铁质纳米粉体对甲基乙烯基硅橡胶力学性能的影响

目的探讨铁质纳米粉体改性甲基乙烯基硅橡胶的力学性能变化及其在基胶中的分散状态。方法根据国家标准对前期制备出的纳米铁粉增强硅橡胶和碳包铁粉增强硅橡胶复合材料进行邵氏A硬度、拉伸强度、扯断伸长率、扯断永久变形率、撕裂强度等力学性能指标测试,使用热场发射扫描电镜（TFE．SEM）观察复合材料的表面形貌和断口形貌,了解纳米铁在硅橡胶基体的分散状态。结果复合材料试件的邵氏A硬度、拉伸强度、扯断伸长率、扯断永久变形率、撕裂强度的均值随着铁质纳米粉体添加量的增加而增加。当纳米铁在配方中的份数大于17份、碳包铁的份数大于19份时,复合材料的拉伸强度均值不再增加反而呈下降趋势;当铁质纳米粉体的在配方中超过15份时,扯断伸长率、撕裂强度的均值开始下降。铁质纳米微粒在硅橡胶的表面分散均匀,在配方比为85：15的硅橡胶,纳米铁试样的断面及配方比87：13的硅橡胶／碳包铁试件的断面,可观察到粉体的团聚体。结论纳米铁粉体和碳包铁粉体对甲基乙烯基硅橡胶力学性能的补强作用主要取决于纳米粉体的粒径、添加量以及在基胶中的团聚程度。     

空气介质阻挡辉光放电增强硅橡胶/铁质纳米复合材料的表面亲水性

背景：医用硅橡胶的固有缺点是X射线显影性能欠佳和表面疏水性。添加显影标记物铁质纳米微粒可赋予硅橡胶X射线影像可视性的功能,铁质纳米微粒本体改性硅橡胶表面湿润性的变化尚不清楚,设想表面处理以提高硅橡胶/铁质纳米微粒复合材料的亲水性。 目的：观察硅橡胶/铁质纳米微粒复合材料表面湿润性、亲水改性及表征。 方法：使用空气介质阻挡辉光放电分别对前期制备出的配方比为95∶5,90∶10,85∶15的硅橡胶/纳米铁(INESR)和硅橡胶/碳包铁(Fe/CESR)复合材料表面进行改性,对照组为甲基乙烯基硅橡胶(MVSR)。 结果与结论：INESR和Fe/CESR与MVSR相比,表面水接触角减小幅度不大,疏水性未获得明显改善。经空气介质阻挡辉光放电对硅橡胶/铁质纳米微粒复合材料处理后,表面的亲水性得到较大提高,不同配方比INESR和Fe/CESR的水接触角均降低(P < 0.05);扫描电镜显示改性使试件表面受到刻蚀,粗糙度增加,但无空洞或裂隙;X射线光电子能谱分析表明材料表面的化学成分均发生变化,含氧基团大幅增加,含碳基团则明显减少,含硅基团小幅增加,出现含氮基团,说明改性使氮元素被结合到试件的表面,空气介质阻挡辉光放电处理硅橡胶/铁质纳米微粒复合材料的表面可实现亲水改性。     

铁质纳米粉体对甲基乙烯基硅橡胶表面性质的影响*

背景：铁质纳米粉体填入甲基乙烯基硅橡胶可构建出X射线平片可视的新型复合材料,但复合材料的表面性质尚不清楚。 目的：探讨铁质纳米粉体对甲基乙烯基硅橡胶表面性质的影响。 方法：将前期制备出的纳米铁粉增强硅橡胶和碳包铁粉增强硅橡胶复合材料作为实验组,甲基乙烯基硅橡胶为对照组比较观察。 结果与结论：与对照组的表面性质相比,实验组材料的表面变化包括表面粗糙度的Ra值和Ry值升高,纳米铁粉升高Ry值的效果更为明显;基胶分子链之间的纳米颗粒增多;表面C、O、Si等元素的原子百分比发生变化,碳包铁粉升高表面含碳基团的幅度较大;添加纳米铁粉的表面水接触角小幅减小,表面能却降低;添加碳包铁粉的表面水接触角小幅升高,表面能增加;表面自由能的极性分量增加。说明纳米铁或碳包铁均导致甲基乙烯基硅橡胶表面性质的改变,但变化的结果不全相似,这与纳米铁和碳包铁的结构、化学组成不同有关。     

