Adhesion of slime producing Staphylococcus epidermidis strains to PVC and diamond-like carbon/silver/fluorinated coatings

Staphylococcus epidermidis has emerged as a pathogen associated with infections of implanted medical devices. Bacterial adhesion is a crucial step in infection on biomaterial surfaces. To quantitatively determine the relationship between poly (vinyl chloride) (PVC) surface properties and bacterial adhesion, we have compared attachment of slime-producing S. epidermidis strains on PVC and various coatings under flow conditions. Bacterial adhesion and colonization was quantified by counting the viable organisms on the adherent surface as well as by scanning electron microscopy, epifluorescence microscopy and atomic force microscopy. Fluorination of the PVC surface encourages S. epidermidis adhesion whereas; diamond-like carbon (DLC) and especially silver (Ag) coatings seem to inhibit its adhesion. In most materials, the number of adherent bacteria decreased with the increase of shear rate. These results indicate that bacterial adhesion is influenced by the chemical properties of the polymeric surfaces, the surface roughness and the associated flow conditions.     

Silver coated bioactive glass particles for wound healing applications

Bioactive glass particles (0.42SiO₂–0.15CaO–0.23Na₂O–0.20ZnO) of varying size (<90 μm and 425–850 μm) were synthesized and coated with silver (Ag) to produce Ag coated particles (PAg). These were compared against the uncoated analogous particles (Pcon.). Surface area analysis determined that Ag coating of the glass particles resulted in increased the surface area from 2.90 to 9.12 m²/g (90 μm) and 1.09–7.71 m²/g (425–850 μm). Scanning electron microscopy determined that the Ag coating remained at the surface and there was little diffusion through the bulk. Antibacterial (Escherichia coli—13 mm and Staphylococcus epidermidis—12 mm) and antifungal testing (Candida albicans—7.7 mm) determined that small Ag-coated glass particles exhibited the largest inhibition zones compared to uncoated particles. pH analysis determined an overall higher pH consider in the smaller particles, where after 24 h the large uncoated and Ag coated particles were 8.27 and 8.74 respectively, while the smaller uncoated and Ag coated particles attained pH values of 9.63 and 9.35 respectively.     

Preparation and antimicrobial activity of poly (vinyl chloride)/gelatin/montmorillonite biocomposite films

The aim of this study was using a novel antimicrobial thermoplastic plasticizer based on aliphatic anhydride derivative dodecenyl succinic anhydride (DSA) for blending poly (vinyl chloride), PVC, with gelatin in presence of montmorillonite (MMT) using Brabender via polymer melting technique. This anhydride-based plasticizer blended the membrane ingredients homogenously under melting process. The used plasticizer exhibited high performance antimicrobial potency for some biomedical and industrial applications. The prepared biocomposite films were evaluated for antimicrobial activity using agar disc diffusion method against gram-positive and gram-negative bacteria such as: Staphylococcus aureus (S. aureus), Klebsiella pneumonia (K. pneumonia), Bacillus cereus (B. cereus), Bacillus subtilis (B. subtilis) and Escherichia coli (E. coli). The majority of these biocomposites, except the plasticized PVC with DOP, have shown inhibitory effect at different concentrations (1.0–20) mg/ml against all above mentioned bacteria. However, C. albicans and A. niger were the most resistant strains.     

Fabrication of silver nanocomposite films impregnated with curcumin for superior antibacterial applications

