Structure–Activity Relationship Assessment of Sophorolipid Ester Derivatives against Model Bacteria Strains

Sophorolipids (SLs) are glycolipids that consist of a hydrophilic sophorose head group covalently linked to a hydrophobic fatty acid tail. They are produced by fermentation of non-pathogenic yeasts such as Candida Bombicola. The fermentation products predominantly consist of the diacetylated lactonic form that coexists with the open-chain acidic form. A systematic series of modified SLs were prepared by ring opening of natural lactonic SL with n-alkanols of varying chain length under alkaline conditions and lipase-selective acetylation of sophorose primary hydroxyl groups. The antimicrobial activity of modified SLs against Gram-positive human pathogens was a function of the n-alkanol length, as well as the degree of sophorose acetylation at the primary hydroxyl sites. Modified SLs were identified with promising antimicrobial activities against Gram-positive human pathogens with moderate selectivity (therapeutic index, TI = EC₅₀/MIC_{B. cereus} = 6–33). SL-butyl ester exhibited the best antimicrobial activity (MIC = 12 μM) and selectivity (TI = 33) among all SLs tested. Kinetic studies revealed that SL-ester derivatives kill B. cereus in a time-dependent manner resulting in greater than a 3-log reduction in cell number within 1 h at 2×MIC. In contrast, lactonic SL required 3 h to achieve the same efficiency.     

褐煤SHELL气化飞灰黏附影响因素的研究

通过激光粒度仪、X射线荧光光谱仪、扫描电子显微镜等现代化分析测试技术对褐煤样、飞灰样以及换热废锅中的积灰样进行了粒度分布、化学组成、晶体矿物组成、微观形貌、微区化学组成等特征的分析,研究影响飞灰黏附特性的因素。并通过引入富集系数,描述各个元素在煤灰、正常飞灰、废锅积灰中的迁移富集情况。结果表明,在废锅积灰中有含铁矿物的生成,同时Na、K、Fe、S、P元素在废锅积灰中发生富集,在飞灰与积灰颗粒边缘处有大量的Fe、Na元素的富集。     

聚砜共价键合磷铵两性离子的结构修饰及其血液相容性的研究

利用形成碳-氧键将磷铵两性离子(1)共价键合到聚砜(PSF)材料表面,改善其抗凝血性能.首先对聚砜(PSF)进行氯甲基化反应,生成苄氯结构,然后通过自合成两性离子化合物1中的—OH与氯甲基化聚砜的—CH2Cl反应形成醚键,将两性离子结构接枝在PSF上.用ATR-FTIR、EA和1H-NMR表征了产物结构,并通过水接触角、溶血实验和血小板黏附实验对结构修饰前后材料的亲水性和抗凝血性能进行了比较.改性PSF材料的表面亲水性提高,几种改性PSF材料的溶血率均低于5%,PSF-18.1%1材料的表面几乎没有血小板黏附.结果表明,磷铵两性离子结构修饰的聚砜材料可以显著提高其血液相容性,在血液相容性材料等领域具有潜在的应用价值.     

Design and evaluation of a real-time activity probe for focal adhesion kinase

Focal adhesion kinase (FAK) has been identified as a potential therapeutic target for the treatment of metastatic cancers. Herein we describe the design, synthesis and optimization of a direct activity sensor for FAK and its application to screening FAK inhibitors. We find that the position of the sensing moiety, a phosphorylation-sensitive sulfonamido-oxine fluorophore, can dramatically influence the performance of peptide sensors for FAK. Real-time fluorescence activity assays using an optimized sensor construct, termed FAKtide-S2, are highly reproducible (Z' = 0.91) and are capable of detecting as little as 1 nM recombinant FAK. Utilizing this robust assay format, we define conditions for the screening of FAK inhibitors and demonstrate the utility of this platform using a set of well-characterized small molecule kinase inhibitors. Additionally, we provide the selectivity profile of FAKtide-S2 among a panel of closely related enzymes, identifying conditions for selectively monitoring FAK activity in the presence of off-target enzymes. In the long term, the chemosensor platform described in this work can be used to identify novel FAK inhibitor scaffolds and potentially assess the efficacy of FAK inhibitors in disease models.     

仿生沉积法制备水下低气体黏附透明材料

透明材料常用于水下设备中,而聚合物透明材料多较为疏水,在水下易黏附气泡,影响其光学性能.利用多巴胺(DA)和聚乙烯亚胺(PEI)共沉积技术,在多种透明聚合物材料表面构建了亲水/水下超疏气涂层.结果表明,聚多巴胺(PDA)与PEI可通过Michael加成或Schiff碱反应在此类材料表面形成亲水交联网络,显著提高其表面亲水性.表现为水接触角显著降低,而水下气接触角显著提高(140?),气泡在材料表面的黏附力显著下降.沉积时间在6 h以下时,XPS和椭圆偏振测试的结果表明,虽然所选用的透明材料表面沉积量和沉积厚度随时间有所上升,但其透光性不会受到显著影响.该方法具有较强的普适性,可用于多种水下气体黏附性较强的透明高分子材料,如聚苯乙烯(PS)、聚对苯二甲酸乙二醇酯(PET)、聚甲基丙烯酸甲酯(PMMA)、聚丙烯(PP)和聚酰亚胺(PI)等.同时,该方法形成的涂层的长期稳定性也较好,材料在水中浸泡振荡10天之后仍能保持较好的抗气泡黏附能力.该方法适用于如潜水艇舷窗、护目镜、水下光学镜头及其防护罩等水下设备中.     