医用硅橡胶的生物相容性缺点及现代改良

硅橡胶具有性能稳定、易于塑形、产品效益可观的优点,已广泛应用于生物医学工程领域和医疗卫生行业.尽管如此,硅橡胶在生物医学领域中的应用仍然受到其自身缺陷的挑战.表面疏水性、自身影像相容性欠佳、长期植入体内后发生钙化乃是医用硅橡胶制品在生物相容性方面亟待克服的缺点.近几年来国内外专家针对以上缺点进行了诸多改良研究,热点主要集中于硅橡胶的表面湿润性增加、X-线阻射功能增强、防钙化预处理等方面.取得了阶段性成果,但尚未使医用硅橡胶的生物相容性达到理想的境界.     

无机纳米填料对植入硅橡胶生物相容性的影响北大核心

背景:硅橡胶是人体组织、器官外科修复重建的常用生物材料,但其自身存在生物相容性缺陷,无机纳米填料为植入硅橡胶的生物相容性改良和构建具有特定功能的复合材料提供了新契机。目的:综述植入硅橡胶添加无机纳米填料改性在生物相容改良研究方面已取得的成果及不足。方法:在PubMed、Web of Science和Medline等英文生物医学数据库,输入“siloxane,silicone rubber,inorganic nano-filler,metal nano-filler,metal oxide nano-filler,carbon nanoparticles”关键词,在万方、CNKI和维普等中文数据库输入“硅橡胶、无机纳米填料、纳米金属、纳米金属氧化物、纳米碳”关键词,分别检索出与无机纳米填料改性硅橡胶的相关文献,时间跨度从2014年1月至2020年10月。结果与结论:利用纳米金属及其氧化物和纳米新碳填料对植入硅橡胶本体或表面进行改性,增进了硅橡胶的生物相容性,可在细胞生长、抗凝血、表面特性、力学性能、耐久性、抗感染功能化等方面产生积极影响。未来需研究不同纳米填料对硅橡胶表面性质(如拓扑结构、电荷、湿润性)造成的细胞增殖移行机制、纳米金属杀菌剂在硅橡胶表面控释阳离子的细菌-纳米粒子相互作用调节策略,以及植入后潜在的纳米毒性。     

长循环超顺磁性氧化铁脂质体纳米微粒的制备及理化性质**☆

背景：常见的超顺磁性氧化铁纳米微粒都局限应用于网状内皮系统病变的诊断。 目的：尝试制备新型MR对比剂长循环超顺磁性氧化铁纳米微粒脂质体纳米微粒,并对其理化性质进行测定。 方法：采用以下方法制备长循环超顺磁性氧化铁脂质体纳米微粒：①精密称取一定量DSPG、DSPE-PEG2000,采用薄膜分散法合成长循环空白脂质体纳米微粒。②采用化学共沉淀法,在碱性条件下与月桂酸反应形成月桂酸稳定的超顺磁性氧化铁纳米微粒。③将上述反应产物以一定比例混合,加入TES缓冲液透析3 d,过凝胶柱去除过大的脂质体及游离的磷脂。 结果与结论：长循环超顺磁性氧化铁脂质体在电镜下显示为类圆形、大小较均匀。衍射图说明产物均为面心立方尖晶石结构的Fe3O4,而且粒子的结晶状态很好。多分散系数为0.212。长循环超顺磁性氧化铁脂质体纳米微粒铁含量为6.721 3 g/L。长循环超顺磁性氧化铁脂质体T2值随着铁浓度的增加逐渐下降。提示制备的长循环超顺磁性氧化铁脂质体纳米微粒粒径大小适宜,分布均匀,可制成适合于皮下或静脉注射的制剂。     

