Camphor and Eucalyptol—Anticandidal Spectrum,Antivirulence Effect,Efflux Pumps Interference and Cytotoxicity

Candidaalbicans represents one of the most common fungal pathogens. Due to its increasing incidence and the poor efficacy of available antifungals, finding novel antifungal molecules is of great importance. Camphor and eucalyptol are bioactive terpenoid plant constituents and their antifungal properties have been explored previously. In this study, we examined their ability to inhibit the growth of different Candida species in suspension and biofilm, to block hyphal transition along with their impact on genes encoding for efflux pumps (CDR1 and CDR2), ergosterol biosynthesis (ERG11), and cytotoxicity to primary liver cells. Camphor showed excellent antifungal activity with a minimal inhibitory concentration of 0.125–0.35 mg/mL while eucalyptol was active in the range of 2–23 mg/mL. The results showed camphor’s potential to reduce fungal virulence traits, that is, biofilm establishment and hyphae formation. On the other hand, camphor and eucalyptol treatments upregulated CDR1; CDR2 was positively regulated after eucalyptol application while camphor downregulated it. Neither had an impact on ERG11 expression. The beneficial antifungal activities of camphor were achieved with an amount that was non-toxic to porcine liver cells, making it a promising antifungal compound for future development. The antifungal concentration of eucalyptol caused cytotoxic effects and increased expression of efflux pump genes, which suggests that it is an unsuitable antifungal candidate.     

In Vitro Cytotoxicity,Colonisation by Fibroblasts and Antimicrobial Properties of Surgical Meshes Coated with Bacterial Cellulose

Hernia repairs are the most common abdominal wall elective procedures performed by general surgeons. Hernia-related postoperative infective complications occur with 10% frequency. To counteract the risk of infection emergence, the development of effective, biocompatible and antimicrobial mesh adjuvants is required. Therefore, the aim of our in vitro investigation was to evaluate the suitability of bacterial cellulose (BC) polymer coupled with gentamicin (GM) antibiotic as an absorbent layer of surgical mesh. Our research included the assessment of GM-BC-modified meshes’ cytotoxicity against fibroblasts ATCC CCL-1 and a 60-day duration cell colonisation measurement. The obtained results showed no cytotoxic effect of modified meshes. The quantified fibroblast cells levels resembled a bimodal distribution depending on the time of culturing and the type of mesh applied. The measured GM minimal inhibitory concentration was 0.47 µg/mL. Results obtained in the modified disc-diffusion method showed that GM-BC-modified meshes inhibited bacterial growth more effectively than non-coated meshes. The results of our study indicate that BC-modified hernia meshes, fortified with appropriate antimicrobial, may be applied as effective implants in hernia surgery, preventing risk of infection occurrence and providing a high level of biocompatibility with regard to fibroblast cells.     

Surface phenomena and hydrodynamic effects on the deposition of pseudomonas fluorescens

Biofilm adhesion to metals (copper, aluminium and brass) was studied at two different velocities and pH values of 7 and 9. Both bacteria and metals showed negative surface charges at those values of pH, which tends to slow down adhesion. Film densities increased with the fluid velocity and were also affected by the pH and by the growth rate of the bacteria. Long duration tests based on heat transfer measurements were run at five different fluid velocities and at pH = 7, showing in general an asymptotic behaviour and a control of deposition by adhesion and growth phenomena.     

细菌纤维素结构与性质的初步研究

对A. xylinum X-2的发酵产物进行纤维素酶水解液的纸层析实验,发现样品的Rf值与标准葡萄糖液的Rf值相近,水解液主成分为葡萄糖。通过对细菌纤维素的的X-射线衍射图谱和固体CP/MAS 13C-NMR谱分析,表明细菌纤维素结晶度高,Iα/Iβ比例大。对细菌纤维素干膜进行渗透性实验,发现干膜透气性小,透湿性大,结构致密,含有大量极性基团。     

The effects of surface type on the removal of Bacillus cereus and Pseudomonas fluorescens single and dual species biofilms

