Functionalized DNA Nanostructures for Nanomedicine

DNA nanotechnology utilizes synthetic DNA strands as the building material to construct nanoscale devices, and the field has developed rapidly over the past decade. Recently, the use of DNA nanostructures for various applications, particularly biomedical ones, has drawn great interest. This review focuses on the most recent research directed at utilizing functionalized DNA devices for nanomedical applications and presents representative research progress in disease diagnosis, treatment and prevention. In addition, the safety and future clinical applications of DNA nanostructures are discussed.     

Preparation and characterization of star-shaped nylon 6 with high flowability

Three kinds of star-shaped nylon 6 samples with different branched-chain length were prepared by the hydrolytic polymerization of ε-caprolactam using trimesinic acid as trifunctional reactant. The structure of prepared star-shaped nylons was characterized by infrared spectroscopy and ¹H-NMR. Compared with linear-chain nylon 6, star-shaped nylons with the equivalent molecular weight present higher melt flow indices and lower relative viscosities due to decreased molecular dimensions and reduced hydrogen bond interactions between neighboring molecules. The molecular weights of the products were determined by end-group titration and ¹H-NMR, and the molecular weight distributions (MWDs) were evaluated by gel permeation chromatography. The results show that the molecular weight decreased and the MWD narrowed as the concentration of trimesinic acid increased. Wide-angle X-ray diffraction patterns of star-shaped and linear-chain nylons show that increasing the concentration of trimesinic acid leads to good symmetry and high crystallizability, but this also degrades crystal perfection as observed using a polarized optical microscope. The viscosity of nylon 6 can be significantly reduced while maintaining its mechanical performance through the use of star-branching and an appropriate concentration of trimesinic acid.     

Monophosphorylation of cornstarch to improve its sizing properties for heat‐sensitive wool yarns at reduced temperature

Commercial cornstarch was mono‐phosphorylated to different levels of substitution in order to investigate the effect of phosphorylation on the properties of cornstarch for sizing heat‐sensitive wool yarns at reduced temperature. The influences of starch phosphorylation and sizing temperature upon apparent viscosity and viscosity stability of cooked starch paste, starch retrogradation, adhesion to wool fibers, performance of starch film, aerobic biodegradation, mechanical properties, and hairiness of sized wool yarns were evaluated. The phosphorylation level was varied from 0.021 to 0.082 in degree of substitution (DS), while the temperature considered was from 60 to 95°C. It was found that mono‐phosphorylation of starch resulted in enhanced paste stability, reduced retrogradation, strong adhesion to wool fibers, increased performances of starch film, improved mechanical properties of sized wool yarns, and decreased hairiness on surface of sized yarns even if paste temperature was lowered to 60°C. Initially increasing phosphorylation level enhanced positive effects, but excessively increasing the level was not applicable due to marked reduction in tensile strength of starch film. The phosphorylation with a DS value of 0.061 could improve the performances of cornstarch for sizing wool yarns at 60–80°C. Moreover, measurement on BOD₅/COD ratios demonstrated that the phosphorylation did not impede aerobic biodegradation of starch. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Methylation of methyltrichlorosilane with methyl chloride over active metals and activated carbon

Gas phase methylation of methyltrichlorosilane with methyl chloride to high-valued dimethyldichlorosilane was carried out by using metallic aluminum as a chlorine acceptor in the co-presence of activated carbon, tin, and zinc. The addition of activated carbon in metallic aluminum significantly enhanced the methylation of methyltrichlorosilane, and dimethyldichlorosilane was dominantly produced. Activated carbon played a catalyst role in the methylation reaction. When active metals, such as tin and zinc, were added in the mixture of aluminum and activated carbon, the active metals and activated carbon synergistically catalyzed the methylation of methyltrichlorosilane with methyl chloride toward the formation of dimethyldichlorosilane.     

Recent Advances in Solution-Processed White Organic Light-Emitting Materials and Devices

Solution-processed white organic light-emitting diodes (WOLEDs) have drawn great attention both in the academic and industrial research communities due to the potential application in low-cost, large-area, solid-state lightings. Issues related to the device efficiencies are largely hampering progress in this field. Alongside the development of new materials and novel device architectures, distinct progress has been made for such white devices. In particular, the all-phosphorescent light-emitting strategy has been intensively developed in recent years, mainly focusing on a host guest, doping-system-based, single-active-layer structure and a solution-processed, multilayer device structure. Novel approaches, including white single polymers and excimer-/exciplex-based white devices, have also appeared as a promising choice and received great attention. As a prerequisite, the issue of the morphology of the emissive layer is also important and has an influence on the optoelectronic behavior of the device. Herein, major advances in solution-processed WOLEDs based on polymers, dendrimers, or solution-processed small molecules are summarized. Special attention is focused on the main progress in high-efficiency, solution-processed WOLEDs with the key strategies mentioned above and the morphology issue in these systems. The remaining challenges in pursuing the development of reliable and energy-saving lighting devices are also discussed.