Construction of Er-doped ZnO/SiO2 composites with enhanced antimicrobial properties and analysis of antibacterial mechanism

Herein, silica carrier was used as underlying structure to prepare composite material loaded with rare earth element Er and Zn. Rare earth elements can improve antimicrobial effects of ZnO due to their specific electronic structure. Er–ZnO/SiO₂ hybrid antibacterial material was prepared through sol-gel method and its structure and morphology were characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, inductively coupled plasma emission spectroscopy and Brunauer-Emmett-Teller measurements. E. coli and S. aureus were selected as model bacteria to assess antibacterial activity of prepared hybrid material by plate coating method. Er–ZnO/SiO₂ exhibited good antibacterial activity towards E. coli and S. aureus. Increase in Er³⁺ concentration from 0.12% to 1.10% led to increase in antibacterial performance followed by subsequent decrease. Improving effect of Er relied on the molar ratio of Er doped in ZnO/SiO₂ hybrid material. The optimal sample was found to be 0.60%Er–ZnO/SiO₂, with antibacterial rates of 93.71% and 70.46% against E. coli and S. aureus, respectively. Antibacterial mechanism was assessed by fluorescence detection of reactive oxygen species. In addition, flame atomic absorption spectrometry was used to measure the amount of released Zn²⁺. Results also showed that 0.60%Er–ZnO/SiO₂ hybrid material generated more reactive oxygen species, released more Zn²⁺ ions, and had the largest surface area, which improved its antibacterial rate. Thus, Er enhanced antibacterial properties of ZnO/SiO₂, providing these composite materials with great potential as antibacterial products.     

Catalytic Wet Oxidation of H<Subscript>2</Subscript>S to Sulfur on V/MgO Catalyst

The V/MgO catalysts with different V₂O₅ loadings were prepared by impregnating MgO with aqueous vanadyl sulfate solution. All of the catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). It was observed that the H₂S removal capacity with respect to vanadia content increased up to 6 wt%, and then decreased with further increase in vanadia loading. The prepared catalysts had BET surface areas of 11.3 ~ 95.9 m²/g and surface coverages of V₂O₅ of 0.1 ~ 2.97. The surface coverage calculation of V₂O₅ suggested that a vanadia addition up to a monomolecular layer on MgO support increased the H₂S removal capacity of V/MgO, but the further increase of VO _x surface coverage rather decreased that. Raman spectroscopy showed that the small domains of Mg₃(VO₄)₂ could be present on V/MgO with less than 6 wt% vanadia loading. The crystallites of bulk Mg₃(VO₄)₂ and Mg₂(V₂O₇) became evident on V/MgO catalysts with vanadia loading above 15 wt%, which were confirmed by a XRD. The TPR experiments showed that V/MgO catalysts with the loading below 6 wt% V₂O₅ were more reducible than those above 15 wt% V₂O₅. It indicated that tetrahedrally coordinated V⁵⁺ in well-dispersed Mg₃(VO₄)₂ domains could be the active species in the H₂S wet oxidation. The XPS studies indicated that the H₂S oxidation with V/MgO could proceed from the redox mechanism (V⁵⁺ V⁴⁺) and that V³⁺ formation, deep reduction, was responsible for the deactivation of V/MgO.     

Antibacterial properties of plasma-modified and triclosan or bronopol coated polyethylene

The antibacterial properties of medical polyethylene (PE) were enhanced by coating with triclosan or bronopol and plasma immersion ion implantation (PIII). O₂ plasma was first employed to produce a more hydrophilic surface on the PE, followed by argon or hydrogen plasma treatment to enhance the coating of triclosan or bronopol onto the surface. The modified surfaces were characterized by XPS, FTIR, SEM, and contact angle measurements. The antibacterial properties were evaluated utilizing the method of plate-counting of Staphylococcus aureus (Gram positive) and Escherichia coli (Gram negative). Our experimental results show that the plasma-modified PE with triclosan exhibits excellent antibacterial properties. Even after 6 weeks, the antibacterial effects against E. coli and S. aureus remain at high levels of 99.9 and 68.4%. The plasma-modified PE with bronopol has better antibacterial performances against E. coli and S. aureus in the beginning. Afterwards, the antibacterial effects degrade relatively rapidly. Our results reveal that non-reactive argon plasma was better than reactive hydrogen plasma in improving the antibacterial properties of PE. Bacterial adhesion on the modified samples was also investigated and the number of active adhered bacteria was observed to be always low.     

