Search Results (11)

Pulsed laser ablation in liquids is one of the most versatile and widespread techniques for the easy synthesis of different types of nanoparticles with controllable properties. A huge amount of energy compressed into one pulse that is directed onto a solid target leads to the ejection of materials into surrounding liquid. However, the precision of the focus of laser irradiation can play a crucial role in the synthesis of nanomaterials and, hence, significantly affect their physico-chemical properties. In this paper, we investigated the influence of the focus position of the laser spot on the optical properties of single- and double-element composite silicon/gold nanoparticles, as well as on their structure and chemical composition. Deepening of the focus to 0.5 mm inside the bulk material led to better chemical stability of the colloidal solutions and increased the particle and mass concentrations of the generated nanoparticles. This larger amount of materials led to a stronger absorbance, and resulted in slightly better photoluminescence excitation efficiencies for all nanostructures. Silicon-based nanoparticles had a remarkable photoluminescence peak at ~430 nm upon xenon lamp excitation, which was the most pronounced for pure silicon nanoparticles synthesized at the F+0.5 focus position. This position also led to the best laser-induced heating (~0.85 °C/min) of the colloidal solutions. All nanocomposites revealed amorphous silicon structures with some Si(111) and Au(111), suggesting the formation of gold silicide with different stoichiometries. The observed findings can help in choosing appropriate experimental conditions to achieve the best performance of laser-synthesized colloidal solutions of composite silicon/gold nanostructures. Full article

Ultrafast laser processing possesses unique outlooks for the synthesis of novel nanoarchitectures and their further applications in the field of life science. It allows not only the formation of multi-element nanostructures with tuneable performance but also provides various non-invasive laser-stimulated modalities. In this work, we employed ultrafast laser processing for the manufacturing of silicon–gold nanocomposites (Si/Au NCs) with the Au mass fraction variable from 15% (0.5 min ablation time) to 79% (10 min) which increased their plasmonic efficiency by six times and narrowed the bandgap from 1.55 eV to 1.23 eV. These nanostructures demonstrated a considerable fs laser-stimulated hyperthermia with a Au-dependent heating efficiency (~10–20 °C). The prepared surfactant-free colloidal solutions showed good chemical stability with a decrease (i) of zeta (ξ) potential (from −46 mV to −30 mV) and (ii) of the hydrodynamic size of the nanoparticles (from 104 nm to 52 nm) due to the increase in the laser ablation time from 0.5 min to 10 min. The electrical conductivity of NCs revealed a minimum value (~1.53 µS/cm) at 2 min ablation time while their increasing concentration was saturated (~10¹² NPs/mL) at 7 min ablation duration. The formed NCs demonstrated a polycrystalline Au nature regardless of the laser ablation time accompanied with the coexistence of oxidized Au and oxidized Si as well as gold silicide phases at a shorter laser ablation time (<1 min) and the formation of a pristine Au at a longer irradiation. Our findings demonstrate the merged employment of ultrafast laser processing for the design of multi-element NCs with tuneable properties reveal efficient composition-sensitive photo-thermal therapy modality. Full article

Infant feces and breast milk are sources of lactic acid bacteria with interesting functional and technological properties. Therefore, we focused on the isolation and characterization of new potential probiotic strains from infant feces and breast milk. Nine strains were identified based on 16S rRNA sequences of Lacticaseibacillus rhamnosus, Limosilactobacillus reuteri, and Lactobacillus gasseri. Subsequently, these isolates were evaluated for their safety (antibiotic resistance, hemolytic, and enzymatic activity) and functional properties (gastrointestinal condition tolerance, hydrophobicity, auto-aggregation, adhesion to Caco-2/HT-29 cell lines, antimicrobial and antioxidant properties, and the production of exopolysaccharides). All the isolates were non-hemolytic and resistant to streptomycin, kanamycin, and vancomycin. They also demonstrated antimicrobial activity against five selected pathogens (Staphylococcus aureus, Bacillus cereus, Escherichia coli, Salmonella sp., and Enterococcus faecalis) and the production of exopolysaccharides. Isolates Lacticaseibacillus rhamnosus S1F and S6C together with Lactobacillus gasseri M8C showed the highest ability to survive 3.0 g/L of bile salts and a good adhesion property, which is important for gastrointestinal tract (GIT) colonization or the inhibition of pathogens. Following in vivo characterization, three strains S1F and S6C from infant feces, and M6C from breast milk, showed probiotic properties with potential applications in the food industry. Full article

