Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
Langmuir. 2009 Dec 1;25(23):13384-93. doi: 10.1021/la9019734.
Nanoparticles with monodisperse, spherical magnetic iron oxide cores and contiguous gold shells (Fe/Au NPs) have been synthesized in order to combine magnetophoretic responsiveness and localized surface plasmon resonance in a single nanoparticle. Such particles are sufficiently charged to be stable against flocculation 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 are used to monitor the colloidal stability of Fe/Au NPs in pH 7.4 phosphate buffered saline containing 154 mM NaCl (PBS). While uncoated particles flocculate immediately upon introduction to PBS, Fe/Au NPs with adsorbed layers of bovine serum albumin or the amphiphilic triblock copolymers Pluronic F127 and Pluronic F68 resist flocculation after more than 5 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 6000 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 Derjaguin-Landau-Verwey-Overbeek (DLVO) theory predictions of interparticle interactions.
为了将磁泳响应性和局域表面等离子体共振结合在单个纳米粒子中，合成了具有单分散、球形磁性氧化铁核和连续金壳的纳米粒子（Fe/Au NPs）。这些粒子带足够的电荷，在低离子强度介质中稳定，不会聚沉，但需要进行表面修饰，才能在适合生物技术应用的高离子强度介质中稳定分散。动态光散射和紫外-可见分光光度法用于监测在含有 154 mM NaCl（PBS）的 pH 7.4 磷酸盐缓冲盐水中的 Fe/Au NPs 的胶体稳定性。未涂层的颗粒在引入 PBS 时立即聚沉，而吸附了牛血清白蛋白或两亲性三嵌段共聚物 Pluronic F127 和 Pluronic F68 的 Fe/Au NPs 在 PBS 中超过 5 天后仍能抵抗聚沉。吸附的葡聚糖允许形成小的聚集体，但分子量在 6000 到 100000 之间的聚乙二醇均聚物不能作为有效的空间稳定剂。吸附的 Pluronic 共聚物作为空间稳定剂的有效性是根据测量的吸附层厚度和扩展的德加古因-兰德au-Verwey-Overbeek（DLVO）理论预测的颗粒间相互作用来解释的。
