Antibacterial activities of hexadecanoic acid methyl ester and green-synthesized silver nanoparticles against multidrug-resistant bacteria

Antibacterial drug resistance is considered one of the biggest threats to human health worldwide, and the overuse of antibiotics accelerates this problem. Multidrug-resistant (MDR) bacteria are becoming harder to treat as the antibiotics used to treat them become less effective. Therefore, it is necessary to evaluate novel methods to control MDR bacteria. In this study, 40 bacterial isolates were collected from diabetic patients. The sensitivity of 40 bacterial isolates to seven antibiotics was evaluated. Four bacterial isolates were resistant to all antibiotic groups. The MDR pathogenic bacteria were selected and identified morphologically and biochemically and confirmed by VITEK® 2 system as follows: Staphylococcus aureus W35, Pseudomonas aeruginosa D31, Klebsiella pneumoniae DF30, and K. pneumoniae B40. Identification of the most resistant P. aeruginosa D31 was confirmed by the sequencing of a 16S ribosomal RNA gene with an accession number (MW241596). The inhibitory activity of eight types of native grown plant extracts against MDR bacteria was studied. Clove alcoholic extract (CAE) showed the highest inhibitory activity against MDR bacteria. Gas chromatography–mass spectrometry analysis of partially purified CAE at 0.9 Rf detected by thin-layer chromatography showed an active compound named hexadecenoic acid methyl ester with the highest antimicrobial effect against clinical pathogenic bacteria. The formation of silver nanoparticles (AgNPs) by CAE was studied. Evaluation of AgNPs was investigated by X-ray diffraction, UV–Vis, and transmission electron microscopy. The antibacterial effect of AgNPs after 2, 4, and 6 days in light and dark conditions was evaluated. Finally, the AgNPs synthesized using CAE possess good inhibition activity against the tested pathogenic bacteria. As a result, the bactericidal components listed above were promising in reducing MDR bacteria and can be used for treatments of bacterial infection and in the development of safe products with a natural base.     

Magnetic Polymer/Nickel Hybrid Nanoparticles Via Miniemulsion Polymerization

This work shows a method to synthesize and encapsulate magnetic nickel nanocrystals into polymeric colloidal particles through miniemulsion polymerization. The nickel nanoparticles are produced by a thermal decomposition method in the presence of oleylamine and triphenylphosphine, which results in a hydrophobic surface. However, being compatible with the monomer does not ensure a successful encapsulation by miniemulsion polymerization, as the nickel nanoparticles are expelled from the polymer particles with increasing styrene conversion due to the poor adhesion interaction between the organic shells of the nickel nanoparticles and the polystyrene. Changing the hydrophobic polystyrene to a polymer with higher polarity such as poly(methyl methacrylate) proves to be efficient for encapsulation of nickel nanoparticles when employing a hydrophilic initiator. After encapsulation, these nanoparticles show magnetic response.

     

Concentration Fluctuations and Segmental Dynamics in Weakly Dynamic Asymmetric Blends in the Presence of Surface‐Functionalized Multiwall Carbon Nanotubes

Surface‐functionalized multiwall carbon nanotubes (MWCNTs) are incorporated in poly(methyl methacrylate)/styrene acrylonitrile (PMMA/SAN) blends and the pretransitional regime is monitored in situ by melt rheology and dielectric spectroscopy. As the blends exhibit weak dynamic asymmetry, the obvious transitions in the melt rheology due to thermal concentration fluctuations are weak. This is further supported by the weak temperature dependence of the correlation length (ξ ≈ 10–12 Å) in the vicinity of demixing. Hence, various rheological techniques in both the temperature and frequency domains are adopted to evaluate the demixing temperature. The spinodal decomposition temperature is manifested in an increase in the miscibility gap in the presence of MWCNTs. Furthermore, MWCNTs lead to a significant slowdown of the segmental dynamics in the blends. Thermally induced phase separation in the PMMA/SAN blends lead to selective localization of MWCNTs in the PMMA phase. This further manifests itself in a significant increase in the melt conductivity.

     

Investigations into the Mass Spectrometric Method for the Determination of the Mode of Termination in Radical Polymerization

The fraction of termination by disproportionation, λ, in radical polymerization may be determined by a mass spectrometric (MS) analysis of the resulting polymer. It is subjected to an array of stringent consistency checks, working with polymerizations of methyl methacrylate at 85 °C in three different solvents and with four different initiators. λ is shown to be unaffected by the choice of initiator, initiator concentration, or isoviscous solvent. These findings serve to allay any fears about the method being undermined by effects such as primary radical termination or chain transfer to solvent, thereby establishing its robustness. At the same time, direct evidence for the occurrence of chain transfer to the solvent methyl isobutyrate is uncovered, and the importance of knowing other rate‐parameter values accurately, if λ is to be determined accurately, is illustrated. By carrying out MS analyses, it is concluded that electrospray ionization with time‐of‐flight detection gives the best results for the present purpose.

