Search

Staphylococcus aureus biofilm-associated infections are a common complication in modern medicine. Due to inherent resilience of biofilms to antibiotics and the rising number of antibiotic-resistant bacterial strains, new treatment options are required. For this purpose, ultrapure, spherical silver–gold-alloy nanoparticles with homogenous elemental distribution were synthesized by laser ablation in liquids and analyzed for their antibacterial activity on different stages of S. aureus biofilm formation as well as for different viability parameters. First, the effect of nanoparticles against planktonic bacteria was tested with metabolic activity measurements. Next, nanoparticles were incubated with differently matured S. aureus biofilms, which were then analyzed by metabolic activity measurements and three dimensional live/dead fluorescent staining to determine biofilm volume and membrane integrity. It could be shown that AgAu NPs exhibit antibacterial properties against planktonic bacteria but also against early-stage and even mature biofilms, with a complete diffusion through the biofilm matrix. Furthermore, AgAu NPs primarily targeted metabolic activity, to a smaller extend membrane integrity, but not the biofilm volume. Additional molecular analyses using qRT-PCR confirmed the influence on different metabolic pathways, like glycolysis, stress response and biofilm formation. As this shows clear similarities to the mechanism of pure silver ions, the results strengthen silver ions to be the major antibacterial agent of the synthesized nanoparticles. In summary, the results of this study provide initial evidence of promising anti-biofilm characteristics of silver–gold-alloy nanoparticles and support the importance of further translation-oriented analyses in the future. [ABSTRACT FROM AUTHOR]

High entropy metallic glass nanoparticles (HEMG NPs) are very promising materials for energy conversion due to the wide tuning possibilities of electrochemical potentials offered by their multimetallic character combined with an amorphous structure. Up until now, the generation of these HEMG NPs involved tedious synthesis procedures where the generated particles were only available on highly specialized supports, which limited their widespread use. Hence, more flexible synthetic approaches to obtain colloidal HEMG NPs for applications in energy conversion and storage are highly desirable. We utilized pulsed laser ablation of bulk high entropy alloy targets in acetonitrile to generate colloidal carbon-coated CrCoFeNiMn and CrCoFeNiMnMo HEMG NPs. An in-depth analysis of the structure and elemental distribution of the obtained nanoparticles down to single-particle levels using advanced transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) methods revealed amorphous quinary and senary alloy phases with slight manganese oxide/hydroxide surface segregation, which were stabilized within graphitic shells. Studies on the catalytic activity of the corresponding carbon-HEMG NPs during oxygen evolution and oxygen reduction reactions revealed an elevated activity upon the incorporation of moderate amounts of Mo into the amorphous alloy, probably due to the defect generation by atomic size mismatch. Furthermore, we demonstrate the superiority of these carbon-HEMG NPs over their crystalline analogies and highlight the suitability of these amorphous multi-elemental NPs in electrocatalytic energy conversion. [ABSTRACT FROM AUTHOR]

Bimetallic nanoparticles are often superior candidates for a wide range of technological and biomedical applications owing to their enhanced catalytic, optical, and magnetic properties, which are often better than their monometallic counterparts. Most of their properties strongly depend on their chemical composition, crystallographic structure, and phase distribution. However, little is known of how their crystal structure, on the nanoscale, transforms over time at elevated temperatures, even though this knowledge is highly relevant in case nanoparticles are used in, e.g., high-temperature catalysis. Au-Fe is a promising bimetallic system where the low-cost and magnetic Fe is combined with catalytically active and plasmonic Au. Here, we report on the in situ temporal evolution of the crystalline ordering in Au-Fe nanoparticles, obtained from a modern laser ablation in liquids synthesis. Our in-depth analysis, complemented by dedicated atomistic simulations, includes a detailed structural characterization by X-ray diffraction and transmission electron microscopy as well as atom probe tomography to reveal elemental distributions down to a single atom resolution. We show that the Au-Fe nanoparticles initially exhibit highly complex internal nested nanostructures with a wide range of compositions, phase distributions, and size-depended microstrains. The elevated temperature induces a diffusion-controlled recrystallization and phase merging, resulting in the formation of a single face-centered-cubic ultrastructure in contact with a body-centered cubic phase, which demonstrates the metastability of these structures. Uncovering these unique nanostructures with nested features could be highly attractive from a fundamental viewpoint as they could give further insights into the nanoparticle formation mechanism under non-equilibrium conditions. Furthermore, the in situ evaluation of the crystal structure changes upon heating is potentially relevant for high-temperature process utilization of bimetallic nanoparticles, e.g., during catalysis. [ABSTRACT FROM AUTHOR]