The aim of this work was to assess the effectiveness of the biocide benzyldimethyldodecyl ammonium chloride (BDMDAC) on the removal of single and dual species biofilms of Bacillus cereus and Pseudomonas fluorescens formed in a rotating cylinder reactor (RCR), using AISI316 stainless steel (SS) and polymethyl methacrylate (PMMA) as adhesion surfaces. Additional tests were performed to understand the adhesion of B. cereus and P. fluorescens to the selected surfaces.Predictions of the adhesion potential according to the thermodynamic theory showed more favourable adhesion on SS than on PMMA, for both species. Thermodynamically, adhesion was more favourable for B. cereus. After BDMDAC treatment, thermodynamic adhesion ability was favoured for P. flurescens and decreased for B. cereus, mainly on PMMA. Both bacteria had negative surface charge and the exposure to BDMDAC increased the charge to less negative values. In vitro adhesion results were, for most cases, contradictory to those predicted by the thermodynamic theory. Single and dual species biofilms were formed in the RCR for 7 days. Afterwards, the biofilms were exposed to the chemical (use of BDMDAC) and to hydrodynamic stresses (use of increasing Reynolds number of agitation), alone and combined. The applications of BDMDAC or hydrodynamic stress, when applied alone, were insufficient to remove the biofilms from the surfaces. The combined effects of BDMDAC with a series of increasing Reynolds number of agitation promoted additional biofilm removal. This effect was dependent on the surface used. For PMMA, the hydrodynamic stress was more effective on the removal of BDMDAC-treated dual species biofilms. For SS, the synergy of the chemical and hydrodynamic stresses removed more B. cereus and dual species biofilms. The overall results demonstrate that the species association was not advantageous in biofilm resistance to removal when compared with the single species biofilms, particularly those of P. fluorescens. In general, removal by hydrodynamic stress, alone and preceded by the BDMDAC treatment, was higher for biofilms formed on SS. However, even the combined action of BDMDAC and the exposure to a series of increasing Reynolds number of agitation were not effective to obtain biofilm-free surfaces.     

金属表面处理工艺对橡胶与金属黏合性能的影响

主要介绍橡胶硫化时与金属黏合性能的相关基础理论知识,然后再根据这些理论知识来分析各种金属表面处理工艺对橡胶与金属黏合性能的影响。     

Effect of Different Crowding Agents on the Architectural Properties of the Bacterial Nucleoid-Associated Protein HU

HU is a nucleoid-associated protein expressed in most eubacteria at a high amount of copies (tens of thousands). The protein is believed to bind across the genome to organize and compact the DNA. Most of the studies on HU have been carried out in a simple in vitro system, and to what extent these observations can be extrapolated to a living cell is unclear. In this study, we investigate the DNA binding properties of HU under conditions approximating physiological ones. We report that these properties are influenced by both macromolecular crowding and salt conditions. We use three different crowding agents (blotting grade blocker (BGB), bovine serum albumin (BSA), and polyethylene glycol 8000 (PEG8000)) as well as two different MgCl₂ conditions to mimic the intracellular environment. Using tethered particle motion (TPM), we show that the transition between two binding regimes, compaction and extension of the HU protein, is strongly affected by crowding agents. Our observations suggest that magnesium ions enhance the compaction of HU–DNA and suppress filamentation, while BGB and BSA increase the local concentration of the HU protein by more than 4-fold. Moreover, BGB and BSA seem to suppress filament formation. On the other hand, PEG8000 is not a good crowding agent for concentrations above 9% (w/v), because it might interact with DNA, the protein, and/or surfaces. Together, these results reveal a complex interplay between the HU protein and the various crowding agents that should be taken into consideration when using crowding agents to mimic an in vivo system.     

细菌纤维素/氧化亚铜膜的抗菌性能及机制研究

采用抗菌试验来表征不同配方的细菌纤维素/氧化亚铜膜的特性,用大肠埃希菌和黑根霉对细菌纤维素/氧化亚铜膜进行定性分析;用大肠埃希菌和金黄色葡萄球菌对细菌纤维素/氧化亚铜膜进行定量分析,得出抑菌率。通过电镜试验,初步观察样品对细菌细胞的破坏机制,试验结果表明:不同配方的细菌纤维素/氧化亚铜膜的抗菌能力不同,抗菌机制主要是改变细胞膜通透性和抑制细胞复制,最终导致细胞死亡。     

Effect of Basalt Surface on the Properties of Boundary Layers of Network Polymers

Abstract

The activation of basalt as filler results in change of structure and properties of composite based on these fillers.     

Electrospun PEO/rGO Scaffolds: The Influence of the Concentration of rGO on Overall Properties and Cytotoxicity

Reduced graphene oxide (rGO) is one of the graphene derivatives that can be employed to engineer bioactive and/or electroactive scaffolds. However, the influence of its low and especially high concentrations on scaffolds’ overall properties and cytotoxicity has yet to be explored. In this study, polyethylene oxide (PEO)-based scaffolds containing from 0.1 to 20 wt% rGO were obtained by electrospinning. Morphological, thermal and electrical properties of the scaffolds were characterized by SEM, Raman spectroscopy, XRD, DSC and electrical measurements. The diameter of the fibers decreased from 0.52 to 0.19 µm as the concentration of rGO increased from 0.1 wt% to 20 wt%. The presence of rGO above the percolation threshold (5.7 wt%) resulted in a significantly reduced electrical resistivity of the scaffolds. XRD and Raman analysis revealed delamination of the graphene layers (interlayer spacing increased from 0.36 nm to 0.40–0.41 nm), and exfoliation of rGO was detected for the samples with an rGO concentration lower than 1 wt%. In addition, an evident trend of increasing cell viability as a function of the rGO concentration was evidenced. The obtained results can serve as further guidance for the judicious selection of the rGO content incorporated into the PEO matrix for constructing electroactive scaffolds.     