The unicellular green microalga Dunaliella is a potential source of a wide range of nutritionally important compounds applicable to the food industry. The aim of this study was to assess the effect of Dunaliella salina dried biomass on the growth and adherence of 10 strains of Lactobacillus, Lacticaseibacillus, and Bifidobacterium. The immunomodulatory, antioxidant, and cytotoxic effects of D. salina on human peripheral mononuclear cells and simulated intestinal epithelial cell lines Caco-2 and HT-29 were evaluated. Furthermore, the hypocholesterolemic effects of the microalgae on lipid metabolism in rats fed a high-fat diet were analyzed. The addition of D. salina biomass had a positive effect on the growth of nine out of 10 probiotics and promoted the adherence of three bifidobacteria strains to human cell lines. The antioxidant and immunomodulatory properties of D. salina were concentration-dependent. The inflammatory cytokines (TNF-α and IL-6) were significantly increased following Dunaliella stimulation at the lowest concentration (0.5% w/v). Eight week supplementation of D. salina to the diet of hypercholesteromic rats significantly decreased the serum concentrations of LDL-C, VLDL, IDL-B, and IDL-C. D. salina is not cytotoxic in intestinal cell models; it promotes adherence of selected bifidobacteria, it affords immunomodulatory and antioxidant effects, and its addition to diets may help decrease atherosclerosis risk factors. Full article

The microalga Chlorella and strains of Bifidobacterium have been used in human or animal food supplements for decades because of their positive health effects. The presented study assessed different properties of C. vulgaris and its combination with bifidobacteria with the aim to develop new functional foods. The growth of four bifidobacteria strains in milk and whey supplemented with 1.0% (w/v) C. vulgaris and the immunomodulatory effects of aqueous Chlorella solutions (0.5%, 1.0%, and 3.0%) on human peripheral mononuclear cells were evaluated. Furthermore, synergistic effects on lipid metabolism of rats fed a high-fat diet with Chlorella and B. animalis subsp. lactis BB-12^® were analysed. Chlorella had a positive growth-promoting effect on the tested bifidobacteria (p < 0.05), and significantly increased the secretion of inflammatory cytokines (tumor necrosis factor-α, interleukin-10, and interleukin-6), depending on the concentration of Chlorella (p < 0.05). After 8 weeks, significant synergistic effects of Chlorella and bifidobacteria on triglyceride levels in rat heart, liver, and serum were observed (p < 0.05). These results demonstrate that various combinations of Chlorella and bifidobacteria have significant potential for the development of new fermented products, dependent on the algal species, probiotic strain, application form, and concentrations for acceptable sensory quality for consumers. Full article

The market for new functional foods and food supplements is rapidly evolving, with a current emphasis on using natural sources. Algae, probiotics, and colostrum are rich sources of nutrients and bioactive compounds with positive effects on human and animal health. To determine the potential for developing new functional foods combining these components, we evaluated their synergistic effects. We assessed the growth of selected bifidobacteria in a medium supplemented with Chlorella vulgaris and its immunomodulatory and cytotoxic effects on the human peripheral mononuclear cells and colon cancer cell lines Caco-2 and HT29. The hypocholesterolemic effects of Chlorella powder and bovine colostrum fermented by Bifidobacterium animalis subsp. lactis BB12^® on lipid metabolism in rats fed a high-fat diet were also determined. Chlorella addition promoted Bifidobacteria growth, with significantly increased inflammatory cytokine (TNF-α and IL-6) levels following 1.0% (w/v) Chlorella stimulation. Rats fed diets containing fermented colostrum with 0.5% (w/v) added Chlorella powder exhibited significantly decreased triglyceride, very low-density lipoprotein, and alanine and aspartate aminotransferase levels, compared to those of the control group. These results support that C. vulgaris is not cytotoxic in intestinal cell models and affords prebiotic and immunomodulatory effects, as well as synergistic triglyceride-lowering effects with bovine colostrum and B. animalis subsp. lactis BB-12. Full article

The selenium (Se) enrichment of yeasts and lactic acid bacteria (LAB) has recently emerged as a novel concept; the individual health effects of these beneficial microorganisms are combined by supplying the essential micronutrient Se in a more bioavailable and less toxic form. This study investigated the bioavailability of Se in the strains Enterococcus faecium CCDM 922A (EF) and Streptococcus thermophilus CCDM 144 (ST) and their respective Se-enriched forms, SeEF and SeST, in a CD (SD-Sprague Dawley) IGS rat model. Se-enriched LAB administration resulted in higher Se concentrations in the liver and kidneys of rats, where selenocystine was the prevalent Se species. The administration of both Se-enriched strains improved the antioxidant status of the animals. The effect of the diet was more pronounced in the heart tissue, where a lower glutathione reductase content was observed, irrespective of the Se fortification in LAB. Interestingly, rats fed diets with EF and SeEF had higher glutathione reductase activity. Reduced concentrations of serum malondialdehyde were noted following Se supplementation. Diets containing Se-enriched strains showed no macroscopic effects on the liver, kidneys, heart, and brain and had no apparent influence on the basic parameters of the lipid metabolism. Both the strains tested herein showed potential for further applications as promising sources of organically bound Se and Se nanoparticles. Full article