纳米微粒介导Bcl-xl小干扰RNA诱导人肺腺癌细胞凋亡

目的 探讨纳米微粒介导的Bcl-xl小干扰RNA(siRNA)对人肺腺癌A549细胞凋亡的影响.方法 制备包载Bcl-xl siRNh的纳米微粒,体外培养人肺腺癌A549细胞.以纳米微粒介导将人工合成的Bcl-xl siRNA转染细胞后,将细胞分为4组:生理盐水组、纳米微粒组、siRNA-c-纳米微粒组及siRNA-纳米微粒组,其中siRNA-c-纳米微粒组及siRNA-纳米微粒组又分为0.1、0.2、0.4、0.8 μmol/L4个浓度组.应用TUNEL法检测肺癌细胞凋亡;RT-PCR半定量检测Bcl-xl mRNA的表达;免疫细胞化学染色法检测Bcl-xl蛋白的表达.结果 转染Bcl-xl siRNA后,各处理浓度组的肺腺癌细胞凋亡指数随浓度的增加而逐渐升高[0.1、0.2、0.4、0.8 μmol/L组分别为(19.7±2.6)%、(32.4±5.5)%、(46.0±5.3)%和(55.4±5.9)%],与生理盐水组、纳米微粒组及同浓度的siRNA-c-纳米微粒组相比,差异均有统计学意义(P均<0.05).转染浓度为0.8 μmol/L时,肺腺癌细胞内Bcl-xl mRNA及其蛋白的表达明显降低(P<0.05),Bcl-xl蛋白表达阳性单位下降至0.0787±0.0233;Bcl-xl mRNA表达下降至0.856±0.242,与其它各组差异有统计学意义(P<0.05).结论 纳米微粒能有效介导Bcl-xl siRNA进入肺腺癌细胞.Bcl-xl siRNA能够特异性减少肺腺癌细胞的Bcl-xl的mRNA和蛋白的表达,抑制肿瘤细胞增殖及诱导细胞凋亡.     

膀胱癌图像引导放疗中基于软组织灰度值与基于内植标记物的锥形束CT校准比较

目的:锥形束CT的X线容积成像系统(XVI)可执行多种方式校准。本研究目的是评价基于软组织灰度值与同基于膀胱内植标记物的校准方法准确性之间的差异。方法:所有病人接受锥形束CT图像引导下的常规图像引导放疗。将病人分为基于软组织灰度值自动校准试验组和基于膀胱内植标记物手动校准参考组,在确认标记物准确性后,比较了两种方法在3D空间向量和左右(LR)、头脚(SI)、前后(AP)3个方向上的差异。结果:两种方法的3D空间向量差异平均值为0.65 cm;左右方向(LR),头脚方向(SI),前后方向(AP)差异平均值分别为0.03、0.45和1.67 cm。结论:膀胱癌图像引导放疗中基于软组织灰度值的自动校准方法在准确度上劣于基于膀胱内植标记物的手动校准。避免标记物植入和新的图像计算、分析方法是未来发展趋势。     

