Nanodiamonds are a class of carbon-based nanoparticles that are rapidly gaining attention, particularly for biomedical applications, i.e., as drug carriers, for bioimaging, or as implant coatings. ...Nanodiamonds have generally been considered biocompatible with a broad variety of eukaryotic cells. We show that, depending on their surface composition, nanodiamonds kill Gram-positive and -negative bacteria rapidly and efficiently. We investigated six different types of nanodiamonds exhibiting diverse oxygen-containing surface groups that were created using standard pretreatment methods for forming nanodiamond dispersions. Our experiments suggest that the antibacterial activity of nanodiamond is linked to the presence of partially oxidized and negatively charged surfaces, specifically those containing acid anhydride groups. Furthermore, proteins were found to control the bactericidal properties of nanodiamonds by covering these surface groups, which explains the previously reported biocompatibility of nanodiamonds. Our findings describe the discovery of an exciting property of partially oxidized nanodiamonds as a potent antibacterial agent.
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IJS, KILJ, NUK, PNG, UL, UM
Surface functionalization has become of paramount importance and is considered a fundamental tool for the development and design of countless devices and engineered systems for key technological ...areas in biomedical, biotechnological and environmental applications. In this review, surface functionalization strategies for alumina, zirconia, titania, silica, iron oxide and calcium phosphate are presented and discussed. These materials have become particularly important concerning the aforementioned applications, being not only of great academic, but also of steadily increasing human and commercial, interest. In this review, special emphasis is given to their use as biomaterials, biosensors, biological targets, drug delivery systems, implants, chromatographic supports for biomolecule purification and analysis, and adsorbents for toxic substances and pollutants. The objective of this review is to provide a broad picture of the enormous possibilities offered by surface functionalization and to identify particular challenges regarding surface analysis and characterization.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Immobilizing microorganisms inside 3D printed semi-permeable substrates can be desirable for biotechnological processes since it simplifies product separation and purification, reducing costs, and ...processing time. To this end, we developed a strategy for synthesizing a feedstock suitable for 3D bioprinting of mechanically rigid and insoluble materials with embedded living bacteria. The processing route is based on a highly particle-filled alumina/chitosan nanocomposite gel which is reinforced by (a) electrostatic interactions with alginate and (b) covalent binding between the chitosan molecules with the mild gelation agent genipin. To analyze network formation and material properties, we characterized the rheological properties and printability of the feedstock gel. Stability measurements showed that the genipin-crosslinked chitosan/alginate/alumina gels did not dissolve in PBS, NaOH, or HCl after 60 days of incubation. Alginate-containing gels also showed less swelling in water than gels without alginate. Furthermore,
E. coli
bacteria were embedded in the nanocomposites and we analyzed the influence of the individual bioink components as well as of the printing process on bacterial viability. Here, the addition of alginate was necessary to maintain the effective viability of the embedded bacteria, while samples without alginate showed no bacterial viability. The experimental results demonstrate the potential of this approach for producing macroscopic bioactive materials with complex 3D geometries as a platform for novel applications in bioprocessing.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In this study, we present Janus nanoparticles that are designed for attaching to a eukaryotic cell surface with minimal cell uptake. This contrasts the rapid uptake
via
various endocytosis pathways ...that non-passivated isotropic particles usually encounter. Firmly attaching nanoparticles onto cell surfaces for extended periods of time can be a powerful new strategy to employ functional properties of nanoparticles for non-invasive interrogation and manipulation of biological systems. To this end, we synthesized rhodamine-doped silica (SiO
2
) nanoparticles functionalized with 1,2-distearoyl-
sn-glycero
-3-phosphoethanolamine (DSPE) on one hemisphere of the nanoparticle surface and high-molecular-weight long-chain poly(ethylene glycol) on the other one using the wax-Pickering emulsion technique. Nanoparticle localization was studied with NIH 3T3 rat fibroblasts
in vitro
. In these studies, the Janus nanoparticles adhered to the cell surface and, in contrast to isotropic control particles, only negligible uptake into the cells was observed, even after 24 h of incubation. In order to characterize the potential endocytosis pathway involved in the uptake of the Janus nanoparticles in more detail, fibroblasts and nanoparticles were incubated in the presence or absence of different endocytosis inhibitors. Our findings indicate that the Janus particles are not affected by caveolae- and receptor-mediated endocytosis and the prolonged attachment of the Janus nanoparticles is most likely the result of an incomplete macropinocytosis process. Consequently, by design, these Janus nanoparticles have the potential to firmly anchor onto cell surfaces for extended periods of time and might be utilized in various biotechnological and biomedical applications like cell surface tagging, magnetic manipulation of the cell membrane or non-invasive drug and gene delivery.