Effective factor on antibacterial characteristics of Mg1−XNiXO solid solution

Mg_1−XNi_XO solid solution powder samples with different chemical compositions were prepared by heating MgO–NiO mixtures at 1300 °C for 12 h in air. From XRD measurement, all powder samples were indexed as a single phase of cubic structure, of which the diffraction peaks shifted to high-angle side with the increase of doping amount of NiO. The pH values of the solution dispersed with the powder samples decreased when the doping amount of NiO in solid solution was increased. Antibacterial activity of the powder samples was examined by colony count method. In the result, the antibacterial activity of Mg_1−XNi_XO was remarkably weaker than original MgO powders, irrespective of the kind of bacteria. In addition, it was found that the antibacterial activity of Mg_1−XNi_XO reduced with increasing the doping amount of NiO. Two factors, the generated amount of O₂⁻ and the eluted amount of Ni²⁺ ions affected the antibacterial activity of Mg_1−XNi_XO solid solution. Especially, the stability of O₂⁻ in aqueous solution is dependent on pH value. Therefore, the strength of antibacterial activity was associated with the pH values in the dispersed solution of Mg_1−XNi_XO.     

Ru Nanoparticles Entrapped in Mesopolymers for Efficient Liquid-phase Hydrogenation of Unsaturated Compounds

A chemical potential diagram of the V–Mg–O system was constructed for comparison in an in-situ experiment. A V–Mg–O catalyst used in the oxidative dehydrogenation of n-butane was prepared by the impregnation method and was characterized by in-situ X-ray diffraction (XRD). Mg₃V₂O₈ and MgO were detected on the in-situ XRD pattern under the oxygen pretreatment at 600 °C, and the in-situ XRD data under working conditions showed that Mg₃V₂O₈ is reduced to MgV₂O₄, having a cubic spinel structure with a lattice constant of a = 8.427 Å. The observed reduction of V⁵⁺ in Mg₃V₂O₈ to V³⁺ in MgV₂O₄ under the working conditions could be well understood through a chemical potential diagram.     

Catalyst Structure-Performance Relationship Identified by High-Throughput Operando Method: New Insight for Silica-Supported Vanadium Oxide for Methanol Oxidation

The reaction mechanism of methanol oxidation catalyzed by vanadium oxides on a silica support (V₂O₅/SiO₂) was investigated in a high-throughput operando reactor coupled with a Fourier transform-infrared (FT-IR) imaging system for rapid product analysis and six parallel, in situ Raman spectroscopy probes for catalyst characterization. Up to six V₂O₅/SiO₂ catalysts with different vanadium loadings (i.e., from 0 to 7%) were simultaneously monitored under identical experimental conditions. The specific Raman bands of the different catalysts in the six parallel reaction channels are quantitatively determined in this work. Under steady-state reaction conditions, the Raman intensities of C–H stretch in Si–O–CH₃ and V–O–CH₃ were extensively studied at different reaction temperatures and different vanadium loadings. For the first time, we observed enhanced Si–O–CH₃ formation on V₂O₅/SiO₂ catalysts with low vanadium loadings. We attribute this phenomenon to surface cluster edge activation. Careful comparison of the in situ Raman intensity of V–O–CH₃ on V₂O₅/SiO₂ catalysts revealed different methoxy formation mechanisms in different reaction temperature regimes.     