Bacterial Community Structure on Membrane Surface and Characteristics of Strains Isolated from Membrane Surface in Submerged Membrane Bioreactor

Abstract

In order to investigate the bacterial community structure and the characteristics of bacteria on the membrane surface, a submerged membrane bioreactor treating municipal wastewater was continuously operated under two different conditions. Bacterial community structures were examined by PCR‐denaturing gradient gel electrophoresis and PCR cloning of 16S rRNA genes. Bacterial strains isolated from membrane surface were identified and their growth curve, EPS concentration and hydrophobicity were measured. The structures of bacterial communities in the suspended solids and on the membrane surface were obviously different, and γ‐Proteobacteria more selectively adhere and grow on the membrane surface than other microorganisms. Most of the membrane isolates grew slowly as compared with the strains isolated from the suspended solids. Also, the membrane isolates were higher cell surface hydrophobicities, higher EPS concentrations, and higher ratios of protein to carbohydrate within the EPSs than the isolates from suspended solids.     

Bacterial decolorization of an azo dye with a natural isolate of Pseudomonas luteola and genetically modified Escherichia coli

The azo dye, Reactive Black B (RBB), was decolorized by a wild‐type isolate (Pseudomonas luteola), an Escherichia coli mutant (E coli NO3), and a recombinant strain (E coli CY1) harboring decolorizing genes from Rhodococcus sp. Decolorization of RBB by P luteola was inefficient with only 65% conversion, while color removal exceeded 90% for the two E coli strains, which were further investigated to determine the decolorization kinetics and operational stability. Kinetic studies applying a Monod‐type model showed that E coli NO3 was a more effective decolorizer for RBB than the CY1 strain. In addition, decolorization of RBB with the NO3 strain could tolerate higher temperatures and was more kinetically favorable over CY1. The optimal pH for decolorization was around 6.0–8.0 for NO3 and 8.0–10.0 for CY1. Decolorization of RBB was inhibited when the dissolved oxygen level exceeded 0.35 mg dm^?3 for both strains. E coli NO3 was more stable during repeated operations, whereas the decolorization activity of E coli CY1 slightly decreased when the strain was used repeatedly. Copyright © 2004 Society of Chemical Industry     

RAPTA-Decorated Polyacrylamide Nanoparticles: Exploring their Synthesis,Physical Properties and Effect on Cell Viability

In this study, we report the first successful immobilisation of a known cytoactive [Ru(η⁶-arene)(C₂O₄)PTA] (RAPTA) complex to a biologically inert polyacrylamide nanoparticle support. The nanoparticles have been characterised by zetasizer analysis, UV/Vis, ATR-FTIR, TGA and ICP-MS to qualitatively and quantitatively confirm the presence of the metallodrug on the surface of the carrier. The native RAPTA complex required a concentration of 50 μM to produce a cell viability of 47.1±2.1 % when incubated with human Caucasian colorectal adenocarcinoma cells for 72 h. Under similar conditions a cell viability of 45.1±1.9 % was obtained with 0.5 μM of RAPTA complex in its immobilised form. Therefore, conjugation of the RAPTA metallodrug to our nanoparticle carriers resulted in a significant 100-fold decrease in effective concentration of ruthenium required for a near identical biological effect on cell viability.     

剪切力对木葡糖醋杆菌及细菌纤维素合成的影响

以摇瓶和发酵罐两种培养体系为对象,考察了剪切力对木葡糖醋杆菌生长和细菌纤维素合成的影响。结果表明,剪切力的存在对细菌纤维素的合成不利,在添加玻璃珠的三角瓶中经9轮震荡培养后,细菌纤维素的产量降至原始菌株的23．6％;在机械搅拌罐中培养时,用剪切力大的六叶平桨进行发酵,细菌纤维素的产量最低,而用转速降低的框式桨进行发酵,细菌纤维素的产量较高。剪切力也影响木葡糖醋杆菌的形态和生长周期,剪切力的存在使细菌菌体变小,单位体积发酵液菌浓降低,菌落形态改变,菌株进入对数生长期的时间延后。实验结果为今后改进提高细菌纤维素动态培养产量提供了理论依据。     