两种偶联剂改性纳米二氧化硅可影响树脂基托的力学性能

背景：聚甲基丙烯酸甲酯基托材料因其良好的生物相容性,色泽好,易于加工成型等优点被广泛使用,但因其韧性、硬度问题也存在容易折裂的不足。 目的：对比两种偶联剂改性的纳米SiO₂颗粒对聚甲基丙烯酸甲酯材料的弯曲强度、弯曲弹性模量和硬度改变。 方法：将两种偶联剂KH-570和KH-502改性的纳米SiO₂颗粒按质量比3%加入聚甲基丙烯酸甲酯粉体中制成(SiO₂/聚甲基丙烯酸甲酯)纳米复合材料。实验分为聚甲基丙烯酸甲酯材料、纳米SiO₂/聚甲基丙烯酸甲酯复合材料、KH-570-SiO₂/聚甲基丙烯酸甲酯复合材料、KH-502-SiO₂/聚甲基丙烯酸甲酯复合材料4组。 结果与结论：未经过偶联剂改性的纳米SiO₂/聚甲基丙烯酸甲酯复合材料与聚甲基丙烯酸甲酯材料相比,其弯曲强度、弯曲弹性模量和硬度差异无显著性意义(P > 0.05),而经过偶联剂改性的纳米SiO₂/聚甲基丙烯酸甲酯复合材料与聚甲基丙烯酸甲酯材料之间比较,其弯曲强度、弯曲弹性模量显著增强(P < 0.05),KH-502-SIO₂/PMMA组弯曲强度、弯曲弹性模量和硬度值显著大于与其他3组(P < 0.05)。结果表明,把经过偶联剂改性的纳米SiO2颗粒添加到聚甲基丙烯酸甲酯材料中制成SiO₂聚甲基丙烯酸甲酯复合材料,可使材料的弯曲强度、弯曲弹性模量和硬度明显提高。而经过偶联剂KH-502改性的纳米SiO₂聚甲基丙烯酸甲酯复合材料性能提高更为显著。     

影像增强剂对脑瘤螺旋断层放疗剂量计算的影响

目的:研究影像增强剂对脑瘤螺旋断层放疗(HT)计划剂量计算的影响,探讨使用定位CT增强图像替代平扫图像用于靶区勾画和剂量计算的临床可行性。方法:收集30例脑瘤病例,所有病例均在增强图像上勾画靶区和危及器官轮廓,再把靶区和危及器官轮廓复制到平扫图像上。在HT计划系统中分别以增强图像和平扫图像设计两组放疗计划,比较两组靶区和危及器官的CT值、剂量分布和治疗时间。结果:两组图像的CT值在瘤区域(PGTV)处具有统计学差异(P0.05),其他组织CT值比较无统计学差异;计划靶区和危及器官的剂量学、治疗时间等参数的差异比较均无统计学差异(P0.05)。结论:影像增强剂对脑瘤HT计划剂量计算影响极小,脑瘤放疗中可以使用定位CT增强图像替代定位CT平扫图像用于靶区勾画和螺旋断层放疗计划剂量计算。     

Surface modification of an experimental silicone rubber aimed at reducing initial candidal adhesion

Silicone rubber, which is a widely used biomaterial, is often used to make soft liners for permanent denture. Colonization of denture soft lining materials by Candida albicans can result in clinical problems. The aim of this study was to chemically modify the surface of an experimental silicone rubber in order to produce a silicone that was less susceptible to candidal colonization. Surface modification was carried out with the use of argon-plasma bombardment followed by silane treatment, which caused the incorporation of either hydrophilic or hydrophobic functional groups onto the surface. Changes in water contact angles and chemical analysis of the materials with scanning ion mass spectroscopy confirmed surface changes. In vitro assays were carried out using C. albicans to measure levels of adherence to the surface-modified silicone after 1 h. C. albicans exhibited very low adherence to all silane-treated surfaces, whether hydrophobic or hydrophilic. This led to the conclusion that incorporated long-chain functional groups were inhibiting the adherence of the yeast, possibly by the formation of a barrier between the surface of the material and the yeast. In conclusion, silane surface treatment of an experimental silicone rubber has been successful in reducing candidal adherence.     