The impact of Nb2O5 on in-vitro bioactivity and antibacterial activity of CaF2–CaO–B2O3–P2O5–SrO glass system

This work consists of in vitro bioactivity (in SBF) and antibacterial studies (against S. aureus and E. coli bacteria) of Nb₂O₅ doped bioactive glasses. X-ray diffraction and scanning electron microscopy investigations indicated deposition of Nb-HAp (hydroxyapatite) crystalline layer on the samples after exposing to SBF. The spectroscopy investigations also indicated the deposition of HAp layer on these samples. The magnitude of HAp deposited on the glasses found to be relying on concentration of Nb₂O₅ dopant; this conclusion was drawn by determining weight loss of the glasses due to exposure to SBF and also by assessing the variation of pH of the remnant fluid as functions of Nb₂O₅content. The studies further indicated the maximal content of hydroxyapatite was deposited on the surface the glasses doped with 4.0 mol% of Nb₂O₅. The antibacterial studies (against E. coli and S. aureus bacteria) of these glasses indicated the maximal killing effect of bacteria of the samples admixed with 4.0 mol% of Nb₂O₅. This result is attributed to the occupancy of maximal fraction of Nb ions in NbO₆ structural units (confirmed by IR and Raman spectroscopic results) in this sample that paved the way for easy disintegration of the glass and to act on the bacteria. Overall, the results of bioactivity studies of Nb₂O₅ doped bioglasses indicated that the Nb₂O₅ not only enhanced bioactivity potential but also exhibited antimicrobial activity.     

Fabrication and in vitro characterization of antibacterial magneto-luminescent core-shell bioactive glass nanoparticles

When nanomaterials with antibacterial properties were sent to the infected area, it was predicted that infection and related complications could be prevented. The nanoparticles can be designed to possess magnetic and luminescence (magneto-luminescent) properties to be effectively targeted and localized at the infection foci without dispersing into the body. Simultaneously, the magneto-luminescent characteristic of particles allows visualization and confirmation of localized particles at the desired area. In this regard, there are no studies on the use of antibacterial magneto-luminescent bioactive glass for orthopedic applications and the treatment of orthopedic device-related infections. In this study, antibacterial magneto-luminescent 58S bioactive glasses were synthesized by the modified Stöber using coupled with a layer-by-layer assembly approach to possess core/shell particle morphology. SPION/Bioactive glass nanoparticles had an average size of 50 nm and displayed superparamagnetic behavior. While the saturation magnetization value (σ_s) of the undoped 58S sample was 25.32 emu/g, that of the co-doped sample (2% Eu, 2% Zn) was 21.74 emu/g; this showed that the doping slightly reduced the magnetization value. Europium (Eu) doping of SPION/Bioactive glass nanoparticles induced characteristic red emission originating from Eu emissions belonging to ⁵D₀–⁷F_J (J = 1–4) transitions and the strongest peak was at 612 nm (electric-dipole transition, ⁵D₀–⁷F₂). Color chromaticity coordinates confirmed emission in the red region. XPS spectrum revealed the existence of Eu and Zn dopant elements in 58S bioactive glass. After soaking characteristic peaks at 31.74° and 45.43° belonging to the hexagonal hydroxyapatite phase were detected in the XRD data, confirming the SEM images. 2% Eu doped SPION/Bioactive glass nanoparticles had the highest osteoblast viability up to 7 days in vitro, while doping the samples with 2% zinc did not yield bone cell viability as high as the Eu doped ones. Importantly, Eu doped SPION/Bioactive glass nanoparticles inhibited gram-positive Staphylococcus aureus (S. aureus) and gram-negative Escherichia coli (E. coli) growth up to 48 h in vitro. The results showed that Eu doping of SPION/Bioactive glass nanoparticles increased osteoblast viability and inhibited bacterial growth, while possessing superparamagnetic properties and exhibiting red luminescence.     

