Enhanced antibacterial activity of Ag-doped ZnO/polyaniline nanocomposites

Ag _x Zn_1?x O_1?0.5x and Ag_0.02Z_0.98O_0.99/polyaniline (AZO/PANI) nanocomposites were prepared by citrate sol–gel method and in situ inverse microemulsion method, respectively. The composition, structure and morphology of the samples were characterized by means of modern testing techniques. The antibacterial activities of the as-prepared samples against Staphylococcus aureus, Escherichia coli and Candida albicans were carried out using inhibition zone, minimum inhibitory concentration and minimal bactericidal concentrations methods under the irradiation of sunlight. Results showed that the antibacterial activity of Ag _x Zn_1?x O_1?0.5x was better than that of ZnO, and it was optimum when the mole ratio of Ag was 0.02. The AZO/PANI composites had preferable antibacterial effect than AZO, and shown the strongest antibacterial activity when the mass fraction of AZO was up to 60 %.     

Investigation of the antibacterial activity and efflux pump inhibitory effect of co-loaded piperine and gentamicin nanoliposomes in methicillin-resistant Staphylococcus aureus

Objective: Antibiotic resistance has stimulated the research for developing novel strategies that can prevent bacterial growth. Methicillin-resistant Staphylococcus aureus (MRSA), regarded as one of the most serious antibiotic-resistant bacteria which has been conventionally recognized as a nosocomial pathogen.

Materials and methods: Nanoliposomal formulations of piperine and gentamicin were prepared by dehydration-rehydration (DRV) method and characterized for size, zeta potential and encapsulation efficiency. Antibactericidal activities of liposomal and free forms were evaluated against MRSA ATCC 43300 by the determination of minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and fractional inhibitory concentration index (FICI). The time-kill studies were carried out to evaluate the potency of antibacterial agents. The effect of piperine on bacterial efflux pumps was also investigated.

Results: MIC values of gentamicin and piperine were 32 and 100?µg/mL, respectively. Synergetic effects were observed by the combination of gentamicin and piperine and FICI was determined to be 0.5. Following incorporation of gentamicin into liposomal gentamicin and liposomal combination, the MIC values were reduced 16- and 32-fold, respectively. MBC values of gentamicin reduced 4 and 8 times following incorporation into gentamicin and combination liposomes, respectively. In comparison with vancomycin, liposomal combination was more effective in bacterial inhibition and killing. Liposomal combination was the most effective preparations in time-kill study. Our findings indicated that liposomal piperine was able to inhibit the efflux pump sufficiently.

Conclusion: The results of this study revealed that liposomal combination is a powerful nano-antibacterial agent to eradicate MRSA infection. This dual-loaded formulation was an effective approach for eradication of MRSA.     

抗菌天然橡胶纳米复合材料的研制

研究了自制ZnO/Ag纳米复合抗菌剂的亲油改性,利用改性后的ZnO/Ag纳米复合抗菌剂制备天然橡胶(NR)纳米复合材料,探讨了抗菌NR纳米复合材料的抗菌、抗藻性能.结果表明:ZnO/Ag纳米复合抗菌剂经磷酸三丁酯(TBP)改性后,沉降率从接近1减小到0.2以下,亲油性和稳定性大大提高,将TBP改性后的抗菌剂加入到油性介质正己烷中,抗菌剂分散均匀,粒径在100nm以内;在NR纳米复合材料的制备中,随着ZnO/Ag纳米复合抗菌剂添加量的增加,正硫化时间减小;经检测,抗菌NR纳米复合材料对大肠埃希氏菌的抗菌率达98%以上,且抗菌率随抗菌剂添加量的增加而增大,抗藻性能达到最优零级标准.     

硫脲壳聚糖/蒙脱土纳米中间体的合成及其对大肠杆菌抑菌性能的研究

通过插层技术合成了硫脲壳聚糖/蒙脱土(Cts-TU/MMT)纳米中间体,利用XRD和FT-IR对合成的硫脲壳聚糖/蒙脱土纳米中间体进行了表征,结果表明硫脲壳聚糖已经进入了蒙脱土层间,其层间距达到3.529nm;通过抑菌动力学实验评价了硫脲壳聚糖/蒙脱土纳米中间体对大肠杆菌的抑菌性能,预示了其在生物医药领域的潜在应用性。     

