Superoxide generator using polyaniline catalyst

A superoxide generator using a polyaniline catalyst was prepared. This apparatus was able to generate superoxide as 2.5 ppm of hydrogen peroxide concentration at an applied reduction current of −0.2 mA and at −0.25 V versus the saturated calomel electrode. Sterilizing of S. aureus and P. aeruginosa was confirmed by a cultivation test after 30 min of superoxide generation.     

Surface free energy and bacterial retention to saliva-coated dental implant materials--an in vitro study

The aim of the present investigation was to compare the in vitro bacterial retention on saliva-coated implant materials (pure titanium grade 2 (cp-Ti) and a titanium alloy (Ti–6Al–4V) surfaces), presenting similar surface roughness, and to assess the influence of physico-chemical surface properties of bacterial strain and implant materials on in vitro bacterial adherence. Two bacterial strains (one hydrophilic strain and one hydrophobic strain) were used and the following were evaluated: bacterial cell adherence, SFE values as well as the Lifshitz-van-der Waals, the Lewis acid base components of SFE, the interfacial free energy and the non-dispersive interactions according to two complementary contact angle measurement methods: the sessile drop method and the captive bubble method.

Our results showed similar patterns of adherent bacterial cells on saliva-coated cp-Ti and saliva-coated Ti–6Al–4V. These findings could suggest that bacterial colonization (i.e. plaque formation) is similar on saliva-coated cp-Ti and Ti–6Al–4V surfaces and indicate that both materials could be suitable for use as transgingival abutment or healing implant components. The same physico-chemical properties exhibited by saliva-coated cp-Ti and TA6V, as shown by the sessile drop method and the captive bubble method, could explain this similar bacterial colonisation. Therefore, higher values of total surface free energy of saliva-coated cp-Ti and saliva-coated TA6V samples (γ_SV ≈65 mJ/m²) were reported using the captive bubble method indicating a less hydrophobic character of these surfaces than with the sessile drop method (γ_S ≈44.50 mJ/m²) and consequently possible differences in oral bacterial retention according the theory described by Absolom et al.

The number of adherent hydrophobic S. sanguinis cells was two-fold higher than that of hydrophilic S. constellatus cells. Our results confirm that physico-chemical surface properties of oral bacterial strains play a role in bacterial retention to implant materials in the presence of adsorbed salivary proteins.     

Effect of Lactobacillus challenge on Gardnerella vaginalis biofilms

Bacterial vaginosis (BV) is the most common infectious condition in women. It is caused primarily by anaerobic bacteria which rapidly form biofilms recalcitrant to antibiotic treatment, elevate vaginal pH, induce inflammatory processes and displace indigenous lactobacilli from the vault. Gardnerella vaginalis is commonly associated with these infections. Microscopy analysis showed that within 72 h, viable G. vaginalis covered a surface area of 567 μm², reached a depth of 16 μm and a density of approximately 104 μm³. They maintained these levels for a further 3 days unless challenged with lactobacilli strains. Lactobacillus reuteri RC-14 produced the biggest displacement of Gardnerella. This was not due to pH, which remained between 4.7 and 5.1 for all experiments, nor by hydrogen peroxide which is produced in low amounts by strain L. reuteri RC-14, high amounts by L. crispatus 33820 and not at all by L. rhamnosus GR-1. Deconvolution microscopy showed changes in structure and viability of the biofilms, with loss of dense Gardnerella biofilm pods. For the first time, a strain of L. iners, the most commonly isolated vaginal Lactobacillus in healthy women, was tested for potential probiotic properties. It was found to disrupt Gardnerella biofilm surface area, density and depth, albeit to a lesser extent than L. reuteri RC-14. These studies help to provide insight into the clinical situation in which probiotic and indigenous vaginal lactobacilli can interfere with Gardnerella's presence and reduce the risk of bacterial vaginosis.     