细菌纤维素负载金纳米粒子复合膜的制备及催化性能

以细菌纤维素(BC)为基底,氯金酸(HAu Cl4)为金前驱体,通过原位还原法制备了BC负载金纳米粒子(Au NPs)复合膜。采用紫外-可见光谱仪、透射电子显微镜、X射线衍射仪、电感耦合等离子发射光谱仪和傅里叶变换红外光谱仪对复合膜的结构和性质进行了表征,并通过对硝基苯酚(4-NP)催化还原反应来评价Au NPs-BC复合催化剂的催化性能。研究结果表明:复合膜上Au NPs的粒径大小为(5.30±1.23)nm,其反应速率常数高达5.09×10-3s-1,Au NPs-BC催化剂表现出优异的催化活性及重复稳定性。     

Effect of Substrate on the Properties of Polymer Alloys and Blends

The thermodynamic aspects of the influence of the solid surface on the properties and adhesion of polymer blends and alloys are discussed. It is shown that under the influence of the surface the properties and composition of the interphase may be changed. The effects are explained by the influence of the surface on the phase equilibrium in compatible and incompatible blends.     

The Effect of Silane Surface Treatment of Carbon Fiber on the Tribological Properties of Bismaleimide(BMI) Composite

Silane surface modification method was used for the surface treatment of carbon fiber to improve the interfacial adhesion of the carbon fiber reinforced bismaleimide(BMI) composite. The surface characteristics of untreated and treated carbon fiber were characterized by Fourier transform infrared (FT-IR) spectroscope. The friction and wear properties of the BMI composites filled with differently surface treated carbon fibers(20 vol%), were investigated on a ring-on-block tribometer. Experimental results revealed that silane treatment largely reduced the friction and wear of CF/BMI composites. Scanning electron microscope (SEM) of worn surfaces of BMI composites showed that surface treated CF/BMI composite had the strongest interfacial adhesion.     

Interpenetrating Polymer Networks Based on Gelatin and Poly(Vinyl Pyrollidone): Evaluation of Degradation,Histocompatibility, Cytotoxicity,and Drug Release

Interpenetrating polymer networks (IPNs) based on crosslinked gelatin [Gx] and poly(vinyl pyrrolidone) [PVPx] were synthesized using gamma irradiation. Degradability of IPNs was found to be dependent on the irradiation dose and crosslinker concentration as well as on the composition of IPNs. Samples prepared at dose of 0.07 and 0.14 Mrad degraded within 15 days in comparison to samples prepared at higher doses [0.20, 0.25 Mrad, and 0.30 Mrad]. Cell viability and histocompatibility studies suggest that IPNs based on gelatin and PVPx can be used as biodegradable drug delivery devices.     

Model Studies of the Effect of Surface Roughness and Mechanical Interlocking on Adhesion

The apparent strength of adhesion has been measured for a soft elastic layer adhering to model porous substrates, consisting of rigid plates containing regular arrays of cylindrical holes. Two contributions to the apparent strength have been identified and compared with the predictions of a simple theoretical treatment. The first is adhesion to the surface itself. Because “rough” surfaces have greater area for bonding, the strength of adhesion was increased by as much as twenty-fold. The second arises from the work of breaking deeply embedded or entangled strands in order to detach the overlayer. Contributions from this mechanism were as much as several hundred times the (low) intrinsic strength of adhesion. Satisfactory agreement was obtained with theory in both cases. Measurements were also made using cloth substrates, when the adhering layer penetrated the cloth completely. The work of detaching and breaking permeating strands was again much larger than the intrinsic strength of adhesion, in reasonable agreement with theoretical predictions.     

F-在方解石表面的吸附及其对方解石表面性质的影响

氟元素主要存在于磷矿和萤石等矿物中,这些矿物中都伴生有方解石脉石矿物,在浮选分离的弱酸条件下,矿物表面的F^-会部分溶出并吸附到矿物表面,从而影响矿物表面性质。本文研究了F^-在方解石表面的吸附及其对方解石表面性质的影响机理。结果表明,在矿浆pH 值为5.5时,F^-以化学吸附的方式吸附在方解石表面,随着吸附时间的增加吸附量逐渐增加,90 min时方解石对F^-的吸附达到平衡。在油酸钠(NaOL)为捕收剂时,F^-的存在会降低方解石表面的疏水性。通过Zeta电位测试、溶液化学计算和X射线光电子能谱仪(XPS)分析表明,F^-会和方解石表面的Ca²⁺反应生成CaF₂沉淀,占据方解石表面的Ca位点,降低NaOL在方解石表面的吸附量。