Silver nanocomposite films are found to be very effective material for anti-bacterial application. In the present work, sodium carboxylmethyl cellulose silver nanocomposite films (SCMC SNCF) were tried for antibacterial applications. To enhance their applicability novel film-silver nanoparticle-curcumin composites have been developed. SCMC SNCF are developed from sodium carboxylmethyl cellulose (SCMC), N,N ¹ -methylenebisacrylamide (MBA) and silver nitrate solution. These films were characterized by FTIR, UV–visible, XRD, TGA, DSC and TEM techniques. The formed silver nanoparticles have an average particle size of ~15 nm as observed by transmission electron microscopy (TEM). Curcumin loading into SCMC SNCF is achieved by diffusion mechanism. The UV–Visible analysis indicated that higher encapsulation of curcumin in the films with higher SCMC content. Further, it was observed that the presence of silver nanoparticles in the films enhanced the encapsulation of curcumin indicating an interaction between them. Moreover, the antibacterial activity showed that the SCMC films generated with silver nanoparticles have a synergistic effect in the antimicrobial activity against Escherichia coli (E. coli). In order improve the healing efficacy as antibacterial agents, curcumin loaded with SCMC SNCFs were developed which showed significant inhibition of E. coli growth than the silver nanoparticles and curcumin alone film. Therefore, the present study clearly provides novel antimicrobial films which are potentially useful in preventing/treating infections.     

In vitro adhesion of staphylococci to diamond-like carbon polymer hybrids under dynamic flow conditions

This study compares the ability of selected materials to inhibit adhesion of two bacterial strains commonly implicated in implant-related infections. These two strains are Staphylococcus aureus (S-15981) and Staphylococcus epidermidis (ATCC 35984). In experiments we tested six different materials, three conventional implant metals: titanium, tantalum and chromium, and three diamond-like carbon (DLC) coatings: DLC, DLC–polydimethylsiloxane hybrid (DLC–PDMS-h) and DLC–polytetrafluoroethylene hybrid (DLC–PTFE-h) coatings. DLC coating represents extremely hard material whereas DLC hybrids represent novel nanocomposite coatings. The two DLC polymer hybrid films were chosen for testing due to their hardness, corrosion resistance and extremely good non-stick (hydrophobic and oleophobic) properties. Bacterial adhesion assay tests were performed under dynamic flow conditions by using parallel plate flow chambers (PPFC). The results show that adhesion of S. aureus to DLC–PTFE-h and to tantalum was significantly (P < 0.05) lower than to DLC–PDMS-h (0.671 ± 0.001 × 10⁷/cm² and 0.751 ± 0.002 × 10⁷/cm² vs. 1.055 ± 0.002 × 10⁷/cm², respectively). No significant differences were detected between other tested materials. Hence DLC–PTFE-h coating showed as low susceptibility to S. aureus adhesion as all the tested conventional implant metals. The adherence of S. epidermidis to biomaterials was not significantly (P < 0.05) different between the materials tested. This suggests that DLC–PTFE-h films could be used as a biomaterial coating without increasing the risk of implant-related infections.     

Comparison of antibacterial properties of commercial bone cements and fillers with a zinc-based glass polyalkenoate cement

Postoperative infection following invasive surgical procedures is a significant cause for concern, particularly in spinal reconstructive surgery. The objective of this study is to compare the antibacterial efficacy of a novel zinc-based glass polyalkenoate cement (Zn-GPC) based on 0.04SrO–0.12CaO–0.36ZnO–0.48SiO₂ glass, to a number of commercially available bone cements and fillers including Simplex P + Tobramycin (S_Tob), Spineplex (S_pine) and Novabone Putty (N_Put). The agar diffusion test was performed on each material against Escherichia coli, Staphlococcus epidermidis, Pseudomonas aeruginosa and Staphlococcus Aureus. S_Tob was found to produce large inhibition zones in each of the bacteria tested and was statistically significantly higher than any other material. The experimental Zn-GPC (B_TSC) was found to exhibit antibacterial properties in both E. coli and S. epidermidis. Neither S_pine nor N_Put showed any inhibitory effect in any of the bacteria tested. A study was also performed to determine the effect of antibiotic release from S_Tob and Zn-GPC (B_Tob) containing the antibiotic tobramycin (Tob). Antibacterial efficacy was found to increase with respect to maturation with B_Tob, whereas S_Tob was found to decrease significantly over the time period of 0–14 days. The final objective is to investigate any change in agar composition during the agar-diffusion test. Little change was observed for S_Tob as antibiotic release cannot be determined using EDX. There was, however, an increase in Zn levels when analysing B_TSC which suggests that Zn is playing a role in the antimicrobial nature of the Zn-GPC. No significant changes were observed for S_pine or N_Put.     