丙烯酸树脂表面的不同方法对硅橡胶软衬的粘结效果的影响

目的 研究丙烯酸树脂表面的不同处理方法与硅橡胶软衬抗剪切强度及三点弯曲强度的影响。方法 制作50 mm×10 mm×3 mm的树脂片60片,并随机分为三组每组20片。将各组树脂片的粘结面（10 mm×10 mm）分别进行如下处理,A组为无特殊处理组,B组为单体处理组,C组为低温等离子体处理组。每组的两个树脂片粘结面间衬以2 mm的软衬材料,制成抗剪切强度试件,进行抗剪切强度测试。另制作64 mm×10 mm×3.3 mm树脂片30个,随机分为三组每组10个,处理方法同上,测试三点弯曲强度。结果 低温等离子体处理丙烯酸树脂与硅橡胶软衬的粘结强度高于单体处理组,差异有统计学意义（P<0.05）,对树脂的挠曲强度无影响,与对照组相比,差异无统计学意义（P＞0.05）,单体处理组三点弯曲强度,优于对照组,差异有统计学意义（P＜0.05)。结论 低温等离子体处理丙烯酸树脂比单体处理粘结强度提升的更高且不影响树脂的机械性能,为硅橡胶软衬的临床应用提供了更好的理论指导。     

松质骨移植材料孔隙率的显微CT和组织切片测试方法比较

目的采用显微 CT法和组织切片法对松质骨移植材料的孔隙率进行对比研究,为骨组织工程支架材料的研制和开发提供理论依据.方法首先取新鲜尸体的股骨和新鲜猪股骨,进行去除多余组织、灭菌、低温冷冻保存等处理后,制备成松质骨移植材料,使用显微 CT分别扫描同种异体骨和动物源性猪骨移植材料获取显微 CT图像.然后对同种异体松质骨组织进行染色和切片等处理,制备成同种异体骨组织切片材料,显微镜下观察骨组织切片并获取其图像,各取10幅图像用于实验.设计matlab程序对所有图像进行灰度化、图像增强、二值化、移除干扰等处理,计算孔隙率的数值.结果显微CT和组织切片测试得到的同种异体松质骨孔隙率与动物源性猪松质骨孔隙率结果无显著性差异(P>0.05).结论显微 CT标本的制备较组织切片大为简化,可以无损地获取数据,并省去灰度化、图像增强、移除干扰等处理过程,比组织切片法测量松质骨孔隙率更加简便.     

Iron oxide nanoparticles as a drug delivery vehicle for MRI monitored magnetic targeting of brain tumors

This study explored the possibility of utilizing iron oxide nanoparticles as a drug delivery vehicle for minimally invasive, MRI-monitored magnetic targeting of brain tumors. In vitro determined hydrodynamic diameter of approximately 100 nm, saturation magnetization of 94 emicro/g Fe and T2 relaxivity of 43 s(-1)mm(-)(1) of the nanoparticles suggested their applicability for this purpose. In vivo effect of magnetic targeting on the extent and selectivity of nanoparticle accumulation in tumors of rats harboring orthotopic 9L-gliosarcomas was quantified with MRI. Animals were intravenously injected with nanoparticles (12 mg Fe/kg) under a magnetic field density of 0 T (control) or 0.4 T (experimental) applied for 30 min. MR images were acquired prior to administration of nanoparticles and immediately after magnetic targeting at 1h intervals for 4h. Image analysis revealed that magnetic targeting induced a 5-fold increase in the total glioma exposure to magnetic nanoparticles over non-targeted tumors (p=0.005) and a 3.6-fold enhancement in the target selectivity index of nanoparticle accumulation in glioma over the normal brain (p=0.025). In conclusion, accumulation of iron oxide nanoparticles in gliosarcomas can be significantly enhanced by magnetic targeting and successfully quantified by MR imaging. Hence, these nanoparticles appear to be a promising vehicle for glioma-targeted drug delivery.     

