Synthesis,spectral characterization,and in vitro antimicrobial activity in liquid medium and applied on cotton fabric of a new PAMAM metallodendrimer

A new polyamidoamine metallodendrimer modified with eight 1,8-naphthalimide units was synthesized. The Cu(II) complex has been investigated by EPR spectroscopy and it has shown that 17 copper ions have involved in the dendrimer complex. To confirm the presence of metallodendrimers on the cotton surface, scanning electron microscopy characterization has been used. In vitro antimicrobial activity of the metallodendrimer against different pathogens was investigated and compared to the dendrimer ligand free of copper ions. Both dendrimers were deposited on a cotton fabric and antibacterial activity of the treated cotton samples was investigated against model Gram-positive and Gram-negative bacteria. It has been shown that the studied dendrimers reduce bacterial growth and prevent the formation of biofilms. The metallodendrimer showed stronger antimicrobial and biofilm inhibiting abilities than those of the free of Cu(II) ions ligand.     

Antimicrobial Surgical Sutures: Recent Developments and Strategies

Surgical sutures are probably the most widely used medical devices in healthcare applications for wound closure. During their application, sutures may be exposed to microorganisms present in the environment leading to bacterial biofilm formation, and thereon to surgical site infections. The physicochemical characteristics of the polymeric substrate play a major role in directing the behavior of the suture in a biological milieu. In such a context, it is necessary to develop sutures which actively repel and inhibit bacterial adherence and colonization on their surfaces. Drug eluting sutures have been proposed as a solution to this dilemma. Currently, bioactive agents (natural or synthetic) are being incorporated in polymeric materials via various methods including blending and compounding, surface functionalization and conjugation, and coating to render antimicrobial surgical sutures. However, each of these methods has its own pros and cons. Depending upon the nature of the substrate, an appropriate processing technique has to be chosen. In this article, we review the recent state-of-the-art developments and strategies in antimicrobial surgical suture fabrication. The efficacy and mechanism of these sutures in controlling infection is critically analyzed. However, such bioactive agent incorporated sutures have to be tested in clinically randomized trials to accurately gauze their applicability in a surgical setting. Presently, very few antimicrobial surgical sutures are available commercially. Therefore, there is a great scope for market development in this area.     

Influence of temperature on performance of an anaerobic sequencing biofilm batch reactor with circulation applied to treatment of low-strength wastewater

The effect of temperature on the performance of an anaerobic sequencing biofilm batch reactor (ASBBR) with liquid-phase recirculation was assessed. Assays were performed using a recirculation velocity of 0.20 cm/s, 8-h cycles, and an average treated synthetic wastewater volume of 2 L/cycle with a concentration of 500 mg of Chemical Oxygen Demand (COD)/L. Operation temperatures were 15, 20, 25, 30, and 35°C. At 25, 30, and 35°C, organic matter removal efficiencies for filtered samples ranged from 81 to 83%. At lower temperatures, namely 15 and 20°C, removal efficiency decreased significantly to 61 and 65%, respectively. A first-order model could be fitted to the experimental concentration profile values. The first-order kinetic parameter value of this model varied from 0.46 to 0.81 h¹ considering the lowest and highest temperature studied. Moreover, analysis of the removal profile values allowed fitting of an Arrhenius-type equation with an activation energy of 5715 cal/mol.     

Antiinfective properties of ursolic acid-loaded chitosan nanoparticles against Staphylococcus aureus

The present study aimed to synthesize ursolic acid-loaded chitosan nanoparticles (UA-Ch-NPs) as an antiinfective agent against 21 Staphylococcus aureus isolates. The UA-Ch-NPs were synthesized by a simple method and then characterized by TEM, FTIR, DLS-zeta potential, and XRD analyses. According to the characterization results, highly dispersed spherical nanoparticles with a mean diameter of 258 nm and a zeta potential of + 40.1 mV were developed. The antibacterial properties of UA-Ch-NPs were investigated and their inhibitory effect on biofilm formation was demonstrated by AFM. Finally, the expression levels of icaA and icaD were measured using real-time PCR. Results indicated that the minimum inhibitory concentration (MIC) of UA and UA-Ch-NPs against S. aureus was 64 and 32 µg/mL, respectively. The treatment of bacterial cells with UA-Ch-NPs significantly decreased the expression of icaA and icaD genes which are engaged in biofilm formation. Our results indicated that UA-Ch-NPs could be a promising material for antibacterial and antibiofilm applications.     