Corrosion behavior of Zn-incorporated antibacterial TiO2 porous coating on titanium

Incorporation of antibacterial agents (e.g. Ag and Cu) at the surface of biomedical materials has evolved as a potentially effective method for preventing the bacterial infections. However, the antibacterial efficacy of medical device implants must necessarily be balanced by good corrosion resistance and the corrosion behavior of the antibacterial coatings has seldom been reported. In this work, Zn-incorporated antibacterial TiO₂ coating was produced on pure titanium (Ti) by micro-arc oxidization (MAO) and the electrochemical behavior was assessed. The results obtained from the antibacterial studies suggest that the Zn-incorporated TiO₂ coating provides bactericidal activity against both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) over 90%. The corrosion behavior of Zn-incorporated TiO₂ coating were investigated using a combination of complementary electrochemical measurement techniques such as open circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy. The results show that the Zn-incorporated TiO₂ coating move the OCP to the positive direction and increase the polarization resistance, thereby enhances the corrosion resistance of pure Ti. Collectively, the Zn-incorporated TiO₂ coating with both antibacterial ability and anti-corrosive properties might be more suitable for biomedical surfaces.     

Quaternary and pentanary mesoporous bioactive glass nanoparticles as novel nanocarriers for gallic acid: Characterisation,drug release and antibacterial activity

Mesoporous bioactive glass nanoparticles (MBGNs) have gained considerable attention as multifunctional platforms for simultaneously releasing ions and phytotherapeutic compounds. Thus, in the first part of this study, MBGNs based on the 53SiO₂–4P₂O₅–20CaO–23Na₂O (wt %) (S53P4) composition were synthesized by a microemulsion assisted sol-gel method. More precisely, P₂O₅ was substituted with B₂O₃ and Na₂O with MgO and/or ZnO. For B containing MBGNs all ions were successfully incorporated into the borosilicate structure without inducing crystallisation. In contrast, for S53P4 a poorly crystalline hydroxyapatite phase was identified. All MBGNs had a typical spherical shape with an internal radial network of mesopores. Additionally, for S53P4 a second fraction of particles with a smaller size and compact core was observed. Secondly, the feasibility of MBGNs as nanocarriers for gallic acid (GA) was evaluated. All drug-loaded samples showed a similar in vitro release profile which can be divided into three main phases: burst release, slow release and sustained release. Among the different compositions, S53P4 exhibited the highest cumulative release, whereas B and Mg containing particles exhibited the opposite. The presence of Zn in the MBGN compositions improved their antibacterial effect against both E. coli and S. aureus. Moreover, it was shown that depending on the MBGNs’ composition, the antibacterial activity of GA loaded MBGNs can be enhanced. Thus, the results proved that MBGNs can be used as controlled drug delivery system and, by tailoring the composition, a synergistic antibacterial effect can be achieved, considering that GA and biologically active ions are simultaneously released.     

Structural characterisation of a VMgO catalyst used in the oxidative dehydrogenation of propane

A VMgO catalyst (containing 14 wt% vanadium) that is used in the oxidative dehydrogenation of propane (ODHP) reaction has been examined in detail by in situ EXAFS, in situ XRD and HREM. These characterisation techniques have revealed that, as prepared, the catalyst is in effect a three-component system comprising discrete magnesium orthovanadate (Mg₃V₂O₈) particles, magnesium oxide and a disordered vanadium-containing overlayer supported on the MgO. When the catalyst is exposed to typical ODHP reaction conditions at $500^\circ {\text{C}}$ the in situ EXAFS indicates a change in vanadium oxidation state from 5+ to 3+. Under the same conditions, in situ XRD suggests that Mg3V2O8 transforms to a cubic spinel type structure with a lattice parameter of 8.42 Å. These changes are reversible on exposure to air at $500^\circ {\text{C}}$ . HREM shows that the overlayer on MgO changes from a disordered state to a weakly ordered structure after exposure to normal reaction conditions whilst pure propane (strongly reducing conditions) induces pronounced structural ordering of the overlayer. Image simulations have led us to the conclusion that the ordered layer comprises a cubic spinel (MgV₂O₄) phase in parallel epitaxy with the MgO support. The surface regions of the bulk Mg₃V₂O₈ particles are also found to undergo structural modification under typical reaction conditions decomposing to a mixture of MgO crystallites and MgV₂O₄; strong reduction causes a complete conversion to MgV₂O₄.     