Engineered multifunctional nanomaterials for multimodal imaging of retinoblastoma cells in vitro

Multifunctional nanoparticles are next generation materials that can be simultaneously used for imaging, diagnosis, and delivery of drugs. However, materials intended for cancer diagnosis need to be investigated for its cell uptake, toxicity, and effectiveness. In the current work, we have synthesized fluorescent iron oxide nanoparticles and evaluated its efficacy against retinoblastoma cell imaging. The iron oxide nanoparticles were synthesized and stabilized using oleic acid. Sulforhodamine B was adsorbed onto albumin over the oleic acid-capped iron oxide nanoparticles. Our results demonstrated good cell uptake in a time-dependent manner and nanoparticles were found to localize in the cytosol. Further, the nanoparticles exhibited excellent negative contrast in magnetic resonance imaging (MRI) experiments and with no cytoxicity (5–100?μg/mL iron oxide nanoparticles) to both normal as well as cancer cells demonstrating its biocompatibility. Thus, this novel material integrates the ability to image tissues with high sensitivity by MRI and specifically visualize Y79 retinoblastoma cells by fluorescence imaging with no toxicity.     

Dose perturbations and image artifacts caused by carbon-coated ceramic and stainless steel fiducials used in proton therapy for prostate cancer

Image-guided radiation therapy using implanted fiducial markers is a common solution for prostate localization to improve targeting accuracy. However, fiducials that are typically used for conventional photon radiotherapy cause large dose perturbations in patients who receive proton radiotherapy. A proposed solution has been to use fiducials of lower atomic number (Z) materials to minimize this effect in tissue, but the effects of these fiducials on dose distributions have not been quantified. The objective of this study was to analyze the magnitude of the dose perturbations caused by select lower-Z fiducials (a carbon-coated zirconium dioxide fiducial and a plastic-coated stainless steel fiducial) and compare them to perturbations caused by conventional gold fiducials. Sets of phantoms were used to assess select components of the effects on dose. First, the fiducials were assessed for radiographic visibility using both conventional computed tomography (CT) and an on-board kilovoltage imaging device at our proton therapy center. CT streak artifacts from the fiducials were also measured in a separate phantom. Second, dose perturbations were measured downstream of the fiducials using radiochromic film. The magnitude of dose perturbation was characterized as a function of marker material, implantation depth and orientation with respect to the beam axis. The radiographic visibility of the markers was deemed to be acceptable for clinical use. The dose measurements showed that the perpendicularly oriented zirconium dioxide and stainless steel fiducials located near the center of modulation of the proton beam perturbed the dose by less than 10%, but that the same fiducials in a parallel orientation near the end of the range of the beam could perturb the dose by as much as 38%. This suggests that carbon-coated and stainless steel fiducials could be used in proton therapy if they are located far from the end of the range of the beam and if they are oriented perpendicular to the beam axis.     

Microbial exopolysaccharide-mediated synthesis and stabilization of metal nanoparticles

Exopolysaccharides (EPSs) are structurally and functionally valuable biopolymer secreted by different prokaryotic and eukaryotic microorganisms in response to biotic/abiotic stresses and to survive in extreme environments. Microbial EPSs are fascinating in various industrial sectors due to their excellent material properties and less toxic, highly biodegradable, and biocompatible nature. Recently, microbial EPSs have been used as a potential template for the rapid synthesis of metallic nanoparticles and EPS-mediated metal reduction processes are emerging as simple, harmless, and environmentally benign green chemistry approaches. EPS-mediated synthesis of metal nanoparticles is a distinctive metabolism-independent bio-reduction process due to the formation of interfaces between metal cations and the polyanionic functional groups (i.e. hydroxyl, carboxyl and amino groups) of the EPS. In addition, the range of physicochemical features which facilitates the EPS as an efficient stabilizing or capping agents to protect the primary structure of the metal nanoparticles with an encapsulation film in order to separate the nanoparticle core from the mixture of composites. The EPS-capping also enables the further modification of metal nanoparticles with expected material properties for multifarious applications. The present review discusses the microbial EPS-mediated green synthesis/stabilization of metal nanoparticles, possible mechanisms involved in EPS-mediated metal reduction, and application prospects of EPS-based metal nanoparticles.