Ruthenium-containing supramolecular nanoparticles based on bipyridine-modified cyclodextrin and adamantyl PEI with DNA condensation properties.

Exploring safe and highly efficient gene carriers made from biocompatible constituents has great prospects for clinical gene therapy. Here, a supramolecular gene delivery system was readily constructed by assembling adamantyl-modified polyethylenimine (PEI-Ada) units with a versatile ruthenium bipyridine-modified cyclodextrin (Ru-CD) through host-guest interactions. The photophysical and morphological features of the PEI-Ada@Ru-CD nanoparticles were systematically characterized by techniques including UV-vis absorption spectroscopy, fluorescence spectroscopy, transmission electron microscopy, dynamic light scattering, and zeta potential experiments. The small size and suitably positive zeta potential of the nanoparticles facilitated their cellular uptake and gene transfection. As expected, DNA interaction studies, which were performed using agarose gel electrophoresis and atomic force microscopy, showed that the ability of the nanoparticles to condense DNA was higher than that of the gold standard, i.e., PEI, at low N/P ratios. The design of these ruthenium-containing supramolecular nanoparticles based on bipyridine-modified cyclodextrin and adamantyl PEI has great prospects in the development of gene delivery vehicles.

[Spatiotemporal pattern of alpine grassland productivity in Qiangtang Plateau].

Based on the meteorological data and remote sensing data, and by using vegetation-climate comprehensive model and CASA model, this paper analyzed the climate change trend and the spatiotemporal pattern of alpine grassland potential and actual net primary productivity (NPP) in Qiantang Plateau. In 1955-2004, the mean annual temperature and annual cumulated precipitation in the Plateau increased by 1.37 degrees C and 63 mm, respectively. The climate in the central and eastern parts of the Plateau became warmer and wetter, whereas it was warmer and dryer in the western part. However, the regional climate change did not yet result in grassland degradation. The mean potential NPP of alpine grassland was in the order of eastern part > central part > western part. From 1982 to 2004, the potential NPP in the central part had the largest increment (0.55 t x hm(-2) x a(-1)), followed by in the eastern part (0.51 t x hm(-2) x a(-1)) and western part (0.21 t x hm(-2) x a(-1)), which was consequent with the spatiotemporal pattern of climate change in the study area. In contrast, the actual NPP in the eastern, central, and western parts in the past two decades was -0.19, -0.03, and 0.20 t x hm(-2) x a(-1), respectively. Overgrazing was the main reason of grassland degradation in the central and eastern parts, and the central part was the key layout area for the implement of 'grazing withdrawal and management of grassland' project.

Porous anodic alumina with continuously manipulated pore/cell size.

We used polyethyleneglycol (PEG) as a modulator to manipulate pore and cell sizes in the porous anodic alumina (PAA) fabrication. It is shown for the first time that continuous manipulation of the pore size of PAA can be realized. Combined with the coexistent cell-size controlling effect, the morphology and properties of this important nanoscale template and separation membrane can be precisely regulated. The pore size modulation mechanism is proposed on the basis of the morphological and electrochemical results. The presence of PEG in the electrolyte results in a more compacted structure of the barrier layer alumina (BLA), although the barrier layer thickness does not change considerably. In addition, the additive can obviously restrain the chemical dissolution of alumina and shape smaller pores. These two effects combined with the increased viscosity of the electrolyte slow down the ion transportation and diminish the anodization current. Thus, the burning-down phenomena of the aluminum substrates can be avoided at relatively high voltage anodization, and an interpore distance up to 610 nm can be achieved.