Few-layer V2C/MWCNT with high ionic accessibility for lithium-ion storage.

A V2C MXene has a high theoretical capacity and low diffusion barrier, showing tremendous potential in lithium-ion batteries. However, most reports on V2C focus on a multilayered structure that is stacked, which diminishes the ionic accessibility and results in unsatisfactory cycling stability. Therefore, we synthesized a few-layer V2C (f-V2C) material and added multi-walled carbon nanotubes (MWCNTs). The formed f-V2C/MWCNT provides abundant pores, which enhance ionic accessibility, so that Li+ can easily enter the layer space. The introduction of MWCNTs can further separate the f-V2C, expand the specific surface area, reduce the charge transfer resistance, and heighten the structural stability. The experiments reveal that f-V2C/MWCNT has a high specific capacity of 531 mA h g-1 at 0.1 A g-1 after 100 cycles. Even at a high current density of 5.0 A g-1, the specific capacity can still reach 166 mA h g-1. Moreover, the f-V2C/MWCNT structure shows good cycling stability with a capacity retention rate of 95% after 1000 cycles at 5.0 A g-1. The above findings indicate that f-V2C/MWCNT has great application potential in the field of Li+ storage.

WS2 nanosheets vertically grown on Ti3C2 as superior anodes for lithium-ion batteries.

Tungsten disulfide (WS2) is considered as a promising anode material for high-performance lithium-ion batteries (LIBs) result from its inherent characteristics such as high theoretical capacity, large interlayer spacing and weak interlayer Van der Waals force. Nevertheless, WS2 has the drawbacks of easy agglomeration, severe volume expansion and high Li+ migration barrier, which lead to rapid capacity degradation and imperfect rate ability. In this work, a novel two-dimensional (2D) hierarchical composite (Ti3C2/WS2) consisting of WS2 nanosheets vertically grown on titanium carbide (Ti3C2) nanosheets is prepared. Thanks to this distinctive hierarchical structure and synergy between WS2 and Ti3C2, the Ti3C2/WS2 composite demonstrates exceptional electrochemical performance in LIBs. In addition, we investigate the effect of the mass proportion of WS2 in Ti3C2/WS2 composite on the electrochemical performance, and find that the optimal mass ratio of WS2 is 60%. As expected, the optimal electrode exhibits a high specific capacity (650 mAh/g at 0.1 A/g after 100 cycles) and ultra-long cycle stability (400 mAh/g at 1.0 A/g after 5000 cycles).

Understanding ammonia and nitrous oxide formation in typical three-way catalysis during the catalyst warm-up period.

Ammonia (NH3) and nitrous oxide (N2O) have been regarded as the typical secondary pollutants emitted from vehicles equipped with a three-way catalyst (TWC). MultiGas FT-IR Analyzer was applied to determine the outlet gas concentrations in the light-off experiments, in order to understand how different reaction conditions and catalyst aging affect the production of these two pollutants. It was found that N2O formation is favored by the existence of excess oxygen during NO reduction, whereas NH3 is readily formed within the lack of reactive oxygen species. Interestingly, the reduction of NO by H2 in presence of excess oxygen can also lead to NH3 formation when the active metal particles are large enough, which provides the rational explanation why the increased NH3 was emitted from older gasoline vehicles. The loss of the catalytically active sites and reducibility caused by thermal aging requires longer time to warm-up thereby favors the N2O and NH3 formation, which is the major reason for the higher CO, NOx, HC, N2O and NH3 emissions from the old gasoline vehicles than that of low-mileage gasoline vehicles.

Habitat association in the critically endangered Mangshan pit viper (Protobothrops mangshanensis), a species endemic to China.

Habitat directly affects the population size and geographical distribution of wildlife species, including the Mangshan pit viper (Protobothrops mangshanensis), a critically endangered snake species endemic to China. We searched for Mangshan pit viper using randomly arranged transects in their area of distribution and assessed their habitat association using plots, with the goals of gaining a better understanding of the habitat features associated with P. mangshanensis detection and determining if the association with these features varies across season. We conducted transect surveys, found 48 individual snakes, and measured 11 habitat variables seasonally in used and random plots in Hunan Mangshan National Nature Reserve over a period of 5 years (2012-2016). The important habitat variables for predicting Mangshan pit viper detection were fallen log density, shrub density, leaf litter cover, herb cover and distance to water. In spring, summer and autumn, Mangshan pit viper detection was always positively associated with fallen log density. In summer, Mangshan pit viper detection was related to such habitats with high canopy cover, high shrub density and high herb cover. In autumn, snakes generally occurred in habitats near water in areas with high fallen log density and tall shrubs height. Our study is the first to demonstrate the relationship between Mangshan pit viper detection and specific habitat components. Mangshan pit viper detection was associated with habitat features such as with a relatively high fallen log density and shrub density, moderately high leaf litter cover, sites near stream, and with lower herb cover. The pattern of the relationship between snakes and habitats was not consistent across the seasons. Identifying the habitat features associated with Mangshan pit viper detection can better inform the forestry department on managing natural reserves to meet the habitat requirements for this critically endangered snake species.