Highly Stable and Dispersive Silver Nanoparticle–Graphene Composites by a Simple and Low‐Energy‐Consuming Approach and Their Antimicrobial Activity

A simple and low‐energy‐consuming approach to synthesize highly stable and dispersive silver nanoparticle–graphene (AgNP–GE) nanocomposites has been developed, in which the stability and dispersivity of the composites are varied greatly with the pH value and temperature of the reaction. The results demonstrate that the optimal reaction conditions are pH 11 at room temperature for 70 min. As‐synthesized composites display excellent antimicrobial activity, and can completely inhibit the growth of Escherichia coli cells at a concentration of 20 mg L^?1 (20 ppm). After treatment with 10 ppm AgNP–GE composites, the cells are killed completely within 3 h. The unique structure imparts such good antimicrobial properties to the composites. Firstly, the sheetlike AgNP–GE tends to be adsorbed and accumulated onto the surface of cells, which can change the permeability and enhance the antimicrobial activity. Secondly, Ag⁺ released from AgNPs can act on the cells effectively and fully, thereby resulting in cell death.     

Preparation and characterization of poly(vinyl chloride) calcium carbonate nanocomposites via melt intercalation

Calcium carbonate was synthesized by in situ deposition technique and its nano size (35–60 nm) was confirmed by transmission electron microscopy (TEM). Composites of the filler CaCO₃ (micro and nano) and the matrix poly(vinyl chloride) (PVC) were prepared with different filler loadings (0–5 wt%) by melt intercalation. Brabender torque rheometer equipped with an internal mixer has been used for preparation of formulations for composites. The effect of filler content both nano- and micro level on the nanostructure and properties is reported here. The nanostructures were studied by wide angle X-ray diffraction and scanning electron microscopy. The mechanical, thermal, and dynamic mechanical properties of PVC/micro- and nano-CaCO₃ composites were characterized using universal testing machine, thermogravimetric analyzer, and dynamic mechanical analyzer. The results of thermal analysis indicated that the thermal stability of PVC/nano-CaCO₃ composites was improved as compared with corresponding microcomposites, and that of pristine PVC and maximum improvement was obtained at 1 and 3 phr loadings. However, the tensile strength decreased significantly with increase loading of both nano- and micro-CaCO₃, whereas storage modulus and glass transition temperature increased significantly.     

Biocide activity of diatom-silver nanocomposite

Diatom-nAg composites containing 1 wt.% of metallic silver nanoparticles (≤ 20 nm) have been obtained by a colloidal route and chemical reduction. This nanostructured powder has proved to be a selective green inorganic biocide which reduces the starting concentrations of Escherichia coli and Micrococcus luteus cultures by at least 5 orders of magnitude, while completely inactive against yeast. Diatom-nAg can be considered as a selective inorganic biocide particularly suitable for the food and pharmacological sectors. The silver nanoparticles are released from the diatom surface to the liquid media in a controlled manner, reaching a concentration (< 11 ppm) far below the toxicity limit for human cells.     

Effect of B2O3 and CuO additions on the sintering temperature and microwave dielectric properties of 3Li2O–Nb2O5–3TiO2 ceramics

The effects of B₂O₃–CuO (BCu, the weight ratio of B₂O₃ to CuO is 1:1) addition on the sintering behavior, microstructure, and the microwave dielectric properties of 3Li₂O–Nb₂O₅–3TiO₂ (LNT) ceramics have been investigated. The low-amount addition of BCu can effectively lower the sintering temperature of LNT ceramics from 1125 to 900 °C and induce no obvious degradation of the microwave dielectric properties. Typically, the 2 wt% BCu-added ceramic sintered at 900 °C has better microwave dielectric properties of ε _r  = 50.1, Q × f = 8300 GHz, τ _f  = 35 ppm/°C. Silver powders were cofired with the dielectric under air atmosphere at 900 °C. The SEM and EDS analysis showed no reaction between the dielectric ceramic and silver powders. This result shows that the LNT dielectric materials are good candidates for LTCC applications with silver electrode.     