Effect of MgO on structural,thermal and conducting properties of V2-xMgxO5-δ (x = 0.05–0.30) systems

MgO containing vanadate glasses of composition V_2-xMg_xO_5-δ (x?=?0.05, 0.10, 0.15, 0.20, 0.25 and 0.30) have been prepared successfully by melt-quench technique. The structural properties of the as-quenched samples are explored with the help of X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. Thermal properties and conductivity of the samples are investigated using differential thermal analysis (DTA) and impedance spectroscopy, respectively. Density, inter-ionic distance, and fragility index are found to decrease with the addition of MgO content. Higher content of MgO improves the glass formation tendency and reduces the thermal stability of the samples. The conductivity of the V_2-xMg_xO_5-δ samples decreases as the MgO concentration increases due to hindrance in the polaronic conduction of vanadium ions. The conductivity of the samples decreases to ? 10^?4 S?m^?1 for x?=?0.30 at 300?°C, while activation energy increases to 0.38?eV. These samples may find application in solid state batteries and fuel cells due to their higher conductivity.     

Modification of mesoporous structure of silver-doped bioactive glass with antibacterial properties for bone tissue applications

Silver-containing mesoporous bioglasses powders with SiO₂–CaO–P₂O₅–Ag₂O composition have been successfully synthesized by sol-gel and evaporation-induced self-assembly (EISA) methods in presence of various amounts of surfactant (Pluronic-F127). The morphology and crystal structure of the powders were characterized by scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD). Also, the textural properties of samples have been evaluated by adsorption-desorption, Langmuir and BET methods. Accordingly, powders had a smooth surface morphology with cubic mesoporous structure and a desired surface area and pore volume. The in vitro bioactivity was assessed by SEM, XRD and Fourier transform infrared spectroscopy (FTIR) analyses. All samples enhance the formation of HA after soaking the material in simulated body fluid (SBF) solution. The antibacterial property of samples was evaluated to investigate the effect of silver content in chemical composition. The results showed an adequate antibacterial activity of the samples against Escherichia coli, Salmonella and Listeria monocytogenes.     

Antibacterial efficiency of alkali-free bio-glasses incorporating ZnO and/or SrO as therapeutic agents

A series of seven alkali-free silica-based bioactive glasses (SBG) with ZnO and/or SrO additives (in concentrations of 0–12?mol%) were synthesized by melt-quenching, aiming to delineate a candidate formulation possessing (i) a coefficient of thermal expansion (CTE) similar to the one of titanium (Ti) and its medical grade super-alloys (crucial for the future development of mechanically adherent implant-type SBG coatings) and (ii) antibacterial efficiency, while (iii) conserving a good cytocompatibility. The SBGs powders were multi-parametrically evaluated by X-ray diffraction, Fourier transform infrared and micro-Raman spectroscopy, dilatometry, inductively coupled plasma mass spectrometry, antibacterial (against Staphylococcus aureus and Escherichia coli strains) suspension inhibition and agar diffusion tests, and human mesenchymal stem cells cytocompatibility assays. The results showed that the coupled incorporation of zinc and strontium ions into the parent glass composition has a combinatorial and additive benefit. In particular, the “Z6S4” formulation (mol%: SiO₂—38.49, CaO—32.07, P₂O₅—5.61, MgO—13.24, CaF₂—0.59, ZnO—6.0, SrO—4.0) conferred strong antimicrobial activity against both types of strains, minimal cytotoxicity combined with good stem cells viability and proliferation, and a CTE (~?8.7?×?10^?6 ×?°C^?1) matching well those of the Ti-based implant materials.     

