Highly bright and photostable cyanine dye-doped silica nanoparticles for optical imaging: Photophysical characterization and cell tests

Spherical silica nanoparticles containing fluorescent trimethine indocyanine dyes (λ_abs = 547 nm, λ_em = 570 nm) were prepared using a water-in-oil microemulsion method. The nanoparticles were of 50 nm diameter and were almost monodispersed in aqueous solution at pH 5.5. Entrapment of dye molecules in the silica matrix stabilised photoemission over several hours of continuous irradiation. The photoemission intensity of the indocyanine was increased 13-fold over that recorded in solution. As each nanoparticle contained 110 dye molecules, the photoemission brightness of each particle was enhanced by three orders of magnitude. The fluorescent nanoparticles have been tested as imaging tools in in vitro tests. As an example of non-macrophagic cells, a highly differentiated neuronal cell line (GT1-7) was used and the results showed that the prepared nanoparticles can be incorporated into these cells with no apparent toxicity for up to three days.     

设计院培训工作的实践与思考

人才是企业发展的财富。人才的培训在企业发展过程中发挥着重要作用。以自主创新为核心,把提高专业技术人员的整体素质与创造和谐企业相结合,创新培训模式、优化培训项目,健全培训制度和培训体系,提高培训效益,不断拓展培训的深度和广度。     

Earthworm coelomocytes as nanoscavenger of ZnO NPs

Earthworms can ‘biotransform’ or ‘biodegrade’ chemical contaminants, rendering them harmless in their bodies, and can bioaccumulate them in their tissues. They ‘absorb’ the dissolved chemicals through their moist ‘body wall’ due to the interstitial water and also ingest by ‘mouth’ while soil passes through the gut. Since the advent of the nanotechnology era, the environmental sink has been continuously receiving engineered nanomaterials as well as their derivatives. Our current understanding of the potential impact of nanomaterials and their natural scavenger is limited. In the present investigation, we studied the cellular uptake of ZnO nanoparticles (NPs) by coelomocytes especially by chloragocytes of Eisenia fetida and their role as nanoscavenger. Results from exposure to 100- and 50-nm ZnO NPs indicate that coelomocytes of the earthworm E. fetida show no significant DNA damage at a dose lower than 3 mg/l and have the potential ability to uptake ZnO NPs from the soil ecosystem and transform them into microparticles.     

Internalization of Salmonella enterica by tomato fruit

Since 1990, several outbreaks of foodborne illness have been associated with the consumption of raw tomatoes. Various serovars of the bacterial pathogen, Salmonella enterica, were responsible for these illnesses. Fruits and vegetables are not a normal niche for mammalian pathogens. Hypotheses concerning introduction of Salmonella into tomatoes range from contamination in the field or greenhouse to direct or cross-contamination during harvest, handling and preparation of tomato as a raw agricultural commodity. Many different reports have shown that Salmonella can not only survive in tomato fruit but also proliferate from small, relatively inconsequential populations to numbers known to incite illness even in healthy individuals.Herein, production, harvest and handling of fresh market tomatoes are evaluated in terms of how Salmonella might contaminate this crop. Physical principles are emphasized, whereas biological factors are included where appropriate. Salmonella is viewed as a bacterium that is affected by the same physical principles affecting bacteria naturally occurring in the environment surrounding tomato fruit as well as tomato plants during production, harvest and handling.     