致病菌与糖的特异性识别及其分析应用研究

致病菌往往通过凝集素-糖特异性识别来实现对宿主细胞的粘附,进而感染宿主组织,引起病变。因此,研究致病菌与糖的特异性识别有利于进一步了解感染性疾病的致病机制,为致病菌的特异性检测和感染性疾病的治疗提供新的策略。该文总结了致病菌-糖特异性识别的相关机制机理;介绍了目前主要的研究方法和技术,特别评述了荧光光谱、表面等离子体共振、电化学阻抗谱及石英晶体微天平等技术在该研究中的应用现状,并对这4种技术与微流控芯片平台的结合进行了探讨;针对致病菌检测特异性差、耐药性严重等难题,重点综述了致病菌-糖的特异性识别在细菌分离、富集、检测、鉴别、生物膜抑制及抗菌糖类药物筛选方面的应用。最后对致病菌-糖特异性识别基础和应用研究进行了展望。     

Electrochemical Determination of Neomycin and Norfloxacin at a Novel Polymer Nanocomposite Electrode in Aqueous Solution

Organic compounds such as antibiotics that are not effectively removed by modern-day treatment technology are a growing threat to water quality and health. The emergence of antibiotics in the aquatic environment is a matter of concern as they may induce bacterial resistance, a major threat to health-care management and an increasing economic crisis. The current methods that are used to detect antibiotics are expensive and time consuming due to the sample preparation necessary for the determination of low concentrations of antibiotics in water and the instruments used. Electrochemical sensors and biosensors are simple systems, with high selectivity and sensitivity for individual measurements and low cost. In this study, we present a novel polyamic acid/graphene oxide electrode that was prepared for electrochemical screening of selected antibiotic residues in aqueous solution. Polyamic acid and graphene oxide were synthesized independently and characterized using microscopic, spectroscopic, and voltammetric approaches. A polyamic acid/graphene oxide/screen-sprinted carbon electrode was prepared in situ by electrochemical deposition of polyamic acid/graphene (0.03?mg/mL 50:50 mass ratio) on screen-printed carbon electrodes using five cycles between ?1000 and 1000?mV at 50?mV/s. The polyamic acid/graphene oxide/screen-printed carbon electrode provided limits of detection of 0.034?µM for norfloxacin and 1.07?µM for neomycin. Recovery studies on synthetic urine showed good inter-day and intra-day coefficients of variation (n?=?3).     

Dissecting Molecular Aspects of Cell Interactions Using Glycodendrimersomes with Programmable Glycan Presentation and Engineered Human Lectins

Glycodendrimersomes with programmable surface display of glycan, together with artificially engineered galectins, were used to understand the physiological significance of human lectins with homodimeric and tandem‐repeat‐type displays. The mode of topological surface presentation and the density of glycan affected vesicle aggregation mediated by multivalent carbohydrate–protein interactions. The cross‐linking capacity of homodimeric lectins was enhanced by covalent connection of the two carbohydrate‐binding sites. These findings highlight the value of glycodendrimersomes as versatile cell membrane mimetics, and assays provide diagnostic tools for protein functionality. This work also provides guidelines for the design of cell separators, bioactive matrices, bioeffectors, and other biomedical applications.     

Morphological and mechanical properties of tannic acid/PAAm semi-IPN hydrogels for cell adhesion

A series of hydrogels were fabricated from tannic acid (TA), a typical plant polyphenol widely present in wood, and polyacrylamide (PAAm) by semi-IPN and cryogelation techniques. The introduction of TA into the PAAm network endows the system with enhanced cell adhesion properties. The cryogels with open interconnected macropores had a superfast swelling rate and a high swelling ratio, as well as high elasticity in response to compression. The degradation of the hydrogels can be tuned by modulating the content of cross-linker poly(ethylene glycol) diacrylate (PEGDA). Cytotoxicity results revealed that the hydrogels were non-toxic to COS-7 cells. All these results suggested that TA/PAAm semi-IPN hydrogels have great potential for applications in tissue engineering.     

Collagen-based scaffolds enriched with glycosaminoglycans isolated from skin of Salmo salar fish

In this study both collagen and glycosaminoglycans were isolated from biodegradable waste. Namely collagen was isolated from rat tail tendons and glycosaminoglycans (GAGs) from fish skin. Porous materials were then obtained based on the isolated collagen with 1 or 5% addition of GAGs by freeze-drying process. The scaffolds were studied by infrared spectroscopy, mechanical testing and examined for the porosity and density. The scaffolds structure was observed by scanning electron microscope. The adhesion and proliferation of human osteosarcoma SaOS-2 cells was examined on prepared scaffolds to assess their biocompability.The results showed that the addition of glycosaminoglycans improves the properties of collagen-based scaffolds. Mechanical strength was increased by GAGs addition as well as the porosity of studied materials. Each scaffold with and without GAGs displayed porous structure with interconnected regular shaped pores. The attachment of cells was better for pure collagen scaffold, however, GAGs additive promoted the cells proliferation on the scaffold.