Enhanced antibacterial activity and mechanism studies of Ag/Bi2O3 nanocomposites

In this work, sphere-like Ag/Bi₂O₃ nanocomposites with the average size of ca. 170?nm were successfully synthesized by simple deposition-precipitation method. The antibacterial activities of as-prepared Ag/Bi₂O₃ nanocomposites were evaluated by minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and colony counting methods. It was found that Ag/Bi₂O₃ nanocomposites displayed greatly improved antibacterial ability against common pathogenic Gram-positive and Gram-negative bacteria in comparison with single-component Bi₂O₃ nanospheres. More importantly, Ag/Bi₂O₃ nanocomposites exhibited remarkably outstanding antibacterial activities against clinical drug-resistant bacteria. The antibacterial activity of Ag/Bi₂O₃ nanocomposite increased with the increase of Ag content and 15?wt% Ag/Bi₂O₃ nanocomposites showed the highest antibacterial activity. Furthermore, a plausible antibacterial mechanism of Ag/Bi₂O₃ nanocomposite was proposed. It was believed that the enhanced generation of H₂O₂ could lead to the membrane leakage of cytosol and the inactivation of respiratory chain dehydrogenaes, which was possibly responsible for the enhanced antibacterial activities of nanocomposites.     

Synthesis and characterization of waterborne polyurethane/Cu(II)-loaded hydroxyapatite nanocomposites with antibacterial activity

A novel kind of environmentally friendly nanocomposites, waterborne polyurethane (WBPU)/Cu(II)-loaded hydroxyapatite (CuHAp), with improved physical properties and antibacterial activity have been prepared via in-situ polymerization from functionalized CuHAp nanoparticles (CuHAp NPs). The interaction of the CuHAp NPs with isophorone diisocyanate to form the functionalized CuHAp NPs containing isocyanate groups (CuHAp-g-NCO) has been studied. The microstructure and particle distribution of the nanocomposites were observed using scanning electron microscopy. The improvements of mechanical properties, thermal stability and water resistance of the nanocomposites have also been evaluated. Finally, the antibacterial activity was tested against G(-) Escherichia coli and G(+) Staphylococcus aureus by the zone of inhibition test and the direct contact test. The long-lasting antibacterial activity was studied by measuring antibacterial ability of the nanocomposites after being immersed in water. The results indicate that WBPU incorporation with CuHAp NPs shows strong antibacterial activity upon contact, and long-lasting antibacterial property.     

仿生矿化的镁合金降解和抑制金黄色葡萄球菌性能研究

通过对壳聚糖(CS)进行改性,成功制备了壳聚糖季铵盐(HACC)。经过FT-IR、1 H NMR表征,证实了其分子结构。采用在仿生溶液中添加CS或HACC的方法,在微弧氧化前后的镁合金样品表面修饰得到4种不同的仿生涂层。利用SEM和XRD对涂层分析表明,仿生矿化后的镁合金表面为含有CaP/CS或CaP/HACC的复合涂层。降解实验表明,微弧氧化后仿生矿化的样品失重率小于微弧氧化前仿生矿化的样品;利用ICP测定释放的镁、铝离子浓度,发现镁离子浓度先升高后降低,铝离子浓度越来越小。抑菌实验结果表明,含有CaP/HACC比含有CaP/CS的复合涂层样品对金黄色葡萄球菌具有更明显的抑菌作用;对于仿生溶液中添加同样浓度的CS或HACC,微弧氧化后比微弧氧化前矿化的样品抑菌率高。比浊法测定显示,4种涂层在4d内均具有不同程度的抑菌效果,微弧氧化后的镁合金样品在添加有HACC的仿生溶液中矿化得到的涂层抑菌率最高。研究说明,改性后的HACC比CS具有更强的抑菌作用;微弧氧化后的样品具有更强的抗腐蚀能力和载药性能。     

Bispecific antibody-mediated detection of the Staphylococcus aureus thermonuclease

We report a novel fluorescence-based immunoassay which enables qualitative detection of the Staphylococcus aureus Thermonuclease (TNase) enzyme, thus providing confirmation of the presence of the S. aureus bacterium in vitro. The biomedical problem of chronic wound healing and the continuing emergence of antibiotic-resistant species is addressed in the development of a detection system capable of the rapid, real-time assessment of bacterial load and diversity. The use of bispecific antibodies (BsAb) provides integration of the molecular detection and signal response components of a standard immunoassay due to steric hindrance-mediated release of prebound fluorescent reporter molecules upon specific binding of TNase to adjacent sites. Rhodamine and fluorescein-labeled hemocyanin from Megathura crenulata (KLH) were prepared as effective immunoconjugates containing a sensitive fluorescent reporter moiety. BsAb that both specifically quenched the fluorescence of the reporter conjugate and bound the TNase target antigen were produced using cell fusion techniques. Assays were then performed to analyze the properties attributable to the steric hindrance-mediated release of the fluorescent reporter molecules upon adjacent TNase binding. This was performed by monitoring the intensity of fluorescence emission of the immunogenic reporter conjugate released into an aqueous environment at 578 and 520 nm, respectively.     

