Controllable biodegradability, drug release behavior and hemocompatibility of PTX-eluting magnesium stents

Cardiovascular magnesium-based stents have been already applied in patients. However, their high corrosion rate hinders their clinical application. In this study, we adopt a new approach in the design of a Mg-based stent to improve the biodegradation rate and the drug release rate. By fabricating a micro-arc oxidation/poly-l-lactic acid (MAO/PLLA) composite coating on the magnesium alloy AZ81 substrate, the corrosion resistance decreased and the biodegradation rate became controllable. The drug release coating was composed of one Poly(dl-lactide-co-glycolide)/paclitaxel (PLGA/PTX) layer and one pure PLGA blank layer without paclitaxel, and this coating also functions to provide controlled biodegradation rate of the stent. The drug release rate was controlled by controlling the ratio of the LA:GA of the PLGA without PTX. The scanning electron microscopy (SEM) images were used to demonstrate the morphology of the samples before and after this modification. The blood compatibility of the samples was demonstrated by the platelet adhesion test. The drug release was determined by ultraviolet-visible (UV-visible) spectrophotometer. The result showed that the PLLA effectively sealed the micro-cracks and micro-holes on the surface of the MAO coating to give controllable biodegradation of the AZ81. The drug release rate of PTX exhibited a nearly linear sustained-release profile with no significant burst releases that would come from the uncontrolled oxidation/corrosion of AZ81. The samples modified had better hemocompatibility than 316L stainless steel.     

Probabilities of hitting a convex hull

In this note, we consider the non-negative least-square method with a random matrix. This problem has connections with the probability that the origin is not in the convex hull of many random points. As related problems, suitable estimates are obtained as well on the probability that a small ball does not hit the convex hull.     

Reversible Thermochromism and Strong Ferromagnetism in Two‐Dimensional Hybrid Perovskites

Two‐dimensional (2D) hybrid perovskites have shown many attractive properties associated with their soft lattices and multiple quantum well structure. Herein, we report the synthesis and characterization of two new multifunctional 2D hybrid perovskites, (PED)CuCl₄ and (BED)₂CuCl₆, which show reversible thermochromic behavior, dramatic temperature‐dependent conductivity change, and strong ferromagnetism. Upon temperature change, the (PED)CuCl₄ and (BED)₂CuCl₆ crystals exhibit a reversible color change between yellow and red‐brown. The associated structural changes were monitored by in situ temperature‐dependent powder X‐ray diffraction (PXRD). The (BED)₂CuCl₆ exhibits superior thermal stability, with a thermochromic working temperature up to 443 K. The conductivity of (BED)₂CuCl₆ changes over six orders of magnitude upon temperature change. The 2D perovskites exhibit ferromagnetic properties with Curie temperatures around 13 K.     

Cu掺杂对介孔VOx-TiO2催化苯羟基化制苯酚的影响

将Cu作为第二金属,制备了不同Cu掺杂量的和不同温度下焙烧的双金属改性的Cu/VOx-TiO2复合催化剂,并用于液相苯直接羟基化制苯酚反应中.固定钒的含量为4.3%,合成了一系列不同Cu掺杂量(w=0.29%~2.5%)的催化剂,并在不同的温度下(350~650°C)进行了焙烧.利用X射线衍射、N2吸附-脱附、扫描电镜、透射电镜、H2程序升温还原以及X射线光电子能谱对催化剂进行了表征.结果表明,加入Cu后催化剂仍保持有序的介孔结构,并且有效地促进了VOx物种在载体TiO2上的分散和VOx物种的还原,同时提高了催化剂的热稳定性,其中Cu以+2价的形态存在于催化剂中.另外,考察了催化剂用量,反应温度等对苯羟基化反应性能的影响.     