Calorimetric comparison of the interactions between salivary proteins and Streptococcus mutans with and without antigen I/II

Antigen I/II can be found on streptococcal cell surfaces and is involved in their interaction with salivary proteins. In this paper, we determine the adsorption enthalpies of salivary proteins to Streptococcus mutans LT11 and S. mutans IB03987 with and without antigen I/II, respectively, using isothermal titration calorimetry. In addition, protein adsorption to the cell surfaces was determined spectrophotometrically. S. mutans LT11 with antigen I/II, yielded a much higher, exothermic adsorption enthalpy at pH 6.8 (ranging from −2073 × 10⁻⁹ to −31707 × 10⁻⁹ μJ per bacterium) when mixed with saliva than did S. mutans IB03987 (−165 × 10⁻⁹ to −1107 × 10⁻⁹ μJ per bacterium) at all bacterial concentrations studied (5 × 10⁹, 5 × 10⁸, and 5 × 10⁷ ml⁻¹), largest effects per bacterium being observed for the lowest concentration. However, the enthalpy of salivary protein adsorption to S. mutans LT11 became smaller at pH 5.8. Adsorption isotherms for the S. mutans LT11 showed considerable protein adsorption at pH 6.8 (1.2–2.1 mg/m²), that decreased only slightly at pH 5.8 (1.1–1.6 mg/m²), with the largest amount adsorbed at the lowest bacterial concentration. This suggests that the protein(s) in the saliva with the strongest affinity for antigen I/II is (are) readily depleted from saliva. In conclusion, antigen I/II surface proteins on S. mutans play a determinant role in adsorption of salivary proteins through the creation of enthalpically favorable adsorption sites.     

Mucin coating on polymeric material surfaces to suppress bacterial adhesion

Mucin, a group of large glycoproteins, constitutes one of the major components of mucous which covers the lumenal surfaces of epithelial organs and serves as a physical barrier between the extracellular milieu and the plasma membrane. The molecules have a generic structure consisting of a thread-like peptide backbone with densely packed carbohydrate side chains. Protein and carbohydrate contents are about 30 and 50%, respectively. On hydrophobic materials in aqueous environments the naked parts of mucin’s protein backbone will adhere due to their hydrophobicity, while the carbohydrate side chains are thought to orient themselves away from the surface. This gives the mucin molecules their unique properties as surfactants, i.e. they tend to adsorb to hydrophobic surfaces via protein-surface interactions while they hold water molecules via their hydrophilic oligosaccharide clusters. In the present work, bovine submaxillary gland mucin (BSM) is purified by SEC and subsequently characterized with PAGE. Four polymeric materials, PMMA, silicone, Tecoflex® polyurethane and polystyrene, are selected as coating targets. Contact angle measurements show significant changes in these materials after coating with BSM. Surface concentrations of adsorbed BSM are determined by amino acid analysis and found to correlate well with observed reductions in contact angle. Both Staphylococcus aureus and CNS S. epidermidis are used to contaminate uncoated and BSM coated surfaces of all four materials, demonstrating a correlation between suppression of bacterial adhesion and surface concentration of BSM. Thus, bacterial counts on the coated PMMA, PS, PU and silicone specimens amount to ≈3, 10, 8 and 30% of the counts found on their uncoated counterparts. These results suggest that mucin coatings could profitably be employed to reduce the risk of microbial infections on polymeric biomaterials.     

pH可逆激活型不对称菁光敏剂的光动力杀菌活性

研究了一种pH可逆激活型不对称菁(Acy)的光动力杀菌性能。 结果表明,Acy在细菌所处弱酸性微环境和808 nm激光照射下可特异性激活产生单线态氧,对大肠杆菌和金黄色葡萄球菌均展现出了很好的光动力杀菌效果,而在正常体液条件下无明显的抗菌作用。 这种可特异性激活的光动力特性使得Acy避免了传统光敏剂因缺乏细菌特应性而产生的非特异性损伤,在细菌感染的特异性治疗方面展现出了良好的应用前景。     

A Highly Efficient Aggregation-induced Emission Photosensitizer for Photodynamic Combat of Multidrug-resistant Bacteria

With the antibiotic abuse and the resulting increased antibiotic resistance,the bacterial infection has posed a serious threat to human health.Photodynamic therapy is an effective tool for treating localized and superficial infections.It is a promising approach for the treatment of superbugs and with minimal risk of induced antibiotic resistance.Herein,an isoquinolinium-based photosensitizer,LIQ-TPE,with aggregation-induced emission properties is designed and synthesized.It is with high 1O2 generation efficiency and shows efficient antibacterial performance towards both Gram-negative and Gram-positive bacteria,and even methicillin-resistant Staphylococcus aureus(MRSA).LIQ-TPE thus shows great promise as an effective antimicrobial agent to combat the menace of multi-drug resistant bacteria.     

