Propolis-Based Nanofiber Patches to Repair Corneal Microbial Keratitis

In this research, polyvinyl-alcohol (PVA)/gelatin (GEL)/propolis (Ps) biocompatible nanofiber patches were fabricated via electrospinning technique. The controlled release of Propolis, surface wettability behaviors, antimicrobial activities against the S. aureus and P. aeruginosa, and biocompatibility properties with the mesenchymal stem cells (MSCs) were investigated in detail. By adding 0.5, 1, and 3 wt.% GEL into the 13 wt.% PVA, the morphological and mechanical results suggested that 13 wt.% PVA/0.5 wt.% GEL patch can be an ideal matrix for 3 and 5 wt.% propolis addition. Morphological results revealed that the diameters of the electrospun nanofiber patches were increased with GEL (from 290 nm to 400 nm) and Ps addition and crosslinking process cause the formation of thicker nanofibers. The tensile strength and elongation at break enhancement were also determined for 13 wt.% PVA/0.5 wt.% GEL/3 wt.% Ps patch. Propolis was released quickly in the first hour and arrived at a plateau. Cell culture and contact angle results confirmed that the 3 wt.% addition of propolis reinforced mesenchymal stem cell proliferation and wettability properties of the patches. The antimicrobial activity demonstrated that propolis loaded patches had antibacterial activity against the S. aureus, but for P. aeruginosa, more studies should be performed.     

Antibacterial Activity of Ciprofloxacin-Loaded Poly(lactic-co-glycolic acid)-Nanoparticles Against Staphylococcus aureus

The formation of bacterial biofilms on material surfaces is a recurrent problem in public health. Antibacterial nanoparticles (NPs) are promising because pathogens have not yet developed resistance mechanisms and encapsulation of the drug can protect it from the surrounding medium and improve pharmacokinetics. Biocompatible and biodegradable particles of various sizes (nano- and micro-scale) based on poly(lactic-co-glycolic acid) (PLGA) are elaborated using a simple and free toxic nanoprecipitation process. Particles are poly(ethylene glycol) (PEG)-ylated in order to reduce unwanted interactions with biological fluids, or loaded with the large spectrum antibiotic ciprofloxacin (CIP). NPs are studied against Staphylococcus aureus in planktonic and biofilm modes. Empty NPs with smallest size (60 nm) are able to totally eradicate planktonic culture after 24 h, even in the presence of serum proteins. CIP-loaded NPs present slightly lower antimicrobial activity against planktonic microorganisms compared with the free antibiotic, due to progressive release of CIP over time. In biofilm mode, CIP-loaded NPs show a very good antibiofilm activity, much better than free CIP, thanks to NPs penetration within the polymer matrix and a consequent release of the antibiotic close to the embedded bacteria. The present results open the way for widespread applications of PLGA-NPs in the pharmaceutical or medical fields.     

Investigating dysregulated pathways in Staphylococcus aureus (SA) exposed macrophages based on pathway interaction network

ObjectiveThis work aimed to identify dysregulated pathways for Staphylococcus aureus (SA) exposed macrophages based on pathway interaction network (PIN).MethodsThe inference of dysregulated pathways was comprised of four steps: preparing gene expression data, protein–protein interaction (PPI) data and pathway data; constructing a PIN dependent on the data and Pearson correlation coefficient (PCC); selecting seed pathway from PIN by computing activity score for each pathway according to principal component analysis (PCA) method; and investigating dysregulated pathways in a minimum set of pathways (MSP) utilizing seed pathway and the area under the receiver operating characteristics curve (AUC) index implemented in support vector machines (SVM) model.ResultsA total of 20,545 genes, 449,833 interactions and 1189 pathways were obtained in the gene expression data, PPI data and pathway data, respectively. The PIN was consisted of 8388 interactions and 1189 nodes, and Respiratory electron transport, ATP synthesis by chemiosmotic coupling, and heat production by uncoupling proteins was identified as the seed pathway. Finally, 15 dysregulated pathways in MSP (AUC = 0.999) were obtained for SA infected samples, such as Respiratory electron transport and DNA Replication.ConclusionsWe have identified 15 dysregulated pathways for SA infected macrophages based on PIN. The findings might provide potential biomarkers for early detection and therapy of SA infection, and give insights to reveal the molecular mechanism underlying SA infections. However, how these dysregulated pathways worked together still needs to be studied.     