Mechanisms of transcellular transport of wheat germ agglutinin-functionalized polymeric nanoparticles in Caco-2 cells.

Transcellular transport is essential for transmucosal and plasma-to-tissue drug delivery by nanoparticles, whereas its fundamental pathways have not been fully clarified. In this study, an in-depth investigation was conducted into the intracellular itinerary and the transcytosis pathway of wheat germ agglutinin-functionalized nanoparticles (WGA-NP) with various polymer architectures in the Caco-2 cell model. GFP-Rabs, Rab4, Rab5, Rab7, Rab11, GTPases served as key regulators of vesicular transport, and their mutants were transfected to Caco-2 cells respectively to determine the cellular itinerary of WGA-NP and the role of Rabs therein. Transcytosis inhibition experiments indicated that transcellular transport of WGA-NP (PEG(3000)-PLA(40000) formulation) happened in a cytoskeleton-dependent manner and majorly by means of clathrin-mediated mechanism. Intracellular transport, especially the endolysosome pathway was found largely contribute to the transcytosis of WGA-NP. WGA-NP with shorter surface PEG length (2000) resulted in higher cellular association and more colocalization with the clathrin-mediated transport pathway, while that with longer surface PEG length (5000) avoided the clathrin-mediated transport pathway but achieved higher transcytosis after 4 h incubation. WGA-NP with PLGA as the core materials obtained elevated lysosome escape and enhanced transcytosis after 2 h incubation. These findings provided important evidence for the role of polymer architectures in modulating cellular transport of functionalized nanocarriers, and would be helpful in improving carrier design to enhance drug delivery.

Effect of lactoferrin- and transferrin-conjugated polymersomes in brain targeting: in vitro and in vivo evaluations.

AIM: To evaluate the effect of lactoferrin (Lf) and transferrin (Tf) in brain targeting. METHODS: Polymersomes (PSs), employed as vectors, were conjugated with Lf or Tf and were characterized by morphology, particle size, zeta potential, and surface densities of the Lf or Tf molecules. In vitro uptake of Lf-PS and Tf-PS by bEnd.3 cells was investigated using coumarin-6 as a fluorescent probe. In vivo tissue distribution and pharmacokinetics of (125)I-Lf-PS and (125)I-Tf-PS were also examined. RESULTS: The mean particle size of PS, Lf-PS, and Tf-PS was around 150 nm and the zeta potential of the PSs was about -20 mV. Less than 0.12% of the coumarin was released from coumarin-6-loaded PS in 84 h indicating that coumarin-6 was an accurate probe for the PSs' behavior in vitro. It was shown that the uptake of Lf-PS and Tf-PS by bEnd.3 cells was time-, temperature-, and concentration-dependent. Both Lf and Tf could increase the cell uptake of PSs at 37 degrees C, but the uptake of Tf-PS was significantly greater than that of Lf-PS. In vivo tissue distribution and pharmacokinetics in mice revealed higher brain uptake and distribution of Tf-PS than Lf-PS, which was in accordance with in vitro uptake results. The drug targeting index (DTI) of Tf-PS with regard to Lf-PS was 1.51. CONCLUSION: Using a PS as the delivery vector and bEnd.3 cells as the model of the blood-brain barrier (BBB), Tf was more effective than Lf in brain targeting.

Quantum dots for tracking cellular transport of lectin-functionalized nanoparticles.

Successful drug delivery by functionalized nanocarriers largely depends on their efficient intracellular transport which has not yet been fully understood. We developed a new tracking technique by encapsulating quantum dots into the core of wheat germ agglutinin-conjugated nanoparticles (WGA-NP) to track cellular transport of functionalized nanocarriers. The resulting nanoparticles showed no changes in particle size, zeta potential or biobinding activity, and the loaded probe presented excellent photostability and tracking ability. Taking advantage of these properties, cellular transport profiles of WGA-NP in Caco-2 cells was demonstrated. The cellular uptake begins with binding of WGA to its receptor at the cell surface. The subsequent endocytosis happened in a cytoskeleton-dependent manner and by means of clathrin and caveolae-mediated mechanisms. After endosome creating, transport occurs to both trans-Golgi and lysosome. Our study provides new evidences for quantum dots as a cellular tracking probe of nanocarriers and helps understand intracellular transport profile of lectin-functionalized nanoparticles.

Quantum dots bearing lectin-functionalized nanoparticles as a platform for in vivo brain imaging.