青岛港湾微型污损生物群落研究——不同涂层的碳钢/海水界面生物膜初探

 海洋微型污损生物膜会影响金属腐蚀过程和防污涂料性能,是污损生物群落的初级食物链,一直是国内外的研究焦点。研究了冬季青岛中港海水中暴露100余天的碳钢表面形成的腐蚀产物膜,以及载玻片、HT防腐涂层和NFGP600防污涂层表面形成的生物膜,采用电化学技术研究材料表面生物膜特征,运用SEM、EDS、XRD表征生物膜形态和物质组成,分析生物膜细菌、硅藻和原生动物的种类及形貌。研究表明,生物膜由细菌、硅藻、原生动物和海水中无机、有机颗粒组成;钢/海水界面同时发生钢的腐蚀和微型生物附着过程,两个过程互相作用使碳钢表面形成不定型、松软、不连续的腐蚀产物膜;防腐涂层表面生物膜由于原生动物对菌藻的蚕食和碳酸盐的存在,形成了较为疏松的生物膜,而防污涂层表面没有原生动物的影响,形成了致密的生物膜,在一定程度上能够隔绝海水环境。     

Effect of Juglone against Pseudomonas syringae pv Actinidiae Planktonic Growth and Biofilm Formation

Pseudomonas syringaepv Actinidiae (P. syringae) is a common pathogen causing plant diseases. Limoli proved that its strong pathogenicity is closely related to biofilm state. As a natural bacteriostatic agent with broad-spectrum bactericidal properties, juglone can be used as a substitute for synthetic bacteriostatic agents. To explore the antibacterial mechanism, this study was carried out to examine the inhibitory effect of juglone on cell membrane destruction, abnormal oxidative stress, DNA insertion and biofilm prevention of P. syringae. Results showed that juglone at 20 μg/mL can act against planktogenic P. syringae (10⁷ CFU/mL). Specially, the application of juglone significantly damaged the permeability and integrity of the cell membrane of P. syringae. Additionally, juglone caused abnormal intracellular oxidative stress, and also embedded in genomic DNA, which affected the normal function of the DNA of P. syringae. In addition, environmental scanning electron microscope (ESEM) and other methods showed that juglone effectively restricted the production of extracellular polymers, and then affected the formation of the cell membrane. This study provided a possibility for the development and utilization of natural juglone in plants, especially P. syringae.     

聚丙烯酸对自然水体生物膜吸附镉的影响

选择聚丙烯酸(PAA)为水中溶解态高分子天然有机质的代表, 研究了PAA对自然水体生物膜吸附重金属Cd的影响, 包括不同浓度的PAA对吸附的影响, PAA对特定pH下吸附等温线的影响以及不同pH下按不同顺序添加PAA时对吸附的影响. 研究结果表明, PAA的存在一般会降低生物膜对Cd的吸附, 其影响程度与PAA的浓度、 溶液pH、 吸附顺序及生物膜厚度等有关. PAA与Cd的浓度比越高, 其对吸附的影响越显著. 吸附溶液pH越高, PAA的影响越显著. 吸附顺序对吸附的影响在pH较低时不明显, 当pH较高时, 先加PAA后加Cd及两者同时吸附时对吸附的降低作用接近且较大, 先加Cd后加PAA时对吸附的降低作用相对较小. 生物膜较薄时PAA的影响更显著. PAA对生物膜吸附Cd的影响主要由PAA与生物膜之间对Cd的竞争以及三元表面配合物的生成与吸附2种因素共同决定. 高pH会促进PAA与Cd的配合而不利于带负电的配合物在生物膜上的吸附.     

厌氧-好氧反应器处理选矿废水的挂膜实验

 选矿废水中所含的选矿药剂种类多,毒性大,物质结构复杂,大多难以被微生物快速、有效利用,进入环境后可以长期存留,用物化法难以保证出水中有机浮选药剂长期稳定达标排放,因此用生物法处理选矿废水达标排放或便于回收利用已势在必行。本实验采用逐渐增加进水的选矿药剂浓度、固定水力停留时间的方法启动厌氧-好氧反应器,分析了其挂膜过程中对COD和浮选药剂浓度的去除效果及生物相的变化情况。结果表明,挂膜和驯化期间,系统对COD的去除主要集中在好氧反应器,厌氧反应器虽也有一定的去除效果,但去除率远远低于好氧反应器。反应器启动40d后,COD的总去除率稳定在55%,苯胺黑药、乙硫氮和丁基黄药的总去除率分别达到92%,84%和82%,且填料中的生物相趋于稳定,标志着系统挂膜成功。     

蜂窝陶瓷载体生物膜工艺的除磷试验

分别采用序批式生物膜反应器（SBBR）和A／O工艺进行比较,利用蜂窝陶瓷作为生物膜载体。分别处理模拟的受严重污染的地表水．重点研究磷的去除规律及影响因素,实验结果表明：厌氧时间为2．5h,好氧时间为6h;进水COD／TP为50—60,从SBBR出水中,磷浓度小于0．5mg·L^-1,总磷去除率大于85％,而A／O工艺的除磷率不到50％．     

生物接触氧化工艺用填料的生物膜特性

为阐明不同类型填料对生物膜的影响,选取弹性立体填料、组合式填料、多面空心球作为接触氧化池的填料,通过考察挥发性生物膜量、生物膜耗氧率、生物膜多聚糖等指标,研究填料的挂膜效果与生物膜特性.结果表明：弹性立体填料挂膜速度较慢,约为8天左右,组合式填料与多面空心球挂膜速度相当;组合填料上的生物膜对于底物有较高去除率,约为90%,生物膜量高;多面空心球受气水作用能够悬浮转动,因而具有较强的布水、布气功能,生物膜活性较高,但生物膜容易脱落导致系统受负荷冲击时生物量流失而处理效果变差;弹性填料具有处理效果稳定,受环境变化影响较小,且便于反冲洗,因此其综合性能较好.