Enhancement of Stent-Induced Thromboembolism by Residual Stenoses: Contribution of Hemodynamics

In vitro stent-induced thromboembolism was altered by the presence of residual stenoses placed upstream or placed upstream and downstream of the stent. Heparinized (3 /ml) bovine blood was gravity fed through a conduit with a deployed coronary stent. Embolism was continuously monitored using a light-scattering microemboli detector, and the thrombus accumulated on the stent at the conclusion of the experiment was assessed gravimetrically. Gaussian stenoses (75% reduction in the cross-sectional area) were placed upstream or upstream and downstream of the stent to alter flow characteristics in the stent region. The presence of stenoses enhanced embolization from the stent in all cases, while end-point thrombus accumulation on the stent decreased with only an upstream stenosis present, and increased when upstream and downstream stenoses were present. Computational fluid dynamics with and without hypothetical model thrombi were used to ascertain the alterations in the flow environment caused by the stenoses and thrombi. Combining the computed hemodynamic parameters with experimental results indicated that increased radial transport of blood components and low wall shear stress provided by the stenoses and thrombi may explain the enhancement of end-point thrombus accumulation. Analysis further showed that thrombi growing at the stenosis-induced reattachment and separation points will be subjected to high shear forces which may explain the increased embolism when stenoses are present. © 2000 Biomedical Engineering Society. PAC00: 8719Uv, 8719Xx, 8780-y     

Kink Bands in High‐Performance Fibers Studied by X‐Ray Microdiffraction

This study reports on the investigation of kink bands within a single high performance fiber. Using microfocus XRD in a scanning acquisition mode, kink bands can be visualized along the length of a fiber in a manner similar to other microscopy techniques. Unlike other techniques, however, µXRD also provides access to internal structural information. For example, from the diffraction data it is possible to reconstruct the complete microgeometry of single kink bands based upon experimental results. This capability opens the door to a range of future studies. This could include tracking the formation and evolution of kink bands in situ, or studying kink bands within fibers embedded within a composite material.

     

人血红细胞在直流电作用后光镊操控的拉曼光谱研究

激光光镊拉曼光谱(LTRS)系统是拉曼光谱和激光光镊的结合,是一种研究细胞的全新方法,可对单个活细胞进行操控和光谱收集。从拉曼光谱特征峰位置、强度和线宽可得到细胞的组成、结构及细胞内物质相互作用的信息。外界因子对细胞的作用可引起细胞的生理变化,这种变化也可以通过拉曼光谱的变化而进行分析。本文是对人血红细胞在不同强度直流电的作用前后拉曼光谱变化的研究,结果表明:人血红细胞在直流电作用前后拉曼光谱有明显的差异,这种变化正是红细胞内信息变化的一种反映。本研究为直流电物理治疗的分子机理提供一定的理论参考。     

Expulsion of Unimers from Polystyrene‐block‐poly(acrylic acid) Micelles

Summary: The pH response of the micelles of polystyrene‐block‐poly(acrylic acid) (PS₂₀₀‐b‐PAA₇₈) in water is studied using a combination of techniques: static light scattering (SLS), dynamic light scattering (DLS), and transmission electron microscopy (TEM). The structure of the micelles in dilute aqueous solution is dependent on pH. At pH values <2.5, the micelles precipitate. At pH values from 2.5 to 3.5, the micelles associate to form micellar clusters. At pH values ranging from 3.5 to 8.0, the micelles are dynamically frozen. At pH > 8.1, some PS₂₀₀‐b‐PAA₇₈ unimers gradually escape from the micelles and subsequently re‐associate to form smaller micelles.

The pH‐responsive behavior of the PS₂₀₀‐b‐PAA₇₈ micelles in solution.     

Homo and Block Copolymers of Poly(β‐benzyl‐L‐aspartate)s and Poly(γ‐benzyl‐L‐glutamate)s of Different Architectures

Homopolypeptides of linear and star‐like architectures were prepared by polymerizing benzylic‐protected L ‐glutamic acid and L ‐aspartic acid N‐carboxyanhydrides (Glu NCA, Asp NCA) in DMF. The polymerization rate of the Glu NCA is faster than that of Asp NCA. Using a simple monoamino initiator, its hydrochloride, di‐, tri‐, and tetraamino functional initiators, homopolypeptides with well‐defined structures and molar masses were obtained. The molar‐mass averages of the poly(γ‐benzyl‐L ‐glutamate)s lie very close to calculated values, according to the initial [M]:[I] ratios, while those of the linear poly(β‐benzyl‐L ‐aspartate)s were lower than the predicted ones. PBAs had somewhat broader molar‐mass distributions than PBGs.