DSPE/PEG-coated Janus nanoparticles firmly anchor onto cell surfaces by a process that involves incomplete macropinocytosis.
Applications such as filtration require not only control over the pore structure but also over properties like surface characteristics and mechanical strength. The addition of filler particles to ...solution based freeze casting of preceramic polymers combines the flexibilities of freeze casting and preceramic polymers. Alumina platelets, silica spheres and preceramic filler particles with different compositions were frozen in solution based freeze casting of preceramic polymers with cyclohexane as solvent. Methyl- and methyl-phenyl polysiloxanes as well as (3-aminopropyl)triethoxysilane were used as precursors and cross-linking agent, respectively. The compressive strength increases by factors of up to 1.9 (25 vol% preceramic filler) due to enhanced isotropy of the dendritic pore structure. At lower concentrations (1.7 vol%), alumina platelets are more effective in strengthening than spherical particles. In dependence on the composition of the preceramic filler, BET surface area and the ratio of vapor uptake between water and heptane change by factors of up to 1.19 and 16, respectively. Calculations according to a linear rule of mixture fit very well with the experimental data. In summary, the versatile approach to add differing filler particles to solution based freeze casting allows for tailoring the pore structure as well as surface characteristics of macroporous monolithic samples.
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•Addition of preceramic and ceramic fillers overcomes limitations of solution based freeze-casting of polysiloxanes.•Enhanced isotropy of pore structure increases the compressive strength by factors of up to 1.9.•Different chemical compositions of filler particles allow for altering the BET surface area from 276.4-535.2 m2g-1.•Ratio of water to heptane uptake as a measure of hydrophilicity can be adjusted in a range from 0.13-2.86.•Linear rule of mixture precisely predicts hydrophilicity and BET surface area and allows design of properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Asymmetric porous SiOC membranes with different pore characteristic and membrane morphology were produced for the first time by adapting the phase inversion tape casting technique to the ...polymer-derived ceramic route. Polymethyl siloxane (MK) was used as a ceramic precursor. The produced tapes were pyrolyzed under N2 atmosphere. The structure and surface characteristics were tailored by changing the pyrolysis temperatures (600 and 1000°C), polyvinylpyrrolidone and solid loading. Scanning electron microscopy analysis revealed the asymmetric morphology composed by a thin skin-layer (average pore size <2μm) and a sponge-like support. The differences in membranes porosity (33–47%) and overall pore size distribution (1–10μm) can be controlled by adjusting the slurry composition. The incorporation of particles improved the slurry processability, enhanced the mechanical flexural resistance of the membrane (20–48MPa), and reduced the average pore size. Higher mechanical strengths and enhanced hydrophilic character are associated with higher pyrolysis temperatures (ceramization process). The water permeation of membranes pyrolyzed at 1000°C were assessed in a dead-end configuration device under different pressures (1–3bar). The obtained water permeation fluxes (6–55m3/m2·h, at 3bar) indicates the advantages of the asymmetric structure which minimizes mass transport limitations.
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•Porous SiOC membranes were produced by adapting the phase inversion technique to the polymer-derived ceramic route.•The open porosity (33–47%) and overall pore size distribution (1–10μm) was tailored according to the slurry composition.•The increase in pyrolysis temperature from 600°C to 1000°C enhanced the hydrophilic character of the membranes.•Higher pyrolysis temperature led to improved mechanical resistance (6–13 to 20–48MPa).•Asymmetric membranes presented a 10-fold improved permeation performance when compared to their symmetric counterpart.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Experiments are conceptualized to collect specific acoustic emission signals of different damage mechanisms by evaluating composite constituents separately.•The collected dataset is ...used to train a supervised machine learning classification model with accuracy of up to 88%•Signals of a composite tensile test are classified giving information regarding location, time, frequency and intensity of each damage type.•This approach can be applied to other materials to build a library containing characteristic features of different damage mechanisms.