“Cell adhesion resistant,UV curable,polymer zinc oxide nanocomposite materials for intraocular lens application”

Foldable acrylic lenses are used for surgical replacement of diseased intraocular lens in treatment of cataract. One of the main postsurgical complications of this treatment method is postcapsular opacification caused by proliferating epithelial cells. The most common approach taken by research community to address this issue has been modification of lens surface with hydrophobic or hydrophilic moieties to manipulate surface cell interaction. In the present study, inherently cell repellent photopolymer resins are presented. Taking advantage of zinc oxide antiproliferative properties, its nanocomposite resins were made and investigated. Hydrophobically modified zinc oxide nanoparticles and poly(phenylethylacrylate‐co‐phenylethyl methacrylate) were made, and their nanocomposite films were prepared by UV polymerization. Films made with 5 wt% ZnO nanoparticles in them resisted fibroblast attachment substantially. In addition, these films filtered harmful UV light and showed other necessary properties like visible light transparency, glass transition temperatures, mechanical strength, and biocompatibility necessary for making intraocular lenses.     

聚(ε-己内酯)-多肽共聚物胶束增强抗生素的抗菌活性

Bacterial infection is a major threat to human health, and can cause several diseases including gastroenteritis, influenza, tetanus, and tuberculosis. As conventional antibiotic treatment may cause various undesirable effects such as stomach disorder and bacterial resistance, it is necessary to improve the antibacterial efficiency of antibiotics. Here, we synthesized a peptide-based copolymer, poly(ε-caprolactone)-block-poly(glutamic acid)-block-poly(lysine-stat-phenylalanine)[PCL₃₄-b-PGA₃₀-b-P(Lys₁₆-stat-Phe₁₂)] by ring-opening polymerization (ROP) of ε-caprolactone and amino acid N-carboxyanhydride (NCA). Successful synthesis of the copolymer was verified by proton nuclear magnetic resonance and size exclusion chromatography. This copolymer can self-assemble into negatively charged micelles (-26.7 mV) under alkaline conditions by solvent switch method. The micelle structure was confirmed by transmission electron microscopy and dynamic light scattering, and revealed to have a diameter of ~42 nm. Antibiotics were loaded into micelles during the self-assembly process, and cell viability assay was conducted to evaluate its cytotoxicity with and without tobramycin. No obvious cytotoxicity was observed for both micelles when the concentration was lower than 300 μg·mL^-1. The antibiotic-loaded micelles demonstrated very low minimum inhibitory concentrations (MICs) against both Gram-negative Escherichia coli (E. coli) (7.8 μg·mL^-1) and Gram-positive Staphylococcus aureus (S. aureus) (18.2 μg·mL^-1), while the MICs of free tobramycin were 3.9 and 1.0 μg·mL^-1, respectively. The drug-loading content and efficiency of the micelles were 5.2% and 24.3%, respectively. Therefore, the MICs of the loaded tobramycin against E. coli and S. aureus were 0.4 and 0.9 μg·mL^-1, respectively, suggesting that the micelle could enhance the antibacterial activity of antibiotics. Tobramycin-loaded micelles demonstrated a sustained release characteristic, with 85% of the antibiotics released after 8 h. In bacteria-induced acidic microenvironment, the coil conformation of PGA blocks transforms and PGA blocks shrink toward the micelle core. Concomitantly, the carboxyl side chains are protonated in an acidic environment, increasing the hydrophobicity of this micelle. Antibiotics will be captured when reaching the outer core to slow down the releasing process. Furthermore, the poly(lysine-stat-phenylalanine) [P(Lys-stat-Phe)] coronas with broad spectrum intrinsic antibacterial activity can penetrate the bacterial cell membrane, leading to leakage of the cellular contents of the bacteria and ultimately their death. Due to the sustained release property of micelle and the intrinsic activity of the antibacterial peptide segments, this micelle can greatly enhance the antibacterial activity of antibiotics. Overall, this antibiotic-loaded micelle provides a novel approach for significantly reducing the antibiotics dosage and avoiding the associated health risks.     

