Highly biocompatible and recyclable biomimetic nanoparticles for antibiotic-resistant bacteria infection.

Increasing number of resistant bacteria have emerged with the overuse of antibiotics, which indicates that the bacterial infection has become a global challenge. Furthermore, the pollution of antibiotics to the environment has become a serious threat to public health. It is known that toxins produced by bacteria are the main cause of bacterial infections. Photothermal therapy is an effective antibacterial approach. However, the photothermal reagents cannot eliminate bacterial toxins, and even some anti-bacterial materials are toxic. Here, we synthesized a biomimetic recycled nanoparticle, red blood cell (RBC) membrane-coated Fe3O4 nanoparticles (RBC@Fe3O4), as an antibacterial agent. The RBC@Fe3O4 nanoparticles act as nano-sponges to trap toxins and then kill them all with a photothermal effect. We can describe this process simply as a battle between two armies. Our strategy is to disarm the "enemy" so that we can easily kill the "enemy" who has no power, which results in enhancing the bactericidal efficacy. The toxin of methicillin-resistant Staphylococcus aureus (MRSA) was absorbed by RBC@Fe3O4in vitro. In addition, in vivo studies proved that the RBC@Fe3O4 nanoparticles confer obvious survival benefits against toxin-induced lethality by absorbing the toxin of MRSA. Furthermore, using a mouse model of MRSA wound infection, the RBC@Fe3O4 nanoparticles with laser irradiation were found to have a superior wound-healing effect. Simultaneously, the RBC@Fe3O4 nanoparticles could be recycled in a simple way without affecting the bactericidal efficacy. The highly biocompatible and recyclable RBC@Fe3O4 biomimetic nanoparticles based on photothermal therapy and bacterial toxin adsorption strategy are promising for treating bacterial infections.

[Difference in nitrogen accumulation and translocation between semi-winterness and springness wheat.] / æ˜¥æ€§å’ŒåŠå†¬æ€§å°éº¦æ¤æ ªæ°®ç´ ç§¯ç´¯ä¸Žè¿è½¬ç‰¹å¾å·®å¼‚.

Nitrogen accumulation, translocation and allocation were investigated in a field experiment to find out the difference between six semi-winterness wheat cultivars and nine springness wheat cultivars that are mainly grown in Jiangsu. Results indicated that the average nitrogen accumulation amount (NAA) in the semi-winterness wheat cultivars was lower from the beginning of wintering to jointing stage, but higher from booting to maturity stage, compared with the springness wheat cultivars tested under the same rate of nitrogen fertilization. The amount of nitrogen accumulated between the beginning of wintering and jointing stage showed no significant difference between the two types of wheat cultivars, but that accumulated between anthesis and maturity in the semi-winterness wheat cultivars was higher than that in the springness wheat cultivars. The total N translocation amount (TNTA) and N accumulation amount to grains after anthesis (NAAA) were significantly higher in the semi-winterness wheat cultivars than those in the springness wheat cultivars, but the total N translocation efficiency (NTE), the contribution proportion of accumulated N (ANCP), and the contribution proportion of translocated N (TNCP) did not show significant difference between the two types of wheat cultivars. In leaves, the semi-winterness wheat cultivars showed lower TNTA, NTE and TNCP than the springness wheat cultivars, but in stem and sheath these N indexes were higher in the semi-winterness wheat cultivars, with a significant level for TNTA. These were significant differences in NAA, NAAA, TNTA and TNCP among cultivars with the same spring type or semi-winter type. According to the differences in nitrogen absorption, utilization and translocation among different wheat cultivars, nitrogen utilization efficiency could be improved by using approp-riate amount and reasonable proportion of nitrogen fertilizers at different developmental stages of wheat.

[Changes of endogenous hormone contents and antioxidative enzyme activities in wheat leaves under low temperature stress at jointing stage].

Low temperature stresses (-3 and -5 °C) were simulated using artificial temperature-controlled phytotrons to study the freezing rate, the contents of endogenous hormones, and the activities of antioxidative enzymes in the leaves of wheat plants of Yangmai 16 (YM 16) and Xumai 30 (XM 30) at jointing stage. The grade and index of freezing injury increased with lower temperature and longer stress. The freezing rate was at the 5th level and the main stems and tillers of both cultivars were finally dead under -5 °C lasting for 72 h. On the last day of stress initiation, the contents of abscisic acid (ABA) and zeatin riboside (ZR), and the activities of superoxide dismutase (SOD), peroxide dismutase (POD), and catalase (CAT) in leaves increased at the beginning and then declined as low temperature progressed. On the 3rd day after stress, the contents of ABA and ZR and the activities of antioxidative enzymes were higher than those on the last day of cold stress, and then reduced to the level of the control on the 6th day after stress. The content of gibberellins (GA3) was lowered by cold stress. For YM 16, GA3 content increased from the 3rd day to the 6th day after cold stress, whereas, for XM 30, it increased first and then decreased. For the treatment of -5 °C lasting for 72 h, the contents of hormones and the activities of antioxidative enzymes were significantly lower than those of the other treatments. Correlation analyses showed that higher ABA and ZR contents, and higher SOD, POD and CAT activities as well as lower GA3 content could alleviate the low-temperature injury in wheat plants under low temperature stress.