Evaluation of antibacterial property of hydroxyapatite and zirconium oxide‐modificated magnetic nanoparticles against Staphylococcus aureus and Escherichia coli

In the first section of this research, superparamagnetic nanoparticles (NPs) (Fe₃ O₄) modified with hydroxyapatite (HAP) and zirconium oxide (ZrO₂) and thereby Fe₃ O₄ /HAP and Fe₃ O₄ /ZrO₂ NPs were synthesised through co‐precipitation method. Then Fe₃ O₄ /HAP and Fe₃ O₄ /ZrO₂ NPs characterised with various techniques such as X‐ray photoelectron spectroscopy, X‐ray diffraction, scanning electron microscopy, energy dispersive X‐ray analysis, Brunauer–Emmett–Teller, Fourier transform infrared, and vibrating sample magnetometer. Observed results confirmed the successful synthesis of desired NPs. In the second section, the antibacterial activity of synthesised magnetic NPs (MNPs) was investigated. This investigation performed with multiple microbial cultivations on the two bacteria; Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Obtained results proved that although both MNPs have good antibacterial properties, however, Fe₃ O₄ /HAP NP has greater antibacterial performance than the other. Based on minimum inhibitory concentration and minimum bactericidal concentration evaluations, S. aureus bacteria are more sensitive to both NPs. These nanocomposites combine the advantages of MNP and antibacterial effects, with distinctive merits including easy preparation, high inactivation capacity, and easy isolation from sample solutions by the application of an external magnetic field.Inspec keywords: nanocomposites, X‐ray chemical analysis, microorganisms, magnetic particles, scanning electron microscopy, precipitation (physical chemistry), nanomagnetics, X‐ray diffraction, X‐ray photoelectron spectra, nanoparticles, superparamagnetism, iron compounds, antibacterial activity, biomedical materials, nanomedicine, calcium compounds, nanofabrication, Fourier transform infrared spectra, magnetometers, zirconium compoundsOther keywords: antibacterial effects, antibacterial property, superparamagnetic nanoparticles, X‐ray photoelectron spectroscopy, X‐ray diffraction, X‐ray analysis, antibacterial activity, bactericidal concentration, S. aureus bacteria, Staphylococcus aureus, Escherichia coli, hydroxyapatite, coprecipitation method, scanning electron microscopy, energy dispersive X‐ray analysis, Brunauer‐Emmett‐Teller method, Fourier transform infrared spectroscopy, vibrating sample magnetometer, microbial cultivations, nanocomposites     

Synthesis of ZnO/Fe3 O4 /rGO nanocomposites and evaluation of antibacterial activities towards E. coli and S. aureus

Antibacterial activity of nanoparticles (NPs) and nanocomposites (NCs) has received wide spread attention in biomedical applications. In this direction, the authors prepared zinc oxide (ZnO), iron oxide (Fe₃ O₄), and their composite including reduced graphene oxide (rGO) by hydrothermal method. The structural and microstructural properties of the synthesised NPs and NCs were investigated by XRD, FT‐IR, UV‐Vis, TGA, and TEM analysis. PEG‐coated ZnO and Fe₃ O₄ form in hexagonal wurtzite and inverse spinel structures, respectively. ZnO forms in rod‐shaped (aspect ratio of ∼3) morphology, whereas well‐dispersed spherical‐shaped morphology of ∼10 nm is observed in Fe₃ O₄ NPs. The ZnO/Fe₃ O₄ composite possesses a homogeneous distribution of above two phases and shows a very good colloidal stability in aqueous solvent. These synthesised particles exhibited varying antibacterial activity against gram‐positive strain Staphylococcus aureus (S. aureus) and gram‐negative strain Escherichia coli (E. coli). The nanocomposite exhibits a better cidal effect on E. coli when compared to S. aureus when treated with 1 mg/ml concentration. Further, the addition of rGO has intensified the anti‐bacterial effect to a much higher extent due to synergistic influence of individual components.Inspec keywords: colloids, visible spectra, II‐VI semiconductors, thermal analysis, nanofabrication, X‐ray diffraction, nanoparticles, biomedical materials, wide band gap semiconductors, transmission electron microscopy, ultraviolet spectra, antibacterial activity, nanocomposites, zinc compounds, nanobiotechnology, Fourier transform infrared spectra, graphene compounds, iron compounds, crystal growth from solution, crystal morphologyOther keywords: antibacterial activity, E. coli, biomedical applications, iron oxide, hydrothermal method, structural properties, microstructural properties, PEG‐coated ZnO, hexagonal wurtzite, inverse spinel structures, gram‐positive strain Staphylococcus aureus, S. aureus, gram‐negative strain Escherichia coli, nanocomposites, nanoparticles, XRD, FTIR spectra, UV‐vis spectra, TGA, TEM, rod‐shaped morphology, spherical‐shaped morphology, colloidal stability, cidal effect, ZnO‐Fe₃ O₄ ‐CO     