Spring constants and adhesive properties of native bacterial biofilm cells measured by atomic force microscopy

Bacterial biofilms were imaged by atomic force microscopy (AFM), and their elasticity and adhesion to the AFM tip were determined from a series of tip extension and retraction cycles. Though the five bacterial strains studied included both Gram-negative and -positive bacteria and both environmental and laboratory strains, all formed simple biofilms on glass surfaces. Cellular spring constants, determined from the extension portion of the force cycle, varied between 0.16+/-0.01 and 0.41+/-0.01 N/m, where larger spring constants were measured for Gram-positive cells than for Gram-negative cells. The nonlinear regime in the extension curve depended upon the biomolecules on the cell surface: the extension curves for the smooth Gram-negative bacterial strains with the longest lipopolysaccharides on their surface had a larger nonlinear region than the rough bacterial strain with shorter lipopolysaccharides on the surface. Adhesive forces between the retracting silicon nitride tip and the cells varied between cell types in terms of the force components, the distance components, and the number of adhesion events. The Gram-negative cells' adhesion to the tip showed the longest distance components, sometimes more than 1 microm, whereas the shortest distance adhesion events were measured between the two Gram-positive cell types and the tip. Fixation of free-swimming planktonic cells by NHS and EDC perturbed both the elasticity and the adhesive properties of the cells. Here we consider the biochemical meaning of the measured physical properties of simple biofilms and implications to the colonization of surfaces in the first stages of biofilm formation.     

儿茶素-稀土配合物的合成、表征及抗菌活性

以稀土(Re³⁺)和儿茶素(C)为原料,由液相合成法制备了3种(La³⁺-C、Gd³⁺-C、Er³⁺-C)配合物,结合傅里叶变换红外光谱、紫外光谱、X射线光电子能谱及配位数测定对配合物结构进行表征,确定了配合物的配位数为8。并采用牛津杯法、最小抑菌浓度(MIC)及最小杀菌浓度(MBC)等三种方法测定了Re³⁺-C对大肠杆菌、金黄色葡萄球菌、绿脓杆菌、沙门氏菌4种食源性细菌的抗菌性能。结果表明,这3种稀土配合物对各试验菌株均表现不同程度的抑制能力,相较Re³⁺和C而言,Re³⁺-C配合物的抑菌性能均有显著的提高。Re³⁺-C的抑菌活性顺序为：Gd³⁺-C > La³⁺-C > Er³⁺-C,其中Gd³⁺-C对4种细菌的MIC值分别为：1.550、0.097、0.780、1.550 μmol·mL⁻¹,MBC值分别为3.100、0.194、1.550、1.550 μmol·mL⁻¹,Gd³⁺-C对金黄色葡萄球菌表现出最佳的抑菌和杀菌能力。     

紫杉二烯生物合成模块与不同底盘的适配

以酿酒酵母BY4742及其单敲菌株作为底盘细胞, 优化底盘细胞甲羟戊酸途径, 上调并融合表达牻牛儿基牻牛儿基焦磷酸(GGPP)合成的相关基因, 引入人工合成的外源GGPP合成酶基因与紫杉二烯合成酶基因, 构建了多载体紫杉二烯生物合成模块; 还利用酵母组装技术, 通过对紫杉二烯合成路径相关基因进行模块化设计组装, 构建了依托单一着丝粒(CEN)质粒的紫杉二烯生物合成模块. 将构建的2个模块与不同底盘细胞进行适配, 使紫杉二烯产量获得了数倍提升, 最高产量可达74.84 mg/L.     

Electrospun PVA Nanofibrous Membranes Reinforced with Silver Nanoparticles Impregnated Cellulosic Fibers: Morphology and Antibacterial Property