Delivery of imaging agents to the brain is highly important for the diagnosis and treatment of central nervous system (CNS) diseases, as well as the elucidation of their pathophysiology. Quantum dots (QDs) provide a novel probe with unique physical, chemical, and optical properties, and become a promising tool for in vivo molecular and cellular imaging. However, their poor stability and low blood-brain barrier permeability severely limit their ability to enter into and act on their target sites in the CNS following parenteral administration. Here, we developed a QDs-based imaging platform for brain imaging by incorporating QDs into the core of poly(ethylene glycol)-poly(lactic acid) nanoparticles, which was then functionalized with wheat germ agglutinin and delivered into the brain via nasal application. The resulting nanoparticles, with high payload capacity, are water-soluble, stable, and showed excellent and safe brain targeting and imaging properties. With PEG functional terminal groups available on the nanoparticles surface, this nanoprobe allows for conjugation of various biological ligands, holding considerable potential for the development of specific imaging agents for various CNS diseases.

Odorranalectin is a small peptide lectin with potential for drug delivery and targeting.

BACKGROUND: Lectins are sugar-binding proteins that specifically recognize sugar complexes. Based on the specificity of protein-sugar interactions, different lectins could be used as carrier molecules to target drugs specifically to different cells which express different glycan arrays. In spite of lectin's interesting biological potential for drug targeting and delivery, a potential disadvantage of natural lectins may be large size molecules that results in immunogenicity and toxicity. Smaller peptides which can mimic the function of lectins are promising candidates for drug targeting. PRINCIPAL FINDINGS: Small peptide with lectin-like behavior was screened from amphibian skin secretions and its structure and function were studied by NMR, NMR-titration, SPR and mutant analysis. A lectin-like peptide named odorranalectin was identified from skin secretions of Odorrana grahami. It was composed of 17 aa with a sequence of YASPKCFRYPNGVLACT. L-fucose could specifically inhibit the haemagglutination induced by odorranalectin. (125)I-odorranalectin was stable in mice plasma. In experimental mouse models, odorranalectin was proved to mainly conjugate to liver, spleen and lung after i.v. administration. Odorranalectin showed extremely low toxicity and immunogenicity in mice. The small size and single disulfide bridge of odorranalectin make it easy to manipulate for developing as a drug targeting system. The cyclic peptide of odorranalectin disclosed by solution NMR study adopts a beta-turn conformation stabilized by one intramolecular disulfide bond between Cys6-Cys16 and three hydrogen bonds between Phe7-Ala15, Tyr9-Val13, Tyr9-Gly12. Residues K5, C6, F7, C16 and T17 consist of the binding site of L-fucose on odorranalectin determined by NMR titration and mutant analysis. The structure of odorranalectin in bound form is more stable than in free form. CONCLUSION: These findings identify the smallest lectin so far, and show the application potential of odorranalectin for drug delivery and targeting. It also disclosed a new strategy of amphibian anti-infection.

Brain delivery of vasoactive intestinal peptide enhanced with the nanoparticles conjugated with wheat germ agglutinin following intranasal administration.

The development of biotech drugs such as peptides and proteins that act in the central nervous system has been significantly impeded by the difficulty of delivering them across the blood-brain barrier. The surface engineering of nanoparticles with lectins opened a novel pathway to the absorption of drugs loaded by biodegradable poly (ethylene glycol)-poly (lactic acid) nanoparticles in the brain following intranasal administration. In the present study, vasoactive intestinal peptide, a neuroprotective peptide, was efficiently incorporated into the poly (ethylene glycol)-poly (lactic acid) nanoparticles modified with wheat germ agglutinin and the biodistribution, brain uptake and neuroprotective effect of the formulation were assessed. The area under the concentration-time curve of intact 125I-vasoactive intestinal peptide in brain of mice following the intranasal administration of 125I-vasoactive intestinal peptide carried by nanoparticles and wheat germ agglutinin-conjugated ones was significantly enlarged by 3.5 approximately 4.7 folds and 5.6 approximately 7.7 folds, respectively, compared with that after intranasal application of 125I-vasoactive intestinal peptide solution. The same improvements in spatial memory in ethylcholine aziridium-treated rats were observed following intranasal administration of 25 microg/kg and 12.5 microg/kg of vasoactive intestinal peptide loaded by unmodified nanoparticles and wheat germ agglutinin-modified nanoparticles, respectively. Distribution profiles of wheat germ agglutinin-conjugated nanoparticles in the nasal cavity presented their higher affinity to the olfactory mucosa than to the respiratory one. Inhibition experiment with specific sugars suggested that the interaction between the nasal mucosa and the wheat germ agglutinin-functionalized nanoparticles were due to the immobilization of carbohydrate-binding pockets on the surface of the nanoparticles. The results clearly indicated wheat germ agglutinin-modified nanoparticles might serve as promising carriers especially for biotech drugs such as peptides and proteins.