Molecular characterizations,mechanical properties and anti-algal activities for PVC and wood/PVC composites containing urea- and triazine-based algaecides

Material behaviors and anti-algal performances of PVC and wood PVC composites (WPVCs) were examined after adding commercial algaecides of different types and contents. Three different wood types commonly found in tropical climates – namely, Xylia kerrii Craib and Hutch.; Hevea brasiliensis Muell.; and Mangifera indica Linn. – were of interest. Isoproturon (3-(4-isopropylphenyl)-1,1-dimethylurea), a urea-based algaecide, and Terbutryn (N²-tert-butyl-N⁴-ethyl-6-methylthio-1,3,5-triazine-2,4-diamine), a triazine-based algaecide, were used as anti-algal agents in this study; concentrations in the specimens varied from 0 to 1500 ppm. Surface color, thermal properties, chemical structure and mechanical properties of the materials were also monitored. The results revealed that addition of Isoproturon tended to considerably change the surface color of the materials, particularly for PVC which had the highest ΔE^* value, whereas addition of Terbutryn did not. The effect of wood types was found to influence the initial surface color of the materials. Evidence based on DSC, FT-IR and contact angle testing indicated that Isoproturon had a strong molecular interaction with PVC and could induce PVC degradation. The mechanical properties of PVC and WPVC were affected by the addition of wood, but not by algaecide addition. The results of the growth inhibition zone and chlorophyll-a content in Chlorella vulgaris TISTR 8580 suggested that Terbutryn exhibited better anti-algal performance than Isoproturon with a recommended dosage of 1000 ppm while Isoproturon at 1500 ppm could act as an effective coupling agent in WPVC composites.     

Novel alginate based nanocomposite hydrogels with incorporated silver nanoparticles

Alginate colloid solution containing electrochemically synthesized silver nanoparticles (AgNPs) was investigated regarding the nanoparticle stabilization and possibilities for production of alginate based nanocomposite hydrogels in different forms. AgNPs were shown to continue to grow in alginate solutions for additional 3 days after the synthesis by aggregative mechanism and Ostwald ripening. Thereafter, the colloid solution remains stable for 30 days and could be used alone or in mixtures with aqueous solutions of poly(vinyl alcohol) (PVA) and poly(N-vinyl-2-pyrrolidone) (PVP) while preserving AgNPs as verified by UV–Vis spectroscopy studies. We have optimized techniques for production of Ag/alginate microbeads and Ag/alginate/PVA beads, which were shown to efficiently release AgNPs decreasing the Escherichia coli concentration in suspensions for 99.9% over 24 h. Furthermore, Ag/hydrogel discs based on alginate, PVA and PVP were produced by freezing-thawing technique allowing adjustments of hydrogel composition and mechanical properties as demonstrated in compression studies performed in a biomimetic bioreactor.     

Dielectric, ferromagnetic and ferroelectric properties of the (1 ? x)Ba0.8Sr0.2TiO3–xCoFe2O4 multiferroic particulate ceramic composites

The (1 − x)Ba_0.8Sr_0.2TiO₃–xCoFe₂O₄ ceramic composites (x = 0–1) were prepared by standard solid state reaction method. X-ray diffraction and SEM indicate the Ba_0.8Sr_0.2TiO₃ (BST) phase and CoFe₂O₄ (CFO) phase coexist in the composites. The dielectric constant and dielectric loss for the composites were studied as a function of frequency (40 Hz–1 MHz) and temperature (30–600 °C). Magnetic and ferroelectric tests show that the ceramic composites display ferromagnetic and ferroelectric properties simultaneously. The saturated polarization of the composites decrease with ferrite concentration increasing, while the remnant polarization of the composites increase with increasing ferrite concentration. The enhanced ferroelectricity of composites may be attributed to space charge contribution in the composites.     