Synergistic effects of micro-/nano-fillers on conductive and electromagnetic shielding properties of polypropylene nanocomposites

This study presents the synergistic effects of graphene nanosheets (GNSs) and carbon fibers (CFs) additions on the electrical and electromagnetic shielding properties of GNS/CF/polypropylene (PP) composites. These composites were fabricated by the melt blending of different ratios of GNSs and CFs (20:0, 15:5, 10:10, 5:15 and 0:20 wt/wt%) into a PP polymer matrix using a Brabender mixer. Besides, the chemical and crystalline structures and the thermal stability of the resultant GNS/CF/PP composites were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and thermogravimetric analysis (TGA). FT-IR and XRD showed that with the addition of GNSs content, transmittances at 1373.4?cm^?1 and 1454.4?cm^?1 became smaller and the characteristic peak at 26.82° became stronger. TGA showed that the GNS/CF/PP composite can be used at high temperature below 456°C. Blending 10?wt% CFs and 10?wt% GNSs into the PP polymer resulted in excellent conductivity (0.397 S/cm), which indicated the occurrence of the critical percolation threshold phenomenon, and also reached the maximum electromagnetic shielding effectiveness (EMSE) of 20?dB at 1.28–2.00?GHz. Laminated with five layers of composites, its EMSE achieved 25–38?dB at 0.3–3.0?GHz, corresponding to blocking of 94.38–98.74% electromagnetic waves.     

Staphylococcus aureus adhesion to different treated titanium surfaces

Staphylococcus aureus is a major pathogen, associated with medical-device related infections. Converting biomaterial surfaces into non-interactive surfaces requires a specific surface/interface design. One approach is to polish the surface, and a second is to coat the surface with an antimicrobial or protein resistant coating. This study showed that polishing a titanium surface or coating titanium with various treatments that decreased the surface's coefficient of friction, had no significant effect on minimising S. aureus adhesion to these surfaces under static conditions in comparison to standard medical grade titanium. The cell promoting coating, TAST, was found to increase the S. aureus density on its surface as expected. The only coating that significantly decreased the density of adhering S. aureus was the titanium surface coated with sodium hyaluronate. Thus such a coating could have potential use as a coating for ostoesynthesis, orthopaedic or dental implants.     

金华火腿中金黄色葡萄球菌的聚合酶链式反应检测

建立了一种用于金华火腿中金黄色葡萄球菌的聚合酶链式反应(PCR)检测方法.针对金黄色葡萄球菌独有的肠毒素基因(sea)设计了一对特异引物,在PCR体系中对相应片断进行扩增,扩增产物通过电泳技术与阳性对照进行对比来判断阴阳性.结果表明,该方法检出率高,样品中模板DNA含量仅有0.05 pg即可检出金黄色葡萄球菌,24 h即可报告结果.因此,PCR方法可以作为一种高效、敏感、特异性高的检测技术,用于金华火腿中金黄色葡萄球菌的快速检测.     

Caco-2 cells permeability evaluation of nifuroxazide derivatives with potential activity against methicillin-resistant Staphylococcus aureus (MRSA)

Throughout the period of evaluation and selection in drug development, the assessment of the permeability potential of a compound to achieve an efficient refinement of the molecular structure has been widely appraised by the transport of substances across cell monolayers. This study aims to develop in vitro assays through Caco-2 cells in order to analyze the permeability of 5-nitro-heterocyclic compounds analogues to nifuroxazide with antimicrobial activity, especially showing promising activity against multidrug-resistant Staphylococcus aureus (MRSA). Caco-2 cell monolayers cultivated for 21 days in Transwell® plates were used for the in vitro permeability assays. The quantification of the nifuroxazide derivatives in the basolateral chambers was performed by a validated high performance liquid chromatography with UV (HPLC-UV) method. Apparent permeability values (Papp) show that these compounds can be considered as new drug candidates with the potential to present high absorption in vivo, according to the classifications of Yee and Biganzoli. The thiophenic derivatives showed permeability values higher than the furanic ones, being AminoTIO the compound with the greatest potential for the development of a new drug against MRSA, since it showed the best cytotoxicity, permeability and solubility ratio among all the derivatives.     