Development of antibacterial and morphological features of scaffolds based on polycaprolactone encapsulated with copper oxide/vanadium oxide for wound dressing applications

The development of highly effective dressing materials for human injuries that meet the complex requirements for clinical examination is still a challenge. In this regard, different biomaterials could be examined for wound dressing targets. Among these materials, polycaprolactone (PCL) is high biocompatible polymeric substance and has been used for numerous pharmaceutical applications. Furthermore, targeting antibacterial behavior could be done by merging additional nanoparticles such as copper oxide (CuO) and vanadium Oxide (V₂O₅). The scaffolds could be fabricated using the cast method, which is one of the most simple and facile methods. The morphological features and the surface roughness of the fabricated could be examined using X-ray diffraction, Raman spectroscopy, Fourier transform infrared (FTIR), and scanning electron microscopy (SEM) tests. The contact angle plays a significant role in studying the wettability of the scaffolds and the hydrophilic or hydrophobic behavior of the composed films. Besides the antibacterial behavior to evaluate the effectiveness of these scaffolds to protect the injury until the healing. The cell viability against human normal cells to examine the biocompatibility of the proposed compositions. In this regard, the topographical images show a smooth surface with random pores that have diameters in the range of 0.5–1.5 μm for pure PCL while, the porosity decreased with the addition of ginger and V₂O₅. The blend of CuO/V₂O₅/ginger@ PCL represents a noticeable increase in porosity with a diameter between 0.5 and 3 μm. The contact angles were recorded respectively at 55.02°, 54.12°, 53.89°, and 53.71° which refer to the tendency of the scaffolds to the hydrophilic behavior. In addition, the anti-bacterial activity of CuO/V₂O₅/ginger@PCL was represented with the diameter of the inhibition zone equal to 17.6±1.2 mm for E. coli and 12.3±1.2 mm for S. aureus.     

Multifunctional nanoporous magnetic zinc silicate-ZnFe2O4 core-shell composite for bone tissue engineering applications

Multifunctional materials have recently gained substantial attraction in bone tissue engineering because of their capabilities to solve essential problems after implantation including inflammation and osteomyelitis and also bone cancerous tissues through hyperthermia treatment. The aim of this study was to design and develop a new multifunctional composite containing a magnetic zinc ferrite as a core, and nanoporous zinc silicate as a shell via a two-step synthesis strategy to meet all above targets simultaneously. ZnFe₂O₄ particles are synthesized via solvothermal method and then coated through surfactant-assisted sol-gel method to obtain zinc silicate-ZnFe₂O₄ composite using cetyltrimethylammoniumbromide (CTAB) as a surfactant. The XRD results show that the composite has a glass-ceramic structure. The FESEM micrographs indicate the increase in the size of ZnFe₂O₄ particles because of zinc silicate formation around them. The vibrating sample magnetometer (VSM) results reveal that the formation of zinc silicate over ZnFe₂O₄ particles caused the magnetization saturation (Ms) to be reduced from 43 to 30?emu?g^?1. The antibacterial activity of the composite is evaluated against S. aureus and E. coli bacteria. Heat generation capability of the composite is assessed in vitro and results show that the composite reached the saturation temperature of 45?°C up to 510?s with 200?Oe magnetic field and constant 200?kHz frequency. Potential application of the composite as a controlled release system is assessed in vitro up to 240?h. The cell compatibility of the composite with different concentrations is assessed using osteoblast-like cells (MG63) up to 48?h.     

Investigation of the conditions required for the formation of V(C,N) during carburization of vanadium or carbothermal reduction of V2O5 under nitrogen

Phase stability diagrams of V–C–N and V–O–C–N systems were constructed as a function of carbon activity, nitrogen partial pressure, oxygen partial pressure, and solution formation characteristics to determine the conditions for the formation of V(C,N) via the carburization of vanadium or carbothermal reduction of V₂O₅ under nitrogen. The diagram showed that only V, V₂C, and V(C,N) phases would be stable in the V–C–N system. From the diagram, it was also observed that only V(C,N) exists after the carburization of vanadium under nitrogen atmosphere more than 10^?5 atm. The diagram of V–O–C–N system suggests that V₂O₅ can be reduced to V(C,N) without forming VO, owing to the high stability of the V(C,N) phase. Using these stability diagrams, the conditions for preparing V(C,N) from vanadium or V₂O₅ were deduced and the validity of the diagrams was verified using the experimental results.     