To enhance the mechanical and antibacterial properties of silver nanoparticle impregnated cellulosic fibers, carboxy-cellulose nanocrystals(CCNs) were grafted with chitooligosaccharide(COS), which was used as a stabilizer for silver nanoparticles (AgNPs). Nanofibrous membranes reinforced with silver nanoparticle impregnated cellulosic fibers(CCN-COS-AgNP) were prepared via electrospinning using polyvinyl alcohol(PVA) as a matrix. The effects of CCN-COS-AgNP contents on the morphology, surface composition, mechanical properties, and antibacterial performances of the prepared CCN-COS-AgNP/PVA membranes were examined. The addition of CCN-COS-AgNP certainly improved the mechanical properties and antibacterial performances of the PVA nanofibers. The tensile strength was significantly increased from 4.40 MPa to 8.60 MPa when 8% CCN-COS-AgNP(mass ratio) was introduced. When 10%(mass ratio) CCN-COS-AgNP was added, the nanofibers showed an excellent antibacterial activity for S. aureus(Staphylococcus aureus) and E. coli(Escherichia coli), with the maximum inhibition zones of 2.30 and 1.60 cm, respectively. Moreover, the 2%(mass ratio) CCN-COS-AgNP/PVA fibrous membrane showed 126% cell viability for mg63 human osteoblasts. The electrospun PVA membrane has great potential application in biomedical field.     

One Step Fabrication and Application of Antibacterial Electrospun Zein/Cinnamon Oil Membrane Wound Dressing via In situ Electrospinning Process

Antibacterial wound dressing can benefit the wound healing by preventing bacterial infection, especially for the electrospun ones due to their porous structures and easily loading antibacterial drugs. However, it is challenging to apply the antibacterial electrospun wound dressing to covering the wound conveniently and safely. Here, we presented one step fabrication and application of antibacterial electrospun zein/cinnamon oil wound dressing via a handheld electrospinning setup. The prepared zein/cinnamon oil wound dressing showed gas permeability of (76.1±5.45) mm/s, hydrophilicity with zero body fluid contact angle, swelling stability after 24 h as well as antibacterial zones over 5 cm against both E. coli and S. aureus bacteria. Moreover, in situ electrospinning process can deposit the electrospun zein/cinnamon oil fibers directly onto the wound, meantime forming a wound dressing. The mice cut-wound model experiment demonstrated that the one step in situ fabrication and application of zein/cinnamon oil wound dressing could nearly heal the wound within 11 d.     

Reactive intermediates in asymmetric cross-coupling catalysed by palladium P-N chelates

The palladium dibromide complexes of (S,R)-(1,1′-bis-diphenylphosphino)-2-ferrocencylthyldimethylamine and (S,R)-(1-diphenylphosphino)-2-ferrocenylethyldimethylamine have been reduced with dilithiocyclooctatetraene to form the corresponding Pd⁰ cyclooctatetraene complexes. Their reactions with E-4-methoxy-2′-bromophenylethene, and then benzylmagnesium chloride at −60 to −30°C, provide information on the structure of intermediates in asymmetric cross-coupling.     

Evaluation of epifluorescence image analysis of biofilm growth on stainless steel surfaces

Biofilm growth of Bacillus subtilis, Pseudomonas fragi, Pediococcus inopinatus and Listeria monocytogenes was studied on stainless steel surfaces at room and low temperatures to evaluate the results of traditional hygiene measures. The results were compared with those of image analysis of stainless steel surfaces in an epifluorescence microscope. Statistical analyses were carried out to determine the variations between the conventional cultivation swab method, the glycocalyx amount obtained using swabbing, and the values of the areas of the biofilm, slime and cells. As a general rule, old biofilms showed total counts at approximately the same levels as the young biofilm. The results showed that temperature affected the results for all strains except B. subtilis. The strains of Pe. inopinatus and Ps. fragi showed increased attachment at 6°C and L. monocytogenes at 25°C. The biofilm slime was more easily detached than the cells. The results indicated that the traditional swab method is not reliable for the measurement of biofilm formation on surfaces.     

Formation of colloidal silver nanoparticles stabilized by Na+-poly(gamma-glutamic acid)-silver nitrate complex via chemical reduction process

Macromolecular and polyanionic Na⁺–poly(γ-glutamic acid) (PGA) silver nitrate complex acted as both a metal ion provider and a particle protector to fabricate nanosized silver colloids under chemical reduction by dextrose. The formation and size of particles have been characterized from transmission electron microscopy (TEM), dynamic light scattering analysis and UV–vis spectrophotometer. The results showed that the average particle size was 17.2 ± 3.4 to 37.3 ± 5.5 nm, apparently depending on the complex concentration. It was found that the rate constant and conversion of silver nanoparticles were proportional to the concentration of PGA. The growth mechanism of nanosized silver colloid was fully discussed. In addition, the in vitro cytotoxicity evaluated by L929 fibroblasts proliferation and antibacterial activity against Gram-positive strain (methicillin-resistant S. aureus (MRSA)) and Gram-negative strain (P. aeruginosa) bacteria have been assessed.     

