表面巯基化修饰的磁性Fe_3O_4纳米粒子合成与表征

通过化学共沉淀法制备了粒径约30nm的磁性四氧化三铁(Fe3O4)纳米粒子,并采用3-巯丙基三乙氧基硅烷(MPTES)将Fe3O4纳米粒子表面修饰上巯基(-SH)官能团,获得了表面巯基化的磁性Fe3O4纳米粒子。利用X-射线粉末衍射仪(XRD),透射电子显微镜(TEM),带有能谱仪(EDS)的扫描电子显微镜(SEM),光电子能谱仪(XPS),以及磁学测量系统(MPMS)对粒子的结构和性能进行了表征和分析。结果表明:表面巯基化后的磁性粒子粒径略有增加,室温下磁化强度由原来的64emu/g变为62emu/g,较好地保留了原始磁性特征。研究结果对巯基化磁性纳米粒子实现生物分子结合、固定负载乃至生物传感的应用具有重要意义。     

精氨酸修饰的磁性纳米基因载体的研究

采用多层修饰方法制备出精氨酸修饰的磁性纳米基因载体,对样品进行了粒度分析、Zeta电位分析、耐酸性能、生物相容性、体外细胞转染性能研究。结果显示,精氨酸修饰的磁性纳米颗粒均匀,分散性好,大多呈圆球型,平均粒径为15 nm,粒径范围10~20 nm,其Zeta电位为+29.3 mV;多层修饰的纳米磁粒在pH 2.0的酸中具有很好的耐酸性能,而未处理的纳米粒子在酸溶液中发生了溶解。MTT实验结果显示,纳米颗粒与细胞有良好的生物相容性;体外细胞转染的结果表明,精氨酸修饰的纳米磁粒能介导pEGFP-N1质粒转染HepG2细胞,并在细胞中表达绿色荧光蛋白。因此,精氨酸修饰的磁性纳米颗粒作为一种新型非病毒基因载体具有介导核酸类生物大分子的应用价值。     

Fe_3O_4磁性纳米粒子及其生物医学应用研究进展

Fe_3O_4磁性纳米粒子因具有生物相容性、比表面积大、低毒性和高饱和磁化强度等优点,使其被广泛应用于生物医学领域。本文简单介绍了Fe_3O_4磁性纳米粒子的制备方法,包括共沉淀法、微乳液法、热分解法、水热法、溶胶-凝胶法、生物合成法等,并对共沉淀法、热分解法和水浴法3种常用制备方法的优缺点进行了比较;重点阐述了Fe_3O_4磁性纳米粒子的表面修饰,包括有机小分子修饰、有机高分子修饰和无机纳米材料修饰;重点论述了Fe_3O_4磁性纳米粒子在生物医学领域的应用研究,主要包括核磁共振成像、药物递送体系、蛋白质和核酸分离、血液净化以及肿瘤热疗等,充分显示了Fe_3O_4磁性纳米粒子在生物医学领域的应用价值;最后指出Fe_3O_4磁性纳米粒子今后的主要发展方向和亟待解决的问题。     

氨基化Fe_3O_4纳米粒子的制备及对胃癌细胞的毒性评价

采用共沉淀法制备了四氧化三铁纳米粒子(Fe_3O_4),并在Fe_3O_4纳米粒子表面修饰上了氨基。透射电子显微镜(TEM)和傅里叶变换红外光谱(FTIR)显示,纳米粒子分散性良好,粒径约为10 nm,氨基成功修饰在了纳米粒子的表面。以胃癌SGC-7901为目的细胞,依据RGR值考察了Fe_3O_4-NH_2纳米粒子的细胞毒性等级,结果显示,在一定浓度范围内,细胞死亡率与Fe_3O_4-NH_2纳米粒子的浓度成正相关,低于51.2μg/m L时,Fe_3O_4-NH_2纳米粒子的细胞毒性相对较小,Fe_3O_4-NH_2纳米颗粒具有较好的生物相容性。     

Fe_3O_4的制备及表面修饰

Fe_3O_4磁性纳米粒子由于其具有较高的磁性、良好的生物相容性、较低的毒性及简单的制备条件等优点,成为应用最为广泛的一种磁性纳米材料。文章主要介绍了Fe_3O_4磁性纳米粒子的主要合成方法,及利用无机材料、有机小分子材料和高分子材料对Fe_3O_4磁性纳米粒子的修饰方法。     