Antibacterial mode of action of 1,8-dihydroxy-anthraquinone from Porphyra haitanensis against Staphylococcus aureus

As one kind of anthraquinone dihydroxy derivatives, 1,8-dihydroxy-anthraquinone (Dan) with strong antibacterial activity against Staphylococcus aureus was first isolated from Porphyra haitanensis. Here, we report on the investigation of the antibacterial mode of action of Dan on the Gram-positive bacterium S. aureus. The results show that Dan strongly inhibited cell growth at logarithmic phase. In this study, the antibacterial activity of Dan was analysed by using phosphorus standard solution, p-nitrophenyl phosphate, o-nitrophenyl-β-d-galactopyanoside, scanning electron microscopy and transmission electron microscopy. The results suggested that the antibacterial activity of Dan is due to its interaction with the cell wall and cell membrane, by which it increases the permeability of the cell envelope and leads to the leakage of cytoplasm and the deconstruction of cell. This study indicates that Dan as a natural product in seaweeds deserves further investigation for applications as an antibacterial bioactive substance in food safety control and drugs.     

4种常用除草剂对玉米、绿豆和萝卜的影响

采用非靶标植物影响试验的土壤处理法,分别测定500 g·L-1莠灭净悬浮剂、400 g·L-1二甲戊灵乳油、56%二甲四氯钠可溶粉剂和900 g·L-12,4-滴异辛酯乳油4种玉米田常用除草剂对玉米、绿豆和萝卜的半效应浓度EC50(14 d),并进行影响评价,以明确除草剂对玉米及非靶标植物的安全性。结果显示,500 g·L-1莠灭净悬浮剂、400 g·L-1二甲戊灵乳油、56%二甲四氯钠可溶粉剂和900 g·L-12,4-滴异辛酯乳油对玉米和绿豆均为低毒,400 g·L-1二甲戊灵乳油对萝卜为低毒,500 g·L-1莠灭净悬浮剂、56%二甲四氯钠可溶粉剂对萝卜为中毒,900 g·L-12,4-滴异辛酯乳油对萝卜为高毒。4种除草剂均可按照推荐剂量施用于玉米田,但在选择施用500 g·L-1莠灭净悬浮剂、56%二甲四氯钠可溶粉剂和900 g·L-12,4-滴异辛酯乳油时,应避免间、套种萝卜并远离萝卜田,以免对萝卜造成药害。     

利用Fura-2/AM荧光探针法和LCSM法研究受磁场处理S.aureus细胞Ca2+的跨膜行为

研究受脉冲磁场处理金黄色葡萄球菌(S.aureus)细胞Ca2+的跨膜行为,为此研究了表征S.aureus胞内Ca2+浓度变化Fura-2/AM荧光探针检测法,并检测了不同脉冲数下经脉冲磁场处理后S.aureus细胞荧光强度的变化,采用激光共聚焦扫描显微镜(LCSM)观察了经脉冲磁场处理前后S.aureus胞内Ca2+浓度的变化。研究结果表明,Fura-2/AM可成功的负载于S.aureus中,可以应用于S.aureus胞内游离钙离子浓度变化的测定。经脉冲磁场处理后,S.aureus胞内钙离子浓度显著上升,且与活菌数的减少高度相关,相关度达到-0.989 15;胞内光点显著增多,光点荧光强度明显增大,说明大量胞外钙离子跨膜进入胞内。因此,可以判断微生物细胞膜通透性的改变和胞内Ca2+浓度的上升是高强度脉冲磁场具有杀菌作用的重要原因。     