High thermal conductivity composites consisting of diamond filler with tungsten coating and copper (silver) matrix

Tungsten coatings with thickness of 5–500 nm are applied onto plane-faced synthetic diamonds with particle sizes of about 430 and 180 μm. The composition and structure of the coatings are investigated using scanning electron microscopy, X-ray spectral analysis, X-ray diffraction, and atomic force microscopy. The composition of the coatings varies within the range W–W₂C–WC. The average roughness, R _a, of the coatings’ surfaces (20–100 nm) increases with the weight–average thickness of the coating. Composites with a thermal conductivity (TC) as high as 900 W m⁻¹ K⁻¹ are obtained by spontaneous infiltration, without the aid of pressure, using the coated diamond grains as a filler, and copper or silver as a binder. The optimal coating thickness for producing a composite with maximal TC is 100–250 nm. For this thickness the heat conductance of coatings as a filler/matrix interface is calculated as G = (2–10) × 10⁷ W m⁻² K⁻¹. The effects of coating composition, thickness and roughness, as well as of impurities, on wettability during the metal impregnation process and on the TC of the composites are considered.     

Thermal and dielectric properties of the LTCC composites based on the eutectic system BaO–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript>–B<Subscript>2</Subscript>O<Subscript>3</Subscript>

The low-temperature co-fired ceramic (LTCC) composites containing quartz based on the eutectic system BaO–Al₂O₃–SiO₂–B₂O₃ are fabricated at the sintering temperature below 980 °C. Preparation process and sintering mechanism were described and discussed, respectively. The results indicated that the addition of quartz to the eutectic system can availably improve dielectric properties of the LTCC composites. In addition, The LTCC composites with optimum compositions, which were obtained by the regulation of an Al₂O₃ content in the composite, can express excellent dielectric properties (permittivity: 5.94, 5.48; loss: 7 × 10⁻⁴, 5 × 10⁻⁴), considerable CTE values (11.7 ppm. °C⁻¹, 10.6 ppm. °C⁻¹) and good mechanical properties (128 MPa,133 MPa).     

Antibacterial properties of padded PP/PE nonwovens incorporating nano-sized silver colloids

This paper deals with the effects that nano-sized silver colloids have on the antibacterial properties of PE/PP nonwovens against three kinds of bacteria: Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli. These silver colloids comprise silver nanoparticles that are a non-toxic and non-tolerant disinfectant. PE/PP nonwovens are used as back sheets or coverstocks of baby diapers, adult diapers, sanitary napkins, and wipes. These materials are readily contaminated by bacteria present in moisture and dirt and can cause disease. We finished the nonwovens using a normal dipping–pad–dry method. From SEM images, we determined that the silver nanoparticles were generally dispersed well on the surface of the nonwoven fibers. We used the AATCC-100 test method to study the antibacterial properties of the treated fabrics. Bacteria were disinfected completely to below a count of 10 cells after 10 min when using the samples treated with 10 ppm of silver colloids. The ethanol-based silver/sulfur composite colloid (SNSE) has the best antibacterial efficacy when compared with the other nano-sized silver colloids. The silver particles having the smallest sizes gave the higher dispersibilities and the strongest antibacterial efficacies.     

Electrical and mechanical properties of antistatic PVC films containing multi-layer graphene

In order to explore practical application of graphene as novel conductive fillers in the filed of composite materials, we prepared anti-static multi-layer graphene (MLG) filled poly(vinyl chloride) (PVC) composite films by using conventional melt-mixing method, and investigated electrical conductivity, tensile behavior, and thermal properties of the MLG/PVC composite films. We found that the presence of MLG can greatly increase electrical conductivity of the MLG/PVC composites, and the surface electrical conductivity of the MLG/PVC composites is less than 3 × 10⁸ Ohm/square when the MLG loading is about 3.5 wt%, meeting anti-static requirement for commercial anti-static PVC films. On the other hand, the MLG/PVC composites exhibited higher tensile modulus and higher glass transition temperature than neat PVC, which is closely associated with crumpled morphology of the MLG and good compatibility between components of the MLG/PVC composites. By virtue of its satisfied anti-static performance and high mechanical properties, the MLG/PVC composites exhibit great potential to be used as high-performance antistatic materials in many fields.     