     

Investigation of Nanoparticle Coating by Fluorescence Correlation Spectroscopy

Protecting gene delivery vectors by hydrophilic copolymer coating is a promising approach in targeted gene therapy. Herein we demonstrate the usefulness of FCS in characterizing the coating process of a virus model – latex beads with coumarin‐labeled N‐(2‐hydroxypropyl)methacrylamide copolymer containing thiazolidine‐2‐thione groups. FCS gives an estimation of the average number of polymer chains coating the latex bead, which agrees with light scattering results, giving an evidence of quality of the vector surface modification. FCS is advantageous because it decreases the sample consumption by a factor of 1 000. The coumarin label showed advantages over the previously used fluorescein‐based one.

     

Preservative Induced Polysorbate 80 Micelle Aggregation

Small angle neutron scattering (SANS) studies of a model pharmaceutical formulation reveal how formulation stability depends on the compatibility of individual components. Solutions of two common protein formulation excipients, polysorbate 80 (PS80), a nonionic surfactant that prevents aggregation, and m-cresol, an antimicrobial agent for multi-dose injectable formulations, are investigated. The addition of m-cresol to PS80 solutions leads to solution turbidity and irreversibly alters PS80 micelle morphology. This slow preservative-induced destabilization of PS80 micelles progresses over days or even weeks, which highlights the essential role that aggregation kinetics plays in preservative-surfactant interactions. The temperature-dependence of PS80 micelle growth kinetics is quantified by SANS in the presence of m-cresol. Aggregation is a two-step process, where initial formation of small aggregates is followed by a period of monotonic power-law growth, providing evidence for the mechanism. Total aggregate mass stays constant after initial aggregate formation, and addition of a pH-regulating citrate buffer dramatically accelerates aggregation kinetics.     

振动光谱在药物晶型表征中的应用研究进展

固态药物的多晶型研究对药物质量控制、生产工艺选择、临床疗效评价等发挥重要作用。振动光谱是药物多晶型表征的有力手段之一。本文重点概述了近年来利用傅里叶变换红外(FTIR)光谱技术和拉曼(Raman)光谱技术在活性药物成分(APIs)及药物共晶/盐的多晶型表征中的应用研究进展,阐明两种光谱技术在APIs和药物复合物的晶型分析中的应用特点,为药物开发过程中的结构分析提供理论支持。     

基于氧化石墨烯/金纳米棒的表面增强拉曼散色技术检测循环肿瘤细胞

目的 开发一种结合表面增强拉曼散色（SERS）光谱与静电吸附的方法用于检测循环肿瘤细胞。方法 氧化石墨烯经过聚苯乙烯磺酸钠（PSS）的非共价修饰后,通过金种子法原位合成氧化石墨烯/金纳米棒（GO/GNR）复合材料,再利用聚-二烯丙基二甲基氯化铵（PDDAC）非共价修饰GO/GNR,使其表面带正电荷。通过电荷靶向作用实现GO/GNR与肿瘤细胞的靶向结合,用SERS技术对GO/GNR-肿瘤细胞复合物进行检测。采集健康志愿者血液标本,将不同密度的肿瘤细胞加入血液标本中制成模拟血样,按上述方法检测模拟血样中的肿瘤细胞。结果 带正电荷的GO/GNR复合材料能够有效地与肿瘤细胞靶向结合,并且能够在50~10 000个细胞的范围内对肿瘤细胞进行拉曼光谱检测,但白细胞对肿瘤细胞的检测有一定的干扰。结论 GO/GNR复合材料可作为SERS探针实现对循环肿瘤细胞的拉曼光谱检测。     

基于XRD,NIR及拉曼光谱技术快速鉴别白矾、枯矾真伪

目的:分析白矾、枯矾及其伪品的X射线衍射(X-ray diffraction,XRD),拉曼和近红外(Near Infrared,NIR)光谱特征与差异,建立快速鉴别白矾、枯矾和常见伪品的新方法。方法:从不同药材市场购得白矾9批,枯矾5批,自制枯矾2批。采集以上样品的XRD,NIR和拉曼光谱,归纳其光谱特征,分析光谱明显差异。结果:明矾和其伪品铵明矾的XRD,NIR及拉曼光谱具有明显差异。在XRD图谱中,铵明矾在2θ=14.56°处有1小峰,正品白矾没有此峰;在NIR光谱中,铵明矾在4 650 cm~(-1)处有1特征峰,而正品白矾无此峰;在拉曼光谱中,正品白矾在990 cm~(-1)处的最强峰发生分裂,974 cm~(-1)处产生1中等强度尖峰,而铵明矾无974 cm~(-1)峰,以上差异可用于二者快速鉴别。此外,正品枯矾XRD图谱具有9个明显特征峰(2θ=11.18°,21.88°,24.58°,31.42°,33.76°,38.25°,39.94°,50.24°,50.99°),NIR光谱在7 000 cm~(-1)和5 150 cm~(-1)处有2个较为平缓的吸收峰,可作为鉴别枯矾真伪的特征峰。结论:XRD,NIR和拉曼光谱特征可共同用于白矾、枯矾及其伪品的准确鉴别;NIR结合拉曼光谱技术能够为白矾及其炮制品的质控和快检提供快速准确的新方法。