大气压低温等离子体的活性氧成分分析及其杀菌效应研究

系统分析了以Ar+O₂ (2%)为气源, 以直流辉光放电方式激发的大气压低温等离子体中的活性氧(ROS)成分及其杀菌的生物学效应。采用电子自旋共振(ESR)等技术方法, 对等离子体的ROS成分进行了检测分析, 同时采用低温等离子体在水下作用的方式探究了其对金黄色葡萄球菌的杀灭作用。通过电子自旋共振分析, 直接检测出两种活性氧自由基, 分别是羟自由基(OH?)和单线态氧(¹O₂), 间接证明了超氧阴离子(O₂^-?)的存在。同时用臭氧检测仪等对O₃和H₂O₂等进行了定量分析。等离子体能有效杀灭金黄色葡萄球菌, 10分钟杀菌率能达到99.9%。 低温等离子体中含有大量的ROS成分, 并能有效杀灭金黄色葡萄球菌, 可能的杀菌机制是ROS成分诱导细菌细胞内脂质、蛋白质、DNA等过氧化。研究结果提示大气压低温等离子体在临床医学研究中具有潜在的巨大应用价值。     

利用表面活性剂介导的方法制备AgrC蛋白脂质体

膜蛋白AgrC是金黄色葡萄球菌双组分信号转导系统的感受激酶. 其信号转导机制的阐明对于解决细菌耐药问题具有重要意义. 目前膜蛋白研究的主要瓶颈是难以获得大量高纯度和功能稳定的蛋白. 将目标蛋白表达在大肠杆菌体内,利用表面活性剂将其从细胞膜上溶解,纯化,这一系列步骤容易引起膜蛋白不稳定和功能损失. 本文报道了用表面活性剂介导的方法将膜蛋白AgrC镶嵌到脂质体上,即形成蛋白脂质体. 脂质体和蛋白脂质体的结构、形貌以及平均粒径分别用透射电镜和动态光散射仪表征. 蔗糖密度梯度离心的结果表明蛋白重构效率达80%. 硫醇试剂标记实验确定AgrC的细胞质域在脂质体中取向于内侧. 体外磷酸化实验表明AgrC蛋白在脂质体中的自我磷酸化活性远远高于表面活性剂中的活性,且其自我磷酸化活性在2周内几乎没有损失. 蛋白脂质体的构建不仅解决了膜蛋白的不稳定性问题,也为体外研究AgrC蛋白的结构、功能和信号转导机制提供了新的思路.     

3-(2-羟基-4,6-二甲氧基苯基)-5-芳基异噁唑啉的合成及抑菌活性

以查尔酮衍生物为前体, 与盐酸羟胺在碱性条件下反应制得7个3-(2-羟基-4,6-二甲氧基苯基)-5-芳基异噁唑啉化合物(2a~2g), 产物经红外光谱、核磁共振谱、质谱和元素分析表征. 抑菌活性研究结果表明, 化合物2d和2e对大肠杆菌、金黄色葡萄球菌、枯草杆菌和绿脓杆菌均有一定抑制作用, 其中化合物2e对大肠杆菌、金黄色葡萄球菌表现出极好的抑菌活性.     

Unexpected Enhancement of Antimicrobial Polymer Activity against Staphylococcus aureus in the Presence of Fetal Bovine Serum

Cationic and amphiphilic polymers are known to exert broad-spectrum antibacterial activity by a putative mechanism of membrane disruption. Typically, nonspecific binding to hydrophobic components of the complex biological milieu, such as globular proteins, is considered a deterrent to the successful application of such polymers. To evaluate the extent to which serum deactivates antibacterial polymethacrylates, we compared their minimum inhibitory concentrations in the presence and absence of fetal bovine serum. Surprisingly, we discovered that the addition of fetal bovine serum (FBS) to the assay media in fact enhances the antimicrobial activity of polymers against Gram-positive bacteria S. aureus, whereas the opposite is the case for Gram-negative E. coli. Here, we present these unexpected trends and develop a hypothesis to potentially explain this unusual phenomenon.