青蒿琥酯增加小鼠腹腔巨噬细胞内化内毒素、大肠埃希菌的作用及可能机制

目的: 观察青蒿琥酯(artesunate, AS)对小鼠腹腔巨噬细胞内化清除脂多糖/内毒素(lipopolysaccharide/endotoxin, LPS)和吞噬大肠埃希菌的影响,并初步探讨其可能的作用机制。方法: MTT法检测不同浓度网格蛋白抑制剂(monodansylcadaverine, MDC)、内体酸化抑制剂氯喹(chloroquine, CQ)对小鼠腹腔巨噬细胞活力的影响,以选择恰当的药物工作浓度;激光共聚焦法检测青蒿琥酯及MDC、CQ对小鼠腹腔巨噬细胞内化FITC-LPS的影响;分别采用激光共聚焦和菌落集落形成计数实验观察青蒿琥酯对小鼠腹腔巨噬细胞内化大肠埃希菌的影响;逆转录PCR检测青蒿琥酯对小鼠腹腔巨噬细胞清道夫受体A(class A scavenger receptor,SR-A) mRNA表达的影响。结果: MDC和CQ浓度分别小于 25 μg/mL 和 20 μg/mL 时对小鼠腹腔巨噬细胞活力无影响;MDC、CQ可抑制小鼠腹腔巨噬细胞内化LPS,青蒿琥酯可增加小鼠腹腔巨噬细胞对LPS的内化,而且青蒿琥酯可增加MDC和CQ处理的巨噬细胞内化LPS的功能。激光共聚焦和菌落集落形成计数实验均显示青蒿琥酯可增加小鼠腹腔巨噬细胞对大肠埃希菌的内化能力。逆转录PCR结果显示青蒿琥酯可增强LPS处理或未处理的小鼠腹腔巨噬细胞SR-A mRNA的表达。结论: 青蒿琥酯可增强小鼠腹腔巨噬细胞内化LPS、大肠埃希菌的能力,该作用可能与SR-A mRNA表达升高有关。     

浅析教育者在思想政治教育内化和外化中的作用

思想政治教育内化与外化是受教育者思想政治素质变化发展的重要阶段,而在这一过程中,教育者的教育力量发挥了十分重要的作用。教育者遵循内化外化过程的发展规律及思想政治教育过程发展规律,实现教育者自身的转化,再依据实际情况确定内化切入点,通过理性启迪与非理性引导、是非判断与价值判断相结合、受教育者自我意识分化与同一等途径,促使受教育者的思想政治素质向社会所需要的方向转化。     

油气田企业环境内化管理的组织与控制机制研究

通过强化油气田企业自身在环境管理过程中的责任意识,可以有效减低油气资源开发过程对周边生态环境产生的影响。为此我们提出了"环境内化管理"的思想,把环境保护的外在要求内化到企业常规管理中,形成环境保护的自我要求、习惯和责任意识;油气田企业需要对环境内化管理设置目标、制定内化管理制度;以交流协作、制度审查、运作维护为环节来保证环境内化管理的组织;以责任机制、信息披露机制、内部环境系统考评机制、应急预案处理机制等来保证环境问题内化管理的有效实施。     

A microwire sensor for rapid detection of Escherichia coli K-12 in fresh produce

A rapid immunofluorescence method for foodborne pathogens in food systems using microwire sensor coupled with high frequency alternating current was developed. The method was intended to enrich and quantify E. coli cells internalized in baby spinach leaves. The targeted bacterial cells in the sample solution were captured on microwires in a diameter of 25 μm, and were bound to fluorescein isothiocyanate (FITC) labeled polyclonal E. coli antibodies. Fluorescent images of the FITC antibodies were obtained using a fluorescence microscope equipped with a charge-coupled-device (CCD) camera, and the fluorescent intensity (FI) was quantified through image processing. The capture of E. coli K-12 in PBS buffer was optimized when the electric field was generated at the frequency of 3 MHz and 20 Vpp with bacterial concentration of 10⁷ CFU/mL. The detection limit of our sensing device was determined to be 10³ CFU/mL. Field emission scanning electron microscopy (FESEM) was used to validate and visualize E. coli cells captured on the tip surface. The sensitivity and specificity of the developed sensor has been successfully validated by testing E. coli internalized in baby spinach leaves. The immunofluorescence detection has been completed within 15 min. Moreover, it was found that the enrichment process of E. coli cells using the dielectrophoretic force was rarely affected by food particles, which proved the sensing selectivity. The developed sensor is expected to meet the steady demand for a simple, rapid, highly sensitive detection approach to quantify the targeted microbes in food systems.