Unconventional wire electrical discharge machining technology (WEDM) is a key machining process, especially for machining newly emerging materials, as there are almost no restrictions (only at least minimal electrical conductivity) in terms of demands on the mechanical properties of the workpiece or the need to develop new tool geometry. This study is the first to present an analysis of the machinability of newly developed high entropy alloys (HEAs), namely FeCoCrMnNi and FeCoCrMnNiC_0.2, using WEDM. The aim of this study was to find the optimal setting of machine parameters for the efficient production of parts with the required surface quality without defects. For this reason, an extensive design of experiments consisting of 66 rounds was performed, which took into account the influence of five input factors in the form of pulse off time, gap voltage, discharge current, pulse on time, and wire speed on cutting speed and the quality of the machined surface and its subsurface layer. The analysis of topography, morphology, subsurface layers, chemical composition analysis (EDX), and lamella analysis using a transmission electron microscope (TEM) were performed. An optimal setting of the machine parameters was found, which enables machining of FeCoCrMnNi and FeCoCrMnNiC_0.2 with the required surface quality without defects. Full article

Over the past decade, the use of bovine colostrum and its bioactive components as the basis of functional food and dietary supplements for humans has substantially increased. However, for developing new products enriched with probiotics and bovine colostrum, the influence of colostrum composition on the growth promotion of bacteria still needs to be tested. Therefore, we decided to study the influence of bovine colostrum chemical and mineral composition as well as the content of bioactive compounds (immunoglobulins, lactoferrin, lactoperoxidase) on the growth of ten selected strains from genera Lactobacillus, Lacticaseibacillus, Bifidobacterium, and Enterococcus. After 24 h of fermentation, the growth was assessed based on lactic and acetic acids production evaluated using isotachophoresis, bacterial counts determined by the agar plate method, and change of pH. The production of acids and bacterial counts were significantly (P<0.05) different between selected genera. The change of bacterial counts was correlated with pH, but the correlation between growth and bovine colostrum composition was not proven. The highest growth and production of lactic acid was observed after the fermentation of bovine colostrum by the strains Enterococcus faecium CCDM 922A and CCDM 945. Full article

Selenized lactic acid bacteria (LAB) represent potentially safe and effective sources of selenium (Se), essential for human health, as lactic acid fermentation improves Se bioavailability and reduces its toxicity. LAB are generally recognized as safe (GRAS) and widely used in fermented dairy products. To facilitate selenized LAB implementation as a functional food, we developed and characterized new Se-enriched strains based on the food industry commercial strains Streptococcus thermophilus CCDM 144 and Enterococcus faecium CCDM 922A as representatives of two LAB genera. We evaluated Se bioaccumulation capacity, Se biotransformation and growth ability in the presence of different sodium selenite concentrations (0–50 mg/L), and antioxidant properties (2, 2-diphenyl-1-picrylhydrazyl (DPPH) method) and cell surface hydrophobicity between Se-enriched and parental strains in vitro. Sodium selenite addition did not negatively influence growth of either strain; thus, 50 mg/L was chosen as the optimal concentration based on strain accumulation capacity. Selenization improved the antioxidant properties of both strains and significantly increased their cell surface hydrophobicity (p < 0.05). To our knowledge, this represents the first report of Se-enriched strain hydrophobicity as well as the first on Se speciation in families Enterococcaceae and Streptococcaceae. Moreover, both tested strains demonstrated good potential for Se-enrichment, providing a foundation for further in vitro and in vivo studies to confirm the suitability of these Se-enriched strains for industrial applications. Full article

One of the prevailing problems for materials produced by powder metallurgy is contamination from various sources. This work deals with the influence of process parameters and presence of process control agents (PCA) on the contamination level of materials produced by means of mechanical alloying (MA) technology, densified with spark plasma sintering (SPS). The equiatomic CoCrFeNi high-entropy alloy (HEA) was manufactured by the said methodology. For clear comparison, the 316L austenitic steel powder was milled and densified with identical conditions as a reference material. Both materials were milled in argon and nitrogen atmospheres for various times from 5 to 30 h. Chemical analysis of contamination by carbon, oxygen, and nitrogen within the powder and bulk materials was carried out using combustion analyzers. The microstructural analysis of powders and bulk samples was carried out using scanning electron microscopy (SEM) with focus on contaminant phases. The results show that carbon contamination increases with milling time. It is caused by wear of milling vial and balls made from high-carbon steels. Increase of carbon content within consolidation using SPS was also observed. The oxygen contamination also increases with milling time. It is more pronounced in the CoCrFeNi alloy due to higher oxidation of powder surfaces prior to milling. Milling of powders using nitrogen atmosphere also causes an increase of nitrogen content in both HEA and AISI 316L. The use of PCA (ethanol) during milling even for a short time (30 min) causes significant increase of carbon and oxygen contamination. The ways to decrease contamination are discussed in the paper. Full article