Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States.
Department of Chemistry, University of Wisconsin-Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States.
Anal Chem. 2017 Feb 7;89(3):1823-1830. doi: 10.1021/acs.analchem.6b04161. Epub 2017 Jan 10.
Polyelectrolyte (PE) wrapping of colloidal nanoparticles (NPs) is a standard method to control NP surface chemistry and charge. Because excess polyelectrolytes are usually employed in the surface modification process, it is critical to evaluate different purification strategies to obtain a clean final product and thus avoid ambiguities in the source of effects on biological systems. In this work, 4 nm diameter gold nanoparticles (AuNPs) were wrapped with 15 kDa poly(allylamine hydrochloride) (PAH), and three purification strategies were applied: (a) diafiltration or either (b) one round or (c) two rounds of centrifugation. The bacterial toxicity of each of these three PAH-AuNP samples was evaluated for the bacterium Shewanella oneidensis MR-1 and is quantitatively correlated with the amount of unbound PAH molecules in the AuNP suspensions, as judged by X-ray photoelectron spectroscopy, nuclear magnetic resonance experiments and quantification using fluorescent assay. Dialysis experiments show that, for a 15 kDa polyelectrolyte, a 50 kDa dialysis membrane is not sufficient to remove all PAH polymers. Together, these data showcase the importance of choosing a proper postsynthesis purification method for polyelectrolyte-wrapped NPs and reveal that apparent toxicity results may be due to unintended free wrapping agents such as polyelectrolytes.
聚电解质（PE）包裹胶体纳米粒子（NPs）是控制 NP 表面化学和电荷的标准方法。由于在表面改性过程中通常会使用过量的聚电解质，因此评估不同的纯化策略以获得纯净的最终产物至关重要，从而避免对生物系统影响的来源产生歧义。在这项工作中，直径为 4nm 的金纳米粒子（AuNPs）用 15kDa 聚（盐酸烯丙胺）（PAH）包裹，并应用了三种纯化策略：（a）渗滤或（b）一轮或（c）两轮离心。通过 X 射线光电子能谱、核磁共振实验和荧光测定定量评估这三种 PAH-AuNP 样品中的每一种对细菌 Shewanella oneidensis MR-1 的细菌毒性，并与 AuNP 悬浮液中未结合的 PAH 分子的量相关联。透析实验表明，对于 15kDa 的聚电解质，50kDa 的透析膜不足以去除所有的 PAH 聚合物。这些数据共同展示了为聚电解质包裹的 NPs 选择适当的后合成纯化方法的重要性，并表明明显的毒性结果可能是由于未预期的游离包裹剂（如聚电解质）所致。