Assessment of the AquaCrop model for use in simulation of irrigated winter wheat canopy cover, biomass, and grain yield in the North China Plain.

Improving winter wheat water use efficiency in the North China Plain (NCP), China is essential in light of current irrigation water shortages. In this study, the AquaCrop model was used to calibrate, and validate winter wheat crop performance under various planting dates and irrigation application rates. All experiments were conducted at the Xiaotangshan experimental site in Beijing, China, during seasons of 2008/2009, 2009/2010, 2010/2011 and 2011/2012. This model was first calibrated using data from 2008/2009 and 2009/2010, and subsequently validated using data from 2010/2011 and 2011/2012. The results showed that the simulated canopy cover (CC), biomass yield (BY) and grain yield (GY) were consistent with the measured CC, BY and GY, with corresponding coefficients of determination (R(2)) of 0.93, 0.91 and 0.93, respectively. In addition, relationships between BY, GY and transpiration (T), (R(2) = 0.57 and 0.71, respectively) was observed. These results suggest that frequent irrigation with a small amount of water significantly improved BY and GY. Collectively, these results indicate that the AquaCrop model can be used in the evaluation of various winter wheat irrigation strategies. The AquaCrop model predicted winter wheat CC, BY and GY with acceptable accuracy. Therefore, we concluded that AquaCrop is a useful decision-making tool for use in efforts to optimize wheat winter planting dates, and irrigation strategies.

[Effects of ozone pollution on the accumulation and distribution of dry matter and biomass carbon of different varieties of wheat].

Effects of surface ozone pollution on the terrestrial ecosystem and plant growth have drawn great attention. With the support of the free-air ozone concentration enrichment (O3-FACE) system located in Jiangdu City, Jiangsu Province, the effects of elevated atmospheric ozone (pO3) on the accumulation and distribution of dry matter and biomass carbon as well as the C/N ratio of crop residue of five wheat (Tritcium aestivum L.) varieties (Yangmai 15, Yangmai 16, Yannong 19, Yangfumai 2 and Jiaxing 002) were investigated in the Yangtze River delta, the target pO3 of which was 50% higher than the ambient pO3. The results showed that the accumulation and distribution of different wheat varieties responded differently to elevated pO3. Elevated pO3 decreased the biomass of Yangmai 15 and Jiaxing 002, increased the Yangfumai 2 biomass, and had no effects on the total biomass of Yangmai 16 and Yannog 19, among which a significant difference was found for Jiaxing 002. Elevated pO3 significantly increased the ratios of root to shoot for Yangmai 15 and Jiaxing 002 and significantly decreased the root/shoot ratios of Yannong 19 and Yangfumai 2, but had no effect on Yangmai 16, leading to an obvious difference in dry matter distributed among aboveground and belowground parts. O3 enrichment decreased the wheatear weight of Yangmai 15, Yangmai 16 and Jiaxing 002, and had no effect on that of Yannong 19 and Yangfumai 2. Elevated pO3 significantly decreased the proportion of grain weight to ear weight by 8.2%-15.5% for Jiaxing 002, Yannong 19 and Yangfumai 2, whereas the proportion was increased for Yangmai 15 and not affected for Yangmai 16, suggesting that O3 enrichment lead to different decreases in the yield of Jiaxing 002, Yannong 19, Yangfumai 2 and Yangmai 16. Elevated pO3 significantly increased the straw carbon of Yannong 19 and Yanfumai 2 by 14.1%-22.9% and significantly decreased the straw C/N ratio by 10.9%-29.1%. The rising pO3 significantly decreased the straw carbon of Jiaxing 002 and significantly increased the straw C/N ratio. Moreover, for Yangmai 16 and Yangmai 15, there was a decreasing straw carbon amount and an increasing straw C/N under rising pO3. Elevated pO3 significantly decreased the carbon quantity and C/N of root residue in Yangmai 16, Yannong 19 and Yangfumai 2. Elevated pO3 had not significant effect on the root residue carbon of Jiaxing 002, but significantly decreased its C/N ratio. However, elevated pO3 had no effect on the quantity and quality of the root residue of Yangmai 15. It is obvious that when evaluating the response of the formation and distribution of wheat dry matter and the quantity and quality of root and straw carbon to O3 pollution, the difference in wheat varieties should be taken into account.

[Effects of elevated atmospheric ozone concentration on flag leaf photosynthetic pigment contents of wheat].