Study of surface and lattice oxygen atoms over magnesium vanadate phases by isotopic exchange with C18O2

Different magnesium vanadate phases, V-Mg-O phases (α- Mg₂V₂O₇, Mg₃V₂O₈ and β- MgV₂O₆), MgO and V₂O₅ oxides have been compared with respect to their surface properties and their oxygen exchange capacities with C¹⁸O₂ in the gas phase. By temperature- programmed desorption of carbon dioxide, the absence of any basic impurities (i.e., MgO or residual oxidised K impurities resulting from the preparation) has been evidenced on the surface of magnesium vanadate phases. This demonstrates that the catalytic properties of the magnesium vanadate phases for oxidative dehydrogenation of propane as previously studied cannot be explained by synergetic effects due to the presence of any basic component impurities since they are absent in this case. While on MgO an important surface exchange process occurs with C¹⁸O₂ of the gas phase, this exchange is very low on V₂O₅ and pure V-Mg-O phases. A comparison of the different magnesium vanadate phases in the same experimental conditions indicates that the α-Mg₂V₂O₇ phase (which exhibited the highest selectivity for oxidative dehydrogenation of propane to propene) shows the lowest lattice oxygen exchange with C¹⁸O₂ of the gas phase. This is another specificity of this phase. This revised version was published online in July 2006 with corrections to the Cover Date.     

Silver-filled polyethersulfone membranes for antibacterial applications — Effect of PVP and TAP addition on silver dispersion

Silver-filled asymmetric polyethersulfone (PES) membranes were prepared by a simple phase inversion technique. The effects of polyvinylpyrrolidone (PVP) and 2, 4, 6-triaminopyrimidine (TAP) on the surface properties of the silver-filled asymmetric membrane were investigated for antibacterial application. The dispersion of silver nanoparticles (Ag) and silver content on membrane surface were characterized using field emission scanning electron microscope (FESEM) and energy dispersive spectrometer (EDS), respectively. Results showed that smaller silver particles were formed in PES membranes when PVP and TAP were added during dope preparation. Using inductively coupled plasma mass spectrometry (ICP-MS), it is found that silver leaching has been significantly reduced up to 57% and 63% upon the addition of PVP and TAP respectively. The improved silver dispersion on membrane surfaces was able to enhance the antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) as evidenced by larger inhibition ring in agar diffusion method. The filtration of E. coli suspension (optical density = 0.31 at λ = 600 nm) carried out on prepared membranes proved that PES-AgNO₃ with TAP as dispersant appeared to inhibit almost 100% bacterial growth in rich medium. Hence, overall results showed the potential of PES-AgNO₃ with TAP to be used for antibacterial applications especially in water treatment.     

Fabrication of forsterite scaffolds with photothermal-induced antibacterial activity by 3D printing and polymer-derived ceramics strategy

Bacterial infection of the implanting materials is one of the greatest challenges in bone tissue engineering. In this study, porous forsterite scaffolds with antibacterial activity have been fabricated by combining 3D printing and polymer-derived ceramics (PDCs) strategy, which effectively avoided the generation of MgSiO₃ and MgO impurities. Forsterite scaffolds sintered in an argon atmosphere can generate free carbon in the scaffolds, which exhibited excellent photothermal effect and could inhibit the growth of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in vitro. In addition, forsterite scaffolds have uniform macroporous structure, high compressive strength (>30 MPa) and low degradation rate. Hence, forsterite scaffolds fabricated by combining 3D printing and PDCs strategy would be a promising candidate for bone tissue engineering.