Synthesis of Di‐ and Trixanthones that Display High Stability and a Visual Fluorescence Response to Strong Acid

Three dixanthones ( 1 – 3 ) and an unprecedented C_3h‐symmetric trixanthone ( 4 ) were synthesized through a three‐step approach in overall yields above 63 %. These compounds possessed a planar π‐conjugated system and formed tight face‐to‐face columnar stacks, as confirmed by single‐crystal structural analysis. In comparison with xanthone, the fluorescence emissions of compounds 1 – 4 showed significant red‐shifts, with improved quantum yields. Moreover, the fluorescence emissions of compounds 1 – 4 could be modulated in a strongly acidic environment without decomposition, which led to a further red‐shift of the emissions, as well as enhancement of the emission intensities. These compounds have potential applications as optoelectronic materials and/or chemosensors.     

Designed synthesis and chiroptical properties of regioregular poly(p-phenyleneethynylene-alter-m-phenyleneethynylene) bearing (−)-trans-myrtanoxyl side groups

Two regioregular poly(p-phenyleneethynylene-alter-m-phenyleneethynylene)s bearing (−)-trans-myrtanoxyl side groups with different substitution patterns were designed and synthesized, e.g. Myr-PMPE-1 and Myr-PMPE-2. In Myr-PMPE-1, the side chiral groups are distributed uniformly along the backbone. In Myr-PMPE-2, the distribution of the side chiral groups is alternatively crowded and loose. Both of these two polymers show no CD signal in solutions because of their good solubility. The investigations of chiroptical properties of these two polymers were carried out in the form of spin-coated films. The films were annealed above the glass temperature of the corresponding polymer, and the effects of annealing temperature and time on the properties of the films were investigated by UV-Vis absorption, fluorescence and circular dichroism spectra. The results show that annealing treatment had no significant effect on the properties of Myr-PMPE-1, including UV-Vis absorption, fluorescence and optical activity. The maximum absolute value of dissymmetry factor (|g _max|) was 1.62 × 10⁻⁴. On the other hand, annealing treatment significantly affected the properties of Myr-PMPE-2. Without annealing or being annealed below 100°C, Myr-PMPE-2 films show almost no Cotton effect. In contrast, when annealed above 120°C, the absorption and emission of Myr-PMPE-2 films slightly red shifted with increasing annealing temperature and annealing time. Most importantly, the intensity of CD signals increased significantly and the optical activity of Myr-PMPE-2 films markedly increased. After annealing at 140°C for 4 h, the |g _max| of Myr-PMPE-2 films was increased up to 3.07 × 10⁻³, about one order of magnitude higher than that of Myr-PMPE-1 films. __________ Translated from Acta Polymeric Sinica, 2008, 3 (in Chinese)     

Synthesis and chiroptical properties of poly (p‐phenylenevinylene‐alt‐m‐phenylenevinylene) bearing (−)‐trans‐myrtanoxyl groups on the p‐phenylene rings

Chiral poly(p‐phenylenevinylene‐alt‐m‐phenylenevinylene)s bearing (?)‐trans‐myrtanoxyl groups on the p‐phenylene rings were synthesized by Wittig's reaction and Heck's reaction, respectively, namely Myr‐PMPV‐w and Myr‐PMPV‐h correspondingly. The chiroptical properties of the polymers were investigated in chlorobenzene solution by circular dichroism. The results showed that both Myr‐PMPV‐w and Myr‐PMPV‐h showed no Cotton effect due to their irregular molecular structure. By the treatment with I₂, most of the cis‐vinylene linkages in Myr‐PMPV‐w were converted to trans‐vinylenes, consequently, the structure of Myr‐PMPV‐w became much more regular, and the resulting polymer ( iso‐Myr‐PMPV‐w ) showed strong bisignate Cotton effects in the π–π* transition. Compared to its analogous poly(p‐phenylenevinylene) (PPV) ( iso‐Myr‐PPV‐w ), iso‐Myr‐PMPV‐w showed much stronger Cotton effect, its maximum g value was about one order of magnitude higher than that of iso‐Myr‐PPV‐w under the same conditions. With increasing concentration and decreasing temperature, the g_max value of iso‐Myr‐PMPV‐w increased, and the maximum absorption was slightly blue‐shifted, but the shape and range of absorption curves did not changed significantly, and no clear isosbestic point could be observed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3336–3343, 2008