Industrial Relevance

There has been an increase in the number of foodborne illnesses linked to the consumption of fresh and minimally processed fruits and vegetables. Some E.coli strains such as E.coli O 157:H7, can cause a variety of diseases, including diarrhea, urinary tract infections, respiratory diseases, meningitis and more. In general, consumers wash the fresh produces under cold running tap water to remove any lingering dirt on the surface of the produces before eating or preparing. However, how do the consumers know if there is any possible pathogen hiding inside of the fresh produce after rinsing? It was reported from many researchers that, the E.coli internalization, which may occur when fresh produces intake E. coli containing water or manure from the soil, would be a main cause of the foodborne illness outbreak. To ensure the safety of drinking water, E.coli concentration cannot be higher than 1 CFU/mL. How can we detect such a low level of E.coli in an easy yet efficient way? To our knowledge, none of the traditional detecting approaches such as cultural based method, polymerase chain reaction(PCR), surface plasmon resonance (SPR) biosensor, and Latex Agglutination, has performed perfectly. Hence, a rapid and accurate technique for detecting foodborne pathogens in fresh produce is urgently needed in order to secure the food safety.To overcome this issue, a simple detection method for foodborne pathogens in food systems using the microwire sensor coupled with high frequency alternative current was developed. The sensitivity and specificity of the developed sensor have been successfully validated by testing with E. coli internalized inside baby spinach leaves. It was found that spinach particles rarely affect the performance of our sensing device, which shows a promising prospect of its application in food industries.     

Distribution of Salmonella typhimurium in romaine lettuce leaves

Leafy greens are occasionally involved in outbreaks of enteric pathogens. In order to control the plant contamination it is necessary to understand the factors that influence enteric pathogen-plant interactions. Attachment of Salmonella enterica serovar typhimurium to lettuce leaves has been demonstrated before; however, only limited information is available regarding the localization and distribution of immigrant Salmonella on the leaf surface. To extend our knowledge regarding initial pathogen-leaf interactions, the distribution of green-fluorescent protein-labeled Salmonella typhimurium on artificially contaminated romaine lettuce leaves was analyzed. We demonstrate that attachment of Salmonella to different leaf regions is highly variable; yet a higher attachment level was observed on leaf regions localized close to the petiole (7.7 log CFU g⁻¹) compared to surfaces at the far-end region of the leaf blade (6.2 log CFU g⁻¹). Attachment to surfaces located at a central leaf region demonstrated intermediate attachment level (7.0 log CFU g⁻¹). Salmonella displayed higher affinity toward the abaxial side compared to the adaxial side of the same leaf region. Rarely, Salmonella cells were also visualized underneath stomata within the parenchymal tissue, supporting the notion that this pathogen can also internalize romaine lettuce leaves. Comparison of attachment to leaves of different ages showed that Salmonella displayed higher affinity to older compared to younger leaves (1.5 log). Scanning electron microscopy revealed a more complex topography on the surface of older leaves, as well as on the abaxial side of the examined leaf tissue supporting the notion that a higher attachment level might be correlated with a more composite leaf landscape. Our findings indicate that initial attachment of Salmonella to romaine lettuce leaf depends on multiple plant factors pertaining to the specific localization on the leaf tissue and to the developmental stage of the leaf.     

Salmonella Typhimurium internalization is variable in leafy vegetables and fresh herbs

Despite washing and decontamination, outbreaks linked to consumption of fresh or minimally-processed leafy greens have been increasingly reported in recent years. In order to assure the safety of produce it is necessary to gain knowledge regarding the exact routes of contamination. Leaf internalization through stomata was previously reported as a potential route of contamination, which renders food-borne pathogens protected from washing and disinfection by sanitizers. In the present study we have examined the incidence (percentage of microscopic fields harboring ≥ 1 GFP-tagged bacteria) of Salmonella Typhimurium on the surface and underneath the epidermis in detached leaves of seven vegetables and fresh herbs. The incidence of internalized Salmonella varied considerably among the different plants. The highest incidence was observed in iceberg lettuce (81 ± 16%) and arugula leaves (88 ± 16%), while romaine (16 ± 16%) and red-lettuce (20 ± 15%), showed significantly lower incidence (P < 0.05). Internalization incidence in fresh basil was 46 ± 12%, while parsley and tomato leaves demonstrated only marginal internalization (1.9 ± 3.3% and 0.56 ± 1.36%, respectively). Internalization of Salmonella in iceberg lettuce largely varied (0-100%) through a 2 year survey, with a higher incidence occurring mainly in the summer. These results imply that Salmonella internalization occurs in several leafy vegetables and fresh herbs, other than iceberg lettuce, yet the level of internalization largely varies among plants and within the same crop. Since internalized bacteria may evade disinfection, it is of great interest to identify plants which are more susceptible to bacterial internalization, as well as plant and environmental factors that affect internalization.