A simulation study on the self-assembly of rod-coil-rod triblock copolymers within nanoslits.

Self-assembly of rod-coil-rod R4C12R4 triblock copolymers within a nanoslit is investigated by using dissipative particle dynamics simulations. Perpendicular lamellae (L⊥) in nonselective or weak selective slits and parallel lamellae (L∥) in coil-selective slits are observed, and both are almost independent of the slit thickness. However, in the rod-selective slits, the assembled structures are strongly dependent on the slit thickness. With an increase in the slit thickness, we sequentially observe hexagonally packed cylinders (HC) of rod blocks perpendicular to surfaces in thin slits, parallel wavy lamellae, orderly packed alternating cylinders in moderate slits, a mixture structure of HC near surfaces and L⊥ in the interior region, and finally L∥ in wide slits. Our simulation results reveal that the rod block and surface properties play an important role in the assembly of confined rod-coil-rod triblock copolymers. Results also illustrate the competition between the slit thickness and the length scale of lamellae in bulk for the confined copolymers in nanoslits.

Toxic effects of microplastics and nitrite exposure on intestinal histology, digestion, immunity, and microbial community of shrimp Litopenaeus vannamei.

Nitrite and microplastics (MPs) are environmental pollutants that threaten intestinal integrity and affect immune function of shrimp. In this study, the shrimp Litopenaeus vannamei were exposed to the individual and combined stress of nitrite and microplastics for 14 days, and the changes of intestinal histology and physiological functions were investigated. After single and combined stress, affectations occurred in intestinal tissue; the antioxidant enzyme activities (MDA, H2O2, CAT increased) and gene expression levels (CAT, SOD, GPx, HSP70 up-regulated) changed. The expression levels of detoxification genes (CYP450, UGT down-regulated, GST up-regulated), apoptosis genes (CASP-3 up-regulated) and endoplasmic reticulum stress genes (Bip, GRP94 down-regulated) changed. Furthermore, the stress also increased intestinal microbial diversity, causing bacterial composition variation, especially beneficial bacteria and pathogenic bacteria. These results suggested that nitrite and microplastics stress had adverse effects on the intestinal health of L. vannamei by affecting intestinal tissue morphology, immune response and microbial community.

Preparation and characterization of catalase-loaded solid lipid nanoparticles based on soybean phosphatidylcholine.

BACKGROUND: High-purity soybean phosphatidylcholine (SPC) (94%) were prepared using macroporous resin adsorption chromatography previously. Catalase is a food enzyme for promoting health and protecting against many age-related disease. Solid lipid nanoparticles (SLN) are safe immobilizing systems for efficient protein transportation to biomembranes while avoiding adverse degradation of protein. This study was aimed at developing and characterizing catalase-loaded SLN using SPC as solubilizers and stabilizing agents, to protect catalase from proteolysis. RESULTS: Catalase-loaded SLN were prepared by the double emulsification method and solvent evaporation techniques, using acetone-methylene chloride (1:1, v/v) as an organic solvent, SPC-tripalmitin as oil phase and Poloxamer 188 as a surfactant. The optimized SLN were prepared using an SPC:tripalmitin ratio of 5% (w/w), 20 s plus 30 s sonication, 20 g L⁻¹ Poloxamer 188 and 1:2 (v/v) of oily phase:outer aqueous phase ratio. The mean particle size of SLN was 296.0 ± 7.0 nm, polydispersity index range and zeta potential were 0.322-0.354 and -36.4 ± 0.6, respectively, and encapsulation efficiency reached its maximum of 77.9 ± 1.56%. Catalase, which was found to distribute between the solid lipid and inner aqueous phase, was gradually released from SLN up to 20% within 20 h. Catalase-loaded SLN had stably retained 30% of H2O2-degrading activity for at least 24 h in a proteolytic environment, while free catalase lost its activity within 1 h. CONCLUSION: Catalase can indeed be loaded in tripalmitin-based SLN using SPC as solubilizers and stabilizing agents, which protected it against proteolysis, suggesting the potential application of SPC in delivery and protection of functional food enzyme.

Synergistic poly(lactic acid) photoreforming and H2 generation over ternary NixCo1-xP/reduced graphene oxide/g-C3N4 composite.

Effective utilization of photoexcited electrons and holes is always a challenge in photocatalytic reactions. Herein, we reported ternary NixCo1-xP/reduced graphene oxide/g-C3N4 (NixCo1-xP/rGO/CN) composite as a photocatalyst for synergistic poly(lactic acid) photoreforming and H2 generation in alkaline aqueous solution. The rate of H2 production over the optimal 15Ni0·1Co0·9P/rGO/CN reached 576.7 µmol h-1 g-1, which is 3.6 times as high as binary 15Ni0·1Co0·9P/CN composite. The apparent quantum efficiency of the optimal 15Ni0·1Co0·9P/rGO/CN was 1.7% at λ = 420 nm monochromatic light. Mott-Schottky analysis suggested that the photogenerated electrons transfer along the pathway of CN→rGO→Ni0·1Co0·9P, where rGO and Ni0·1Co0·9P functioned as the medium for electron transporting and reaction site for H2 generation, respectively. Meanwhile, poly(lactic acid) was photoreformed into formate and acetate by the photogenerated holes and hydroxyl radical. This work demonstrates that ternary NixCo1-xP/rGO/CN composite can be applied as a cheap and promising photocatalyst for synergistic plastic photoreforming and H2 generation.

Entropy-Enhanced Mechanochemical Activation for Thermal Degrafting of Surface-Tethered Dry Polystyrene Brushes.

Dry polymer brushes have attracted great attention because of their potential utility in regulating interface properties. However, it is still unknown whether dry polymer brushes will exhibit degrafting behavior as a result of thermal annealing. Herein, a study of the conformational entropy effect on thermal degrafting of dry polystyrene (PS) brushes is presented. For PS brushes with an initial grafting density (σpini) of 0.61 nm-2, degrafting behavior was observed at 393 K, and the equilibrium σp was approximately 0.14 nm-2 at 413 K. However, for brushes with σpini ≤ 0.14 nm-2, thermal degrafting was not observed even if the temperature was increased to 453 K. Furthermore, we found that the degrafting rate was faster for PS brushes with higher σpini and higher molecular weights when σpini > 0.14 nm-2. Our findings confirmed that degrafting is a mechanochemical activation process driven by tension imposed on bonds that anchor the chains to the surface, and the process is amplified by conformational entropy.

[Clinical value of cast post-core porcelain fused to metal crown in restorating residual root and crown of molars].

OBJECTIVE: To investigate the effect of cast post-core porcelain fused to metal crown on the restoration of residual root and crown of molars. METHODS: One hundred and sixty-four residual roots and crowns of molars were treated with root canal therapy and restored by cast core porcelain fused to metal crown. The restoration effect was assessed at the 3rd, 6th, 12th and 24th month. RESULTS: The strength of dental prosthesis retention, marginal fitness, and strength of crowns were satisfactory. The effective rate reached 95.12% during the 2 year follow-up. CONCLUSION: The cast post-core porcelain fused to metal crown is a better method in treating the residual root and crown of molars.