Light-Triggered Nitric Oxide Release by a Photosensitizer to Combat Bacterial Biofilm Infections

Bacterial biofilms are a serious global health concern, often responsible for persistent infections. New strategies to prevent and treat bacterial infections by eradication of the biofilms are urgently needed. A novel ruthenium-based compound is reported in this study that functions as both a boronic acid-decorated photosensitizer (PS) and a light-triggered nitric oxide (NO) releasing agent. The compound can selectively attach to the bacterial membrane and biofilms and it is highly potent at eradicating Pseudomonas aeruginosa biofilms through the simultaneous release of NO and reactive oxygen species (ROS). The compound, which is more effective than clinical antibiotic tobramycin, also has excellent bacterial specificity and shows no significant cytotoxicity to human cells. The results reveal potential applications of this innovative dual-functional photoactivated ruthenium compound to combat bacterial biofilm infections.     

改性壳聚糖抗菌纳米微球的制备

以卤胺化合物为抗菌基团对壳聚糖接枝改性, 并制备成纳米微球, 提高壳聚糖的抗菌性能. 通过核磁共振和紫外光谱对改性壳聚糖进行结构表征; 探讨了改性壳聚糖浓度、 三聚磷酸钠浓度及两者体积比对纳米微球的形成和粒径分布的影响; 测定了纳米微球的抗菌性能. 结果表明, 在改性壳聚糖浓度为4.0 mg/mL, 三聚磷酸钠浓度为2.0 mg/mL时, 形成的纳米微球形态稳定, 粒径分布均匀, 氯化后的纳米微球可在30 min内杀灭10⁷ cfu(cfu为单位体积中的菌落总数)的金黄色葡萄球菌和大肠杆菌, 表现出优异的抗菌性能.     

Physicochemical aspects of microbial adhesion — Influence of antibody adsorption on the deposition ofStreptococcus sobrinus in a parallel-plate flow chamber

Deposition of the oral bacteriumStreptococcus sobrinus HG977 onto glass (water contact angle 0°) and onto FEP-Teflon (fluoroethylenepropylene; water contact angle 110°) was studied in a parallel-plate flow chamber in the presence and absence of polyclonal antibodies (pAb) and monoclonal antibodies (mAbs) adsorbed onto the cells. The zeta potentials of the bacteria ranged from −7.1 to −8.5 mV at pH 6.8 and were not affected by the presence of pAb or mAbs. Hydrophobicity (by water contact angles) increased from 30° (no antibodies) to 88° in the presence of pAb adsorbed onto the bacterial cell surface. The untreatedS. sobrinus had a greater tendency to adhere to glass (44.5 × 10⁶ cm⁻²) than to FEP-Teflon (18.3 × 10⁶ cm⁻²), in accordance with thermodynamic modelling. After preincubation ofS. sobrinus with pAb, its clear preference for adhesion to glass disappeared as expected from its increased hydrophobicity. Although forS. sobrinus preincubated with OMVU10 no difference was found in hydrophobicity in comparison to the untreated bacteria, the number of bacteria adhering to glass decreased to 10.2 ¢ 10⁶ cm⁻². Formation of bacterial aggregates was found whenS. sobrinus, preincubated with pAb or OMVU10, adhered to glass and FEP. This was also observed when untreated bacteria adhered to glass coated with OMVU10, or to FEP coaled with OMVU10 or pAb. Adhesion in these experiments is therefore thought to occur via near-neighbour collection induced by the presence of pAb or mAbs. Low numbers of bacteria were removed from glass after draining the flow cell, whereas high numbers of untreated bacteria and bacteria preincubated with OMVU10 were removed from FEP.S. sobrinus cells preincubated with pAb were not removed but piled up. It was concluded that the adhesion of untreatedS. sobrinus andS. sobrinus preincubated with pAb is in accordance with thermodynamic modelling, based on the overall wettability of the cell surfaces, whereas the adhesion ofS. sobrinus preincubated with OMVU10 may be through localized interactions, not expressed in overall surface properties.