Magnetoelectric and electrical properties of WO3-doped (Ni0.8Zn0.1Cu0.1)Fe2O4/[Pb(Ni1/3Nb2/3)O3–Pb(Zn1/3Nb2/3)O3–PbTiO3] composites

A total of 5 mol% WO₃-doped (1−x)(Ni_0.8Zn_0.1Cu_0.1)Fe₂O₄/xPb(Ni_1/3Nb_2/3)O₃–Pb(Zn_1/3Nb_2/3)O₃–PbTiO₃ ((1−x)NZCF/xPNN-PZN-PT) magnetoelectric particulate ceramic composites were prepared by conventional solid-state reaction method via low-temperature sintering process. X-ray diffraction (XRD) measurement and scanning electron microscopy (SEM) observation indicate that piezoelectric phase and ferrite phase coexist in the sintered particulate ceramic composites. Dielectric property of the (1−x)NZCF/x0.53PNN–0.02PZN–0.05Pb(Ni_1/2W_1/2)O₃–0.40PT ((1−x)NZCF/xPNN-PZN-PNW-PT, nominal composition) composites is improved greatly as compared to that of the undoped (1−x)NZCF/xPNN-PZN-PT composites. The WO₃-doped (1−x)NZCF/xPNN-PZN-PT composites exhibit typical P–E hysteresis loops at room temperature accompanied by the decrease of saturation polarization (P _s) and remnant polarization (P _r). At the same time, piezoelectric property of the composites deteriorates greatly with the increase of ferrite content. The (1−x)NZCF/xPNN-PZN-PNW-PT composites can be electrically and magnetically poled and exhibit apparent magnetoelectric (ME) effect. A maximum ME voltage coefficient of 13.1 mV/(cm Oe) is obtained in the 0.1NZCF/0.9PNN-PZN-PNW-PT composite at 400 Oe d.c. magnetic bias field superimposed 1 kHz a.c. magnetic field with 5 Oe amplitude. The addition of WO₃ in the piezoelectric phase decreases sintering temperature greatly from 1180 °C to 950 °C and decreases dielectric loss sharply of the composites, thus the ME voltage coefficient increases. Such ceramic processing is valuable for the preparation of magnetoelectric particulate ceramic composites with excellent ME effect.     

Thermal expansion of a novel hybrid SiC foam–SiC particles–Al composites

A new type of hybrid SiC foam–SiC particles–Al composites (V_SiC = 53, 56.2 and 59.9%) to be used as an electronic packaging substrate material were fabricated by squeeze casting technique, and their thermal expansion behavior was evaluated. The coefficients of thermal expansion (CTEs) of the hybrid composites in the range of 20–100 °C were found to be between 6.6 and 7.7 ppm/°C. The measured CTEs are much lower than those of SiC particle-reinforced aluminum (SiC_p–Al) composites with the same content of SiC because of the characteristic interpenetrating structure of the hybrid composites. A material of such a low CTE is ideal for electronic packaging because of the low thermal mismatch (and therefore, low thermal stresses) between the electronic component and the substrate. To achieve similar CTEs in SiC_p–Al composites, the volume fraction of SiC would be much higher than that in the hybrid composites.     

Templated synthesis of mesoporous aluminas by <Emphasis Type="Italic">graft</Emphasis> copolymer and their CO<Subscript>2</Subscript> adsorption capacities

Mesoporous aluminas were synthesized via a sol–gel process by templating an amphiphilic graft copolymer, PVC–g–POEM, consisting of a poly(vinyl chloride) (PVC) backbone and poly(oxyethylene methacrylate) (POEM) side chains. The mesoporous structures of aluminas with large surface areas were confirmed by X-ray diffraction, transmission electron microscopy, and nitrogen adsorption/desorption analysis. Aluminas synthesized with PVC–g–POEM graft copolymer exhibited higher CO₂ adsorption capacities (0.7 mol CO₂/kg sorbent) than aluminas synthesized without graft copolymer (0.6 mol CO₂/kg sorbent). The adsorption capacity of alumina strongly depends on its structure and calcination temperature; amorphous (400 °C) > γ phase (800 °C) > α phase (1000 °C).