食品中金黄色葡萄球菌肠毒素及检测方法的研究进展

金黄色葡萄球菌肠毒素食物中毒是国内外主要细菌性食物中毒之一。本文简要阐述了金黄色葡萄球菌肠毒素的理化特性、生物活性和致病作用等方面的研究成果,并对其多种检测方法的若干新进展特别是在食品中的应用进行了重点介绍。     

Complications associated with the development of bacteremia with Staphylococcus aureus

Access-related infections are a leading cause of morbidity and mortality among hemodialysis patients. Staphylococcus aureus bacteremia accounts for 25% of these episodes. Nissenson et al., found that 20.7% of the patients developing S. aureus bacteremia had infectious complications as well as hospital readmissions related to the S. aureus bacteremia. This retrospective analysis did not determine whether the S. aureus bacteremia was access related, nor how each episode was treated. We have prospectively collected a database of all access-related S. aureus bacteremia developing in our unit between 1/1/03 and 8/31/05, including the management of the access. Episodes of S. aureus bacteremia with an identifiable source other than the vascular access were excluded. Seventy-two episodes of S. aureus bacteremia were identified; 54 developed in patients using a catheter and 18 developed in patients using an arteriovenous graft/fistula. The mean age was 64+/-15 years, and 56% of the patients were Caucasian. All patients were treated with 4 weeks of antibiotics. A total of 6 (8%) deaths and 15 (20.8%) infectious complications related to the S. aureus bacteremia were identified. Infectious complications included endocarditis (4), metastatic infection (7), discitis (3), and a myocardial abscess (1). Seventeen (23.6%) of the patients were readmitted within 30 days of the episode of S. aureus bacteremia; 4 readmissions were related to the S. aureus bacteremia. Five of the 54 catheter patients who developed S. aureus bacteremia expired and 14 developed infectious complications despite the catheter being removed/exchanged in all but one patient. One of the arteriovenous graft patients who developed S. aureus bacteremia expired. We conclude that infectious complications from S. aureus bacteremia are common, as 23.6% of the patients in our study developed an infectious complication. Eight percent of the patients who developed S. aureus bacteremia expired. Strategies to avoid S. aureus bacteremia are needed.     

Synthesis of polypyrrole nanocomposites decorated with silver nanoparticles with electrocatalysis and antibacterial property

Polypyrrole nanowire/silver nanoparticle composites (PPy/Ag) are obtained in aqueous media through a one-pot method without any external stimulus. PPy nanowires were assembled on the reactive self-degraded template of the complex of AgNO₃ and methyl orange (MO). During the synthesis process in the dark surrounding, Ag nanoparticles could be uniformly decorated onto the surface of PPy nanowires in situ by the redox reaction of pyrrole and AgNO₃. Neither additional reducing agents for the growth of silver nanoparticles nor oxidizing agents for the polymerization of pyrrole are utilized. The formation mechanism, morphologies, structural characteristics, and conductivity of the obtained PPy/Ag nanocomposites are reported. The as-prepared PPy/Ag nanocomposites exhibit well-defined response to the electrochemical reduction of hydrogen peroxide. Moreover, the preliminary antibacterial assays indicate that the PPy/Ag nanocomposites also possess antibacterial abilities against Escherichia coli.     

食品中金黄色葡萄球菌定量检测方法比较研究

目的：研究食品中金黄色葡萄球菌定量检测方法。方法：比较Baird—Parker平板、显色培养基A、显色培养基B、Petrifilm TM测试片等4种计数方法的生长率、选择性、检出限及人工污染食品的检验效果。结果：金黄色葡萄球菌在显色培养基A上的生长率最高,PetrifilmTM测试片的选择性最强,4种计数方法的检出限相当,检出结果与实际含菌量无显著差异。结论：选择显色培养基作为日常检验的辅助手段可大大提高检测灵敏度、缩短检验周期、节约检验成本,值得在日常检验中推广应用。