Wound healing is a complex orchestration of processes involving cell proliferation, migration, differentiation, anabolism, and catabolism in order to restore skin continuity. Within these processes, elements such as metallic ions are involved due to their implications in cell behavior and enzymatic activity regulation. This study analyzed the kinetics of zinc, iron, copper and magnesium concentrations in a full thickness open wound rat model over 14 days. We made wounds with a diameter of 6 mm on the back of Lewis rats and let them heal naturally prior to analysis by histology and inductively coupled plasma mass spectrometry analysis. Histological and immunofluorescence analysis confirmed an inflammation phase until 7 days, epithelial proliferation phase from 16 h to 10 days, and remodeling phase from 7 days onward. These defined phases were correlated with the measured metal element kinetics. Zinc concentrations showed an inverted parabolic progression between 30.4 and a maximum of 39.9 μg/g dry weight. Magnesium values had a similar pattern between 283 and 499 μg/g dry weight. Copper concentrations, on the other hand, followed an inverted sigmoid trend with a decrease from 9.8 to 1.5 μg/g dry weight. Iron had a slight decrease in concentration for 24 h followed by an increase to a maximum of 466 μg/g dry weight. In conclusion, zinc, iron, and copper, even though differing in their total mass within the wound, exhibited concentration curve transitions at day 3. Interestingly, this time point correlates with the maximum proliferating keratinocyte rate during the proliferation phase. [ABSTRACT FROM AUTHOR]

Alginate is a widely used hydrogel in tissue engineering owing to its simple and non-cytotoxic gelation process, ease of use, and abundance. However, unlike hydrogels derived from mammalian sources such as collagen, alginate does not contain cell adhesion ligands. Here, we present a novel laser ablation technique for the in situ embedding of gold and iron nanoparticles into hydrogels. We hypothesized that integration of metal nanoparticles in alginate could serve as an alternative material because of its chemical biofunctionalization ability (coupling of RGD ligands) to favor cell adhesion. Cytocompatibility and biofunctionality of the gels were assessed by cell culture experiments using fibroblasts and endothelial cells. Nanoparticles with an average particle size of 3 nm (gold) and 6 nm (iron) were generated and stably maintained in alginate for up to 6 months. Using an extrusion system, several centimeter-long alginate tubes with an outer diameter of approximately 3 mm and a wall thickness of approximately 150 μm were manufactured. Confocal microscopy revealed homogeneously distributed nanoparticle agglomerates over the entire tube volume. Endothelial cells seeded on iron-loaded gels showed significantly higher viability and an increased degree of spreading, and the number of attached cells was also elevated in comparison to the control and gold-loaded alginates. We conclude that laser-based in situ integration of iron nanoparticles (⩽0.01 wt.%) in alginate is a straightforward method to generate composite materials that favor the adhesion of endothelial cells. In addition, we show that nanoparticle integration does not impair the alginate's gelation and 3D biofabrication properties. [ABSTRACT FROM AUTHOR]

Over the last two decades, more and more applications of sophisticated sensor technology have been described in the literature on upstreaming and downstreaming for biotechnological processes (Middendorf et al. J Biotechnol 31:395-403, ; Lausch et al. J Chromatogr A 654:190-195, ; Scheper et al. Ann NY Acad Sci 506:431-445, ), in order to improve the quality and stability of these processes. Generally, biotechnological processes consist of complex three-phase systems-the cells (solid phase) are suspended in medium (liquid phase) and will be streamed by a gas phase. The chemical analysis of such processes has to observe all three phases. Furthermore, the bioanalytical processes used must monitor physical process values (e.g. temperature, shear force), chemical process values (e.g. pH), and biological process values (metabolic state of cell, morphology). In particular, for monitoring and estimation of relevant biological process variables, image-based inline sensors are used increasingly. Of special interest are sensors which can be installed in a bioreactor as sensor probes (e.g. pH probe). The cultivation medium is directly monitored in the process without any need for withdrawal of samples or bypassing. Important variables for the control of such processes are cell count, cell-size distribution (CSD), and the morphology of cells (Höpfner et al. Bioprocess Biosyst Eng 33:247-256, ). A major impetus for the development of these image-based techniques is the process analytical technology (PAT) initiative of the US Food and Drug Administration (FDA) (Scheper et al. Anal Chim Acta 163:111-118, ; Reardon and Scheper ; Schügerl et al. Trends Biotechnol 4:11-15, ). This contribution gives an overview of non-invasive, image-based, in-situ systems and their applications. The main focus is directed at the wide application area of in-situ microscopes. These inline image analysis systems enable the determination of indirect and direct cell variables in real time without sampling, but also have application potential in crystallization, material analysis, polymer research, and the petrochemical industry. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]