By using a free-air controlled enrichment (FACE) system, this paper studied the effects of elevated atmospheric ozone (O3) concentration (150% of ambient O3) on the flag leaf photosynthetic pigment contents of wheat varieties Yannong 19, Yangmai 16, Jiaxin 002, Yangmai 15, and Yangfumai 2. For the test varieties, no significant differences were observed in the flag leaf chlorophyll a, chlorophyll b, chlorophyll (a+b), and carotenoid contents between treatments elevated O3 concentration and ambient O3 at booting and anthesis stages, but the photosynthetic pigment contents in treatment elevated O3 concentration all decreased after anthesis, with a significant decrease of chlorophyll a, chlorophyll b, and chlorophyll (a+b) contents, which indicated that elevated O3 had minor effects on the synthesis of photosynthetic pigments but accelerated their decline process. Different wheat varieties had genetic difference in the responses of flag leaf photosynthetic pigment contents to elevated O3, among which, Yangmai 15 and Jiaxin 002 had better tolerance to ozone stress. The flag leaf chlorophyll a, chlorophyll b, and chlorophyll (a+b) contents at grain-filling stage (about 21 days after anthesis) had a significant positive correlation with the 1000-grain mass.

[Impacts of elevated atmospheric ozone concentration on flag leaf microscopic structure of wheat: a field study with FACE system].

By using FACE (Free-Air Controlled Environment)-ozone system, a field plot experiment was conducted in 2008-2009 to study the effects of elevated ozone (O3) concentration on the flag leaf microscopic structure, chlorophyll content, and grain weight of wheat. Two treatments were installed, i. e., ambient O3 and 150% of ambient O3, and four winter varieties, i. e., Yannong 19, Yangmai 16, Jiaxin 002, and Yangfumai 2, were taken as the test materials. At anthesis, elevated O3 concentration had a slight damage to the flag leaf microscopic structure. The mesophyll cell and chloroplast structure began destroying, and the grana lamellae started breaking and loosing. Twenty-one days after anthesis, the differences in the leaf microscopic structure between the two treatments became significant. Under elevated O3, the flag leaf senescence was accelerated, with the endomembrane system disintegrated, grana lamella disappeared, and corpus adiposum inside chloroplast broken down, resulting in a significant decrease of the chlorophyll content, photosynthesis rate, and grain weight at maturing stage. Significant difference was observed among the test varieties in their responses to elevated O3. Jiaxin 002 was tolerant, while Yangfumai 2 was sensitive to the ozone stress.

[Hyperspectral estimation of leaf water content for winter wheat based on grey relational analysis (GRA)].

The objective of the present study was to compare two methods for the precision of estimating leaf water content (LWC) in winter wheat by combining stepwise regression method and partial least squares (SRM-PLS) or PLS based on the relational degree of grey relational analysis (GRA) between water vegetation indexes (WVIs) and LWC. Firstly, data utilized to analyze the grey relationships between LWC and the selected typical WVIs were used to determine the sensitivity of different WVIs to LWC. Secondly, the two methods of estimating LWC in winter wheat were compared, one was to directly use PLS and the other was to combine SRM and PLS, and then the method with the highest determination coefficient (R2) and lowest root mean square error (RMSE) was selected to estimate LWC in winter wheat. The results showed that the relationships between the first five WVI and LWC were stable by using GRA, and then LWC was estimated by using PLS and SRM-PLS at the whole stages with the R2 and RMSEs being 0.605 and 0.575, 4.75% and 7.35%, respectively. The results indicated that the estimation accuracy of LWC could be improved by using GRA firstly and then by using PLS and SRM-PLS.

[Effects of elevated ozone concentration on wheat grain protein components with FACE system].

In 2006-2009, a Free-Air Controlled Enrichment (FACE) system was applied to study the effects of elevated ozone concentration ([O3]) on the grain protein components and their dynamics of four winter wheat varieties Yannong 19, Yangmai 16, Yangmai 15, and Yangfumai 2. Two levels of [O3] were installed, i. e., ambient level (CK-O3) and 50% higher than the ambient level (E-O3). With the increase of [O3], the grain protein content of the varieties increased, with the increment being 7.55% - 16.37% (2006 - 2007), 4.93% - 22.63% (2007 - 2008), and 2.29% - 17.65% (2008 - 2009) in the three years, respectively, and the differences between treatments, varieties, and years being all significant. Adversely, the grain protein yield was decreased significantly by 1.83% - 11.64% (2006 - 2007), - 0.41% - 24.22% (2007 - 2008), and -1.90% - 15.81% (2008 - 2009), respectively in the three years. The contents of four grain protein components (albumin, globulin, gliadin, and glutenin) were significantly higher under E-O3 than under CK-O3, and the differences between treatments, varieties, and years were significant, except the albumin and glutenin contents between treatments.