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Design and synthesis of magnetic nanoparticles with gold shells for single particle optical tracking.

机译：具有金壳的磁性纳米粒子的设计和合成，用于单粒子光学跟踪。

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The design, synthesis, and characterization of iron oxide core, gold shell nanoparticles are studied in this thesis. Firstly, nanoparticles with 18 +/- 1.7 nm diameter iron oxide cores with ∼5 nm thick gold shells were synthesized via a new seed-mediated electroless deposition method. The nanoparticles were superparamagnetic at room temperature and could be reversibly collected by a permanent magnet. These nanoparticles displayed a sharp localized surface plasmon resonance peak at 605 nm, as predicted by scattering theory, and their large scattering cross-section allowed them to be individually resolved in darkfield optical microscopy while undergoing Brownian motion in aqueous suspension.;Later, commercially available 38 +/- 3.8 nm diameter spherical iron oxide nanoparticles (from Ocean Nanotech, Inc) were employed to make core-shell particles. These particles were decorated with cationic poly(diallyldimethylammonium chloride) (PDDA) which further promotes the attachment of small gold clusters. After gold seeding, the average hydrodynamic diameter of the core-shell particles is 172 +/- 65.9 nm. The magnetophoretic motion of these particles was guided by a piece of magnetized mu-metal. Individual particle trajectories were observed by darkfield optical microscopy. The typical magnetophoretic velocity achieved was within the range of 1--10 mum/sec. Random walk analysis performed on these particles while undergoing Brownian motion confirmed that individual particles were indeed being imaged. The particle size variation within the observed sample obtained through random walk analysis was within the size distribution obtained by dynamic light scattering. When the current to the solenoid used to magnetize the mu-metal was turned off, all the collected core-shell particles were readily redispersed by diffusion back into the surrounding environment.;A Peclet number analysis was performed to probe the convective motion of nanospheres and nanorods under the influence of magnetophoresis and diffusion. Under most circumstances, magnetophoretic behavior dominates diffusion for nanorods, as the magnetic field lines tend to align the magnetic moment along the rod axis. The synthesis and dispersion of fluorophore-tagged nanorods are described. Fluorescence microscopy was employed to image the nanorod motion in a magnetic field gradient. The preliminary experimental data are consistent with the Peclet number analysis.;Lastly, the colloidal stability of iron oxide core, gold shell nanoparticles in high ionic strength media was investigated. Such particles are sufficiently charged to be stable against flocculation without modification in low ionic strength media, but they require surface modification to be stably dispersed in elevated ionic strength media that are appropriate for biotechnological applications. Dynamic light scattering and ultraviolet-visible spectrophotometry were used to monitor the colloidal stability of core-shell particles in pH 7.4, 150 mM ionic strength phosphate buffered saline (PBS). While uncoated particles flocculated immediately upon being introduced into PBS, core-shell particles with adsorbed layers of bovine serum albumin or the amphiphilic triblock copolymers Pluronic F127 and Pluronic F68 resist flocculation after more than five days in PBS. Adsorbed dextran allowed flocculation that was limited to the formation of small clusters, while poly(ethylene glycol) homopolymers ranging in molecular weight from 6,000 to 100,000 were ineffective steric stabilizers. The effectiveness of adsorbed Pluronic copolymers as steric stabilizers was interpreted in terms of the measured adsorbed layer thickness and extended DLVO theory predictions of the interparticle interactions.
机译：本文研究了氧化铁核，金壳纳米粒子的设计，合成及表征。首先，通过一种新的种子介导的化学沉积方法，合成了具有18 +/- 1.7 nm直径的氧化铁核和约5 nm厚的金壳的纳米粒子。纳米粒子在室温下是超顺磁性的，并且可以被永磁体可逆地收集。如散射理论所预测，这些纳米粒子在605 nm处显示出一个尖锐的局部表面等离子体共振峰，并且它们的大散射截面使它们可以在暗视野光学显微镜中单独分辨，同时在水性悬浮液中进行布朗运动。使用直径为38 +/- 3.8 nm的球形氧化铁纳米颗粒（来自Ocean Nanotech，Inc）来制备核-壳颗粒。这些颗粒用阳离子聚（二烯丙基二甲基氯化铵）（PDDA）修饰，这进一步促进了小金簇的附着。接种金后，核-壳颗粒的平均流体动力学直径为172 +/- 65.9 nm。这些颗粒的磁致运动由一块磁化的mu-金属引导。通过暗场光学显微镜观察单个粒子的轨迹。获得的典型磁致速度在1--10mum / sec的范围内。在经历布朗运动的同时对这些粒子执行随机游走分析，确认单个粒子确实在成像。通过随机游走分析获得的观察样品内的粒径变化在通过动态光散射获得的粒径分布内。当用于使mu-metal磁化的螺线管的电流关闭时，所有收集的核-壳颗粒都容易通过扩散回到周围环境而重新分散。;进行了Peclet数分析以探测纳米球和对流的对流运动。磁致伸缩和扩散的影响下的纳米棒。在大多数情况下，由于磁场线倾向于沿磁棒轴对齐磁矩，因此磁致伸缩行为主导了纳米棒的扩散。描述了荧光团标记的纳米棒的合成和分散。荧光显微镜用于在磁场梯度中成像纳米棒的运动。初步的实验数据与Peclet数分析相符。最后，研究了高离子强度介质中氧化铁核，金壳纳米粒子的胶体稳定性。这样的颗粒被充分带电以稳定地抗絮凝而不在低离子强度介质中进行改性，但是它们要求表面改性以稳定地分散在适于生物技术应用的升高的离子强度介质中。动态光散射和紫外可见分光光度法用于监测核壳颗粒在pH 7.4、150 mM离子强度磷酸盐缓冲盐水（PBS）中的胶体稳定性。当未包被的颗粒在被引入PBS后立即发生絮凝时，带有牛血清白蛋白或两亲性三嵌段共聚物Pluronic F127和Pluronic F68吸附层的核-壳颗粒在PBS中放置超过五天后仍能抗絮凝。吸附的右旋糖酐允许的絮凝仅限于小簇的形成，而分子量从6,000到100,000的聚（乙二醇）均聚物是无效的空间稳定剂。吸附的Pluronic共聚物作为空间稳定剂的有效性是根据测得的吸附层厚度和对颗粒间相互作用的扩展DLVO理论预测进行解释的。

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