Acoustic emission (AE) is a well-established technique for in-situ damage analysis of composite materials. The main challenge, however, is to be able to correlate the measured AE signals with their respective damage mechanism sources. Hence, an innovative approach to classify AE signals based on supervised machine learning is presented in this work. At first, the constituents of a composite (fiber, matrix and interface) are characterized separately and fingerprint information regarding the characteristic AE features of each damage mechanism is gathered. This dataset is then used to train a model based on the k-nearest neighbors algorithm. Model accuracy is calculated to be 88%. Subsequently, AE signals measured during tensile tests of commercial composites are classified by the trained model. The analysis provides important information regarding location, time, frequency and intensity of each damage mechanism. Matrix cracking and fiber debonding are the most frequent damage mechanisms representing around 40% and 20% of the measured AE hits. Nevertheless, fiber breakage is the mechanism that dissipates the most AE energy (40%) for the studied composite. Furthermore, the presented method can also be applied together with other techniques like computer tomography, delivering a powerful approach to understand different multi-phase materials.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In the present work, a high surface area SiC(O)‐based ceramic powder was synthesized upon thermal transformation of a polymer‐derived macromolecular precursor, which was obtained by the chemical ...modification of a allylhyldrido polycarbosilane with poly(ethylene glycol) methaacrylate under argon environment. The pyrolysis of developed precursor led to the formation of amorphous and high surface area SiC(O)‐based ceramic powder with in situ generated micro/meso‐porosity. The specific surface area of the obtained powders depends on the processing temperature. It decreases from 363 to 122 m2/g as the pyrolysis temperature increases from 600 to 1200°C, respectively. Furthermore the promising samples were fabricated using pressing technique, which led to crack‐free SiC(O) monoliths on subsquent heat treatment. The present study also emphasizes the potential of produced SiC(O) ceramic powder to support NiO catalyst. The impregnation method were used to produce high surface area NiO@SiC(O) ceramic powder (NiO as a catalyst; SiC(O) as a catalyst support) for further catalytic applications. Interestingly, the distribution of the NiO was shown to strongly depend on the oxygen content present in the SiC(O) matrix. Thus, larger oxygen contents induce homogeneously distributed flower‐like NiO catalyst onto SiC(O).
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
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•Tert-butyl alcohol-cyclohexane phase-diagram reveals an eutectic point at around −24 °C.•Honeycomb-like pore structure templated by tert-butyl alcohol-cyclohexane mixture.•Pore sizes ...range from 11-57 µm depending on the solvents and freezing condition.•Compressive strengths reach 5-39 MPa depending on the solvents.•Isothermal wicking rate can be adjusted from fast to slow depending on pore structure.
Macroporous SiOC monoliths were prepared by solution-based freeze-casting of a polymethyl siloxane using cyclohexane (CH) and tert-butyl alcohol (TBA) as a novel template media. Samples with TBA amounts of 100, 90, 80 and 0 wt% were stable during preparation at −20 °C. Using TBA or CH creates prismatic or dendritic pore structures, respectively, while a mixture of these solvents generates honeycomb-like pore structures. A constant freezing rate produces homogeneous pore window sizes while freezing with velocity gradients produces inhomogeneous pore window sizes. Variations in the amount of TBA led to pore sizes between 11 and 57 µm and consequently to water permeabilities of 4.4 × 10-13 to 1.4 × 10-11m2. The dendritic pore structure has the highest compressive strength (39 MPa) due to its smallest pore sizes (16–20 µm) and secondary dendrites. In wicking experiments, these structural properties and the lowest permeability resulted in the slowest wicking rate in contrast to prismatic pore structures with the biggest pore sizes (31–57 µm) and highest permeability. Honeycomb-like pore structures allow medium wicking rates with the pore size being the main influencing factor. The adjustment of the solvent allows tailoring the mass transport and mechanical properties as key elements in capillary transport applications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this study, we present hydrophobic yttria-stabilized zirconia capillary membranes conditioned for virus filtration. These macroporous ceramic filters (d50 = 150 nm) efficiently extract viruses ...regardless of their surface charge with high throughput rates. For hydrophobic functionalization of the ceramic membranes we used two different silanes, n-hexyltriethoxysilane (HTS, C6-chain) and n-octyltriethoxysilane (OTS, C8-chain), in three different molarities. The virus retention of the membranes is tested in dead-end mode by intracapillary virus feeding using two small bacteriophages as model species: MS2 and PhiX174. Virus retention increases most strongly for hydrophobic capillaries functionalized with 0.05 M OTS, showing a virtually complete retention with log-reduction values (LRVs) of ~ 9 for both bacteriophages compared to the non-functionalized membrane with LRVs of 0.3 ± 0.1 for MS2 and 3.4 ± 0.2 for PhiX174. The functionalized membranes allow a high membrane flux of ~ 150 L/(m2hbar), with throughput rates up to ~ 400 L/(m2 h) while maintaining high filtration efficiency. Even under varying feed conditions using only mono- or divalent salt ions or pH values ranging from 3 to 9, retention capacities of the capillary membranes are high. Accordingly, such hydrophobic ceramic membranes offer a versatile alternative to conventional polymeric membranes for virus removal with greatly improved membrane flux.
•Virus retention can be increased with hydrophobic ceramic membranes.•Virus retention increases the most for capillaries silanized with 0.05 M noctyltriethoxysilane.•The silane is stably bonded to the surface over a period of at least 3 weeks even under flow conditions.•The membranes allow a high membrane flux of ~150 L/(m2 h bar), with throughput rates up to ~ 400 L/(m2 h).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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