疏水修饰磁性壳聚糖载药纳米粒子的制备与表征

利用O-羧甲基壳聚糖(O-CMC)的表面多种官能团(如-NH_2,-OH,-COOH等)与胆酸(CA)进行化学修饰得到两亲性共聚物,再以反溶剂法将Fe_3O_4和阿霉素(DOX)包埋在两亲性共聚物疏水的核中,制备两亲性的磁性壳聚糖载药纳米粒子,并对磁性载药纳米粒子的形貌、粒径大小、磁性、药物控释等进行了研究。结果表明:磁性壳聚糖纳米粒子有较高的药物包埋效率(92.3%),与自由阿霉素相比,磁性复合物具有明显的缓释作用和pH响应性;同时,有较好的超顺磁性。这些说明制备的疏水修饰磁性壳聚糖载药纳米粒子具有双重响应性,有望作为药物输送载体对肿瘤进行实时跟踪、诊断和治疗。     

交联羧甲基-β-环糊精聚合物修饰的Fe3O4磁性纳米粒子对盐酸阿霉素的负载和释放研究

采用共沉淀法制备了交联羧甲基-β-环糊精聚合物修饰的Fe₃O₄磁性纳米粒子(MNPs@CDP),将其作为药物载体负载抗癌药物盐酸阿霉素(DOX),通过MTT实验来评估MNPs@CDP的生物相容性和吸附DOX后复合物(MNPs@CDP/DOX)的细胞毒性，并通过荧光成像技术观察了MNPs@CDP/DOX中DOX在HepG2肝癌细胞中的释放情况。结果表明MNPs@CDP在小于30 mg/mL的浓度范围内表现出了较好的生物相容性，并且MNPs@CDP/DOX和HepG2细胞共培养4 h后能够在细胞中释放大量药物，并能够有效杀死癌细胞。     

叶酸受体介导的CdS纳米颗粒的生物成像

以巯基乙酸为修饰剂,合成了具有特殊光学性质的水溶性硫化镉( CdS)纳米颗粒.通过红外吸收光谱、荧光光谱和透射电子显微镜对产物的光学性能和晶体结构进行了表征,结果表明经巯基乙酸改性、聚乙烯亚胺及叶酸修饰的CdS纳米颗粒为球形,粒径约180 nm左右,并且有较高产率,同时具有良好的分散性、稳定性及生物相容性;利用激光扫描...     

超声波化学共沉淀法制备SiO_2/Fe_3O_4复合粒子

为了防止纳米级Fe3O4的氧化及团聚,在其表面包覆一层二氧化硅,本文设计了Si O2/Fe3O4复合粒子的制备工艺。本论文采用的制备方法是超声波化学共沉淀法,用X-射线衍射仪(XRD)、扫描电镜(SEM)、傅里叶红外转换光谱(FTIR)、低温氮吸附比表面积测试仪等研究了粒子晶相、组织形貌及化学键。结果表明,Si O2/Fe3O4复合粒子形貌为球形,表面具有孔隙,颗粒平均尺寸约250 nm。Si O2/Fe3O4复合粒子不仅具有良好的化学稳定性和生物相容性,而且为下一步表面修饰打下坚实的基础。     

核壳结构磁性纳米复合物的合成及载药性能

利用化学交联法合成了壳聚糖改性的四氧化三铁磁性纳米复合物。通过透射电子显微镜(TEM)、傅里叶转换红外光谱(FTIR)、粒度分析仪(Nano-ZS)和振动样品磁强计(VSM)对该复合物的形貌、粒径、物相组成及磁性能进行了表征分析。表明该磁性纳米复合物具有核壳结构。再用超声法合成了阿霉素-壳聚糖修饰的磁性纳米包合物,用紫外-可见(UV-Vis)分光光度计检测了该复合物的包封率,平均值达到46.13%。通过四唑盐(MTT)比色法证明了包合物对K150细胞的生物抑制作用。以上结果表明,该磁性纳米复合物具有良好的生物相容性和载药活性。     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Novel polyurethane coating technology through glycidyl carbamate chemistry

Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.