense than the resorption of ACP, as concluded by the greater retention of the latter particles inside the osteoclastic RAW264.7 cells after 10 days of incubation and also by the time-dependent free Ca2+ concentration measurements in the cell culture media at early incubation time points (<1 week), prior to the spontaneous crystallization of the amorphous phase. A detailed morphological, compositional, and microstructural characterization of ACP and HAp is provided too, and it is shown that although ACP transforms to HAp in the cell culture media, some microstructural properties are retained in the powder following this transformation, influencing the resorption rate. On the basis of these findings, a model of bone remodeling at the level of individual biogenic apatite nanoparticles was proposed, taking into account the effects of hydration and lattice strain. According to this model, apatite is a "living" mineral, undergoing fluctuations in crystallinity within a closed ossifying/resorptive feedback loop in a way that buffers against potential runaway effects. A finite degree of amorphousness of every apatite crystal in bone is seen as a vital prerequisite for a healthy, dynamic bone remodeling process, and the best bone mineral, from this standpoint, is the living mineral, the one undergoing a constant process of structural change in response to biochemical stimuli thanks to its partially amorphous microstructure and unique interfacial dynamics.

Surfactant-assisted microwave processing of ZnO particles: a simple way for designing the surface-to-bulk defect ratio and improving photo(electro)catalytic properties.

ZnO nanopowders were produced using microwave processing of a precipitate and applied as a photoanode for photoelectrochemical water splitting. Two different surfactants, cetyltrimethylammonium bromide (CTAB) as the cationic and Pluronic F127 as the non-ionic one, were employed to in situ adjust the surface-to-bulk defect ratio in the ZnO crystal structure and further to modify the photo(electro)catalytic activity of the ZnO photoanode. The crystal structure, morphological, textural, optical and photo(electro)catalytic properties of ZnO particles were studied in detail to explain the profound effects of the surfactants on the photoanode activity. The ZnO/CTAB photoanode displayed the highest photocurrent density of 27 mA g-1, compared to ZnO (10.4 mA g-1) and ZnO/F127 photoanodes (20 mA g-1) at 1.5 V vs. SCE in 0.1 M Na2SO4 under visible illumination of 90 mW cm-2. A significant shift of the overpotential toward lower values was also observed when photoanodes were illuminated. The highest shift of the overpotential, from 1.296 to 0.248 V vs. SCE, was recorded when the ZnO/CTAB photanode was illuminated. The ZnO/CTAB photoanode provides efficient charge transfer across the electrode/electrolyte interface, with a longer lifetime of photogenerated electron-hole pairs and reduced possibility of charge recombination. The photoconversion efficiency was improved from 1.4% for ZnO and 0.9% for ZnO/F127 to 4.2% for ZnO/CTAB at 0.510 mV. A simple procedure for the synthesis of ZnO particles with improved photo(electro)catalytic properties was established and it was found that even a small amount of CTAB used during processing of ZnO increases the surface-to-bulk defect ratio. Optimization of the surface-to-bulk defect ratio in ZnO materials enables increase of the absorption capacity for visible light, rendering of the recombination rate of the photogenerated pair, as well as increase of both the photocurrent density and photoconversion efficiency.

Solid-phase extraction of multi-class pharmaceuticals from environmental water samples onto modified multi-walled carbon nanotubes followed by LC-MS/MS.

In this paper, pristine and chemically treated multi-walled carbon nanotubes (MWCNTs) were employed as solid-phase extraction sorbents for the isolation and enrichment of multi-class pharmaceuticals from the surface water and groundwater, prior to liquid chromatography-tandem mass spectrometry analysis. Thirteen pharmaceuticals that belong to different therapeutical classes (erythromycin, azithromycin, sulfamethoxazole, diazepam, lorazepam, carbamazepine, metoprolol, bisoprolol, enalapril, cilazapril, simvastatin, clopidogrel, diclofenac) and two metabolites of metamizole (4-acetylaminoantipyrine and 4-formylaminoantipyrine) were selected for this study. The influence of chemical treatment on MWCNT surface characteristics and extraction efficiency was studied, and it was shown that HCl treatment of MWCNT leads to a decrease in the amount of surface oxygen groups and at the same time favorably affects the efficiency toward extraction of selected pharmaceuticals. After the optimization of the SPE procedure, the following conditions were chosen: 50 mg of HCl-treated MCWNT as a sorbent, 100 mL of water sample at pH 6, and 15 mL of the methanol-dichloromethane mixture (1:1, v/v) as eluent. Under optimal conditions, high recoveries (79-119%), as well as low detection (0.2 to 103 ng L-1) and quantitation (0.5-345 ng L-1) limits, were obtained. The optimized method was applied to the analysis of five surface water and two groundwater samples, and three pharmaceuticals were detected, the antiepileptic drug carbamazepine and two metabolites of antipyretic metamizole.

Nanoscale zerovalent iron (nZVI) supported by natural and acid-activated sepiolites: the effect of the nZVI/support ratio on the composite properties and Cd2+ adsorption.

Natural (SEP) and partially acid-activated (AAS) sepiolites were used to prepare composites with nanoscale zerovalent iron (nZVI) at different (SEP or AAS)/nZVI ratios in order to achieve the best nZVI dispersibility and the highest adsorption capacity for Cd2+. Despite the higher surface area and pore volume of AAS, better nZVI dispersibility was achieved by using SEP as the support. On the other hand, a lower oxidation degree was achieved during the synthesis using AAS. X-ray photoelectron spectroscopy (XPS) analysis of the composite with the best nZVI dispersibility, before and after Cd2+ adsorption, confirmed that the surface of the nZVI was composed of oxidized iron species. Metallic iron was not present on the surface, but it was detected in the subsurface region after sputtering. The content of zerovalent iron decreased after Cd2+ adsorption as a result of iron oxidation during Cd2+ adsorption. The XPS depth profile showed that cadmium was present not only at the surface of the composite but also in the subsurface region. The adsorption isotherms for Cd2+ confirmed that the presence of SEP and AAS decreased the agglomeration of the nZVI particles in comparison to the pure nZVI, which provided a higher adsorption capacity. The results showed that the prevention of both aggregation and oxidation during the synthesis was necessary for obtaining an SEP/AAS-nZVI composite with a high adsorption capacity, but oxidation during adsorption was beneficial for Cd2+ removal. The formation of strong bonds between Cd2+ and the adsorbents sites of different energy until monolayer formation was proposed according to modeling of the adsorption isotherms.

Influence of alkali cation on the mechanical properties and durability of fly ash based geopolymers.

This research has provided information about the influence of alkali cations (Na+ and K+) on the mechanical properties and durability of fly ash based geopolymers. The results have shown that alkali cations have a strong influence on the mechanical properties of fly ash based geopolymers. K-geopolymers generally reach a higher value of compressive strength in comparison to Na- geopolymers. On the other hand, microstructure and phase composition of fly ash based geopolymers are not influenced by the nature of alkali cations. The ratio of main gel structure forming elements is practically not affected by the nature of alkali cations. Durability of fly ash based geopolymers in different aquatic environments is greatly dependent on the choice of alkali cations. Na- geopolymers are generally more resistant in water and aggressive environments than the K-geopolymers. The best durability of fly ash based geopolymers was observed in sea water.