     

LC-QQQ-MS/MS分析苯磺酸氨氯地平中痕量苯磺酸酯类基因毒性杂质

摘要：目的 建立LC-QQQ-MS/MS分析测定苯磺酸氨氯地平中痕量苯磺酸酯类基因毒性杂质苯磺酸甲酯、苯磺酸乙酯、苯磺酸丙酯和苯磺酸异丙酯的检测方法。方法 采用Agilent Zorbax SB-C18（3.0mm×100mm,1.8μm）色谱柱,以水（含 5mMol?L-1甲酸铵和0.1%甲酸）和甲醇（含5mMol?L-1甲酸铵和0.1%甲酸）为流动相,梯度洗脱,流速0.4 mL?min-1,电喷雾离子化（ESI）,正离子模式下MRM采集。结果 苯磺酸甲酯定量限为20 ng?mL-1,苯磺酸乙酯、苯磺酸丙酯和苯磺酸异丙酯定量限为1 ng·mL-1;方法精密度良好,保留时间和峰面积RSD%均小于5%（n=10）;苯磺酸甲酯在20~1000ng·mL-1,苯磺酸乙酯、苯磺酸丙酯和苯磺酸异丙酯在1~1000ng?mL-1的浓度范围内呈良好的线性关系,r≥0.998;方法准确度良好,平均加标回收率（n=10）分别为99.77%、100.19%、94.21%和92.43%。5个不同厂家生产的苯磺酸氨氯地平中苯磺酸甲酯的含量均小于LOQ（8μg?g-1）,苯磺酸乙酯、苯磺酸丙酯和苯磺酸异丙酯的含量均小于LOQ（0.4μg?g-1）。结论 该方法可用于苯磺酸氨氯地平中痕量基因毒性杂质苯磺酸甲酯、苯磺酸乙酯、苯磺酸丙酯和苯磺酸异丙酯含量的检测分析。     

Hesperidin protects testicular and spermatological damages induced by cisplatin in rats

The clinic usage of cisplatin, an anticancer drug, is limited due to it has many side effects in many systems and organs. In this context, it was aimed to investigate the protective effect of hesperidin, a citrus flavonoid, on testicular and spermatological damages induced by cisplatin in rats. The rats were randomly divided into four groups. The first group was kept as a control. In the second groups, cisplatin was given at the single dose of 7 mg kg^?1 intraperitoneally. In the third group, hesperidin was orally administered at the dose of 50 mg/kg day^?1 for 14 days. In the fourth group, cisplatin and hesperidin were given together at the same doses. Cisplatin treatment caused significant reductions enzymatic (SOD, CAT and GPx) and nonenzymatic (GSH) antioxidants and significant induction level of TBARS. In addition, cisplatin treatment caused decreased sperm motility, epididymal sperm concentration, increased abnormal sperm rate and histopathological damage. In contrast, hesperidin treatment significantly attenuated the harmful effects. In conclusion, this study clearly demonstrated that hesperidin has protective effects on cisplatin‐induced reproductive system toxicity depending on its antioxidant properties. Thus, it is thought that hesperidin may be useful against cisplatin toxicity in patients with cancer in terms of reproductive system.     

Involvement of epigenetics and microRNA-29b in the urethane induced inception and establishment of mouse lung tumors

Epigenetic changes are correlated with tumor development showing aberrations in DNA methylation and histone modifications. To find the early changes, we evaluated the epigenetic events from early to late stage of the urethane induced lung tumor development in mouse model and tried to correlate the molecular events with the progression of tumor. We addressed the hypothesis by examining the tumor development, status of DNMTs, HDACs and MBDs, DNA methylation and expression of microRNA-29b during 1 to 36 weeks after urethane exposure that included the period before and after the tumor appearance. Tumors did not appear after 1 or 4 weeks but well defined tumors appeared after 12 weeks and larger tumors appeared at 36 weeks which was prevented by IP6. DNMT1, DNMT3a and DNMT3b were upregulated after urethane exposure at the time of no tumor till the tumor developed and showed its upregulated functional activity. DNMTs are shown to be the targets of microRNA-29b and we showed that microRNA-29b was downregulated in the line of DNMT upregulation. HDAC, the histone modifier, also showed progressive upregulation. Periodic increase in methyl binding proteins, MBD2, supported the expression of gene silencing pathways in terms of the downregulation of tumor suppressor genes, p16 and MLH1. All these molecular alterations were protected in the presence of IP6. Our results showed that the key steps of epigenetics, DNMTs, mir29b, and HDAC1, are altered both before and after the development of tumors.     

Recent progress in allosteric modulators for GluN2A subunit and development of GluN2A‐selective nuclear imaging probes

N‐methyl‐D‐aspartate (NMDA) receptors play key roles in physiology by regulating the synaptic plasticity and the cellular mechanism involved in learning and memory. The GluN2A subunit is the most abundant expression of NMDA receptors in mature brain, and its dysfunction has been implicated in various neurological disorders. However, the function of GluN2A subunit in physiological and pathological conditions is not yet completely unveil due to the lack of subunit‐selective ligands, including specific positron emission tomography (PET)/single photon emission computed tomography (SPECT) imaging probes. In this review, recent progresses in understanding its pathophysiological role, the structure‐activity relationship, and the postulated mechanisms of novel GluN2A ligands as well as status of molecular imaging probes for PET are summarized.