Skoglund Sara, Hedberg Jonas, Yunda Elena, Godymchuk Anna, Blomberg Eva, Odnevall Wallinder Inger
KTH Royal Institute of Technology, Division of Surface and Corrosion Science, School of Chemical Science and Engineering, Stockholm, Sweden.
National Research Tomsk Polytechnic University, Tomsk, Russia.
PLoS One. 2017 Jul 27;12(7):e0181735. doi: 10.1371/journal.pone.0181735. eCollection 2017.
The zeta potential (ZP) is a parameter commonly used to characterize metal nanoparticles (NPs) in solution. Such determinations are for example performed in nanotoxicology since the ZP influences e.g. the interaction between cells and different biomolecules. Four case studies on different metal NPs (Cu and Zn NPs, and citrate capped Ag NPs) are presented in this study in order to provide guidance on how to accurately interpret and report ZP data. Solutions of high ionic strength (150 mM NaCl) induce a higher extent of particle agglomeration (elucidated with Ag NPs) when compared with conditions in 10 mM NaCl, which further complicates the prediction of the ZP due to e.g. sedimentation and broadening of the zeta potential distribution. The particle size is seldom included specifically in the standard ways of determining ZP (Hückel and Smoluchowski approximations). However corrections are possible when considering approximations of the Henry function. This was seen to improve the analysis of NPs, since there are cases when both the Hückel and the Smulochowski approximations are invalid. In biomolecule-containing cell media (BEGM), the signal from e.g. proteins may interfere with the measured ZP of the NPs. The intensity distribution of the ZP of both the blank solution and the solution containing NPs should hence be presented in addition to the mean value. Due to an increased ionic strength for dissolving of metal NPs (exemplified by Zn NPs), the released metal ions must be considered when interpreting the zeta potential measurements. In this work the effect was however negligible, as the particle size was several hundred nm, conditions that made the Smoluchowski approximation valid despite an increased ionic strength. However, at low ionic strengths (mM range) and small-sized NPs (tens of nm), the effect of released metal ions can influence the choice of model for determining the zeta potential. Sonication of particle dispersions influences not only the extent of metal release but also the outermost surface oxide composition, which often results in an increased ZP. Surface compositional changes were illustrated for sonicated and non-sonicated Cu NPs. In all, it can be concluded that accurate measurements and interpretations are possible in most cases by collecting and reporting complementary data on characteristics such as particle size, ZP distributions, blank sample information, and particle oxide composition.
zeta电位（ZP）是常用于表征溶液中金属纳米颗粒（NPs）的一个参数。例如，在纳米毒理学中会进行此类测定，因为ZP会影响细胞与不同生物分子之间的相互作用等。本研究展示了四个关于不同金属纳米颗粒（铜和锌纳米颗粒以及柠檬酸盐包覆的银纳米颗粒）的案例研究，以便为如何准确解释和报告ZP数据提供指导。与10 mM NaCl条件相比，高离子强度（150 mM NaCl）的溶液会导致更高程度的颗粒团聚（以银纳米颗粒为例说明），这由于沉降和zeta电位分布变宽等原因，进一步使ZP的预测变得复杂。在确定ZP的标准方法（休克尔和斯莫卢霍夫斯基近似法）中，很少专门考虑颗粒大小。然而，在考虑亨利函数近似时可以进行校正。这被认为可以改进对纳米颗粒的分析，因为存在休克尔近似法和斯莫卢霍夫斯基近似法都无效的情况。在含有生物分子的细胞培养基（BEGM）中，例如蛋白质发出的信号可能会干扰所测量的纳米颗粒的ZP。因此，除了平均值外，还应呈现空白溶液和含有纳米颗粒的溶液的ZP强度分布。由于溶解金属纳米颗粒（以锌纳米颗粒为例）时离子强度增加，在解释zeta电位测量结果时必须考虑释放出的金属离子。然而在本研究中，这种影响可以忽略不计，因为颗粒大小为几百纳米，在这种情况下，尽管离子强度增加，斯莫卢霍夫斯基近似法仍然有效。然而，在低离子强度（毫摩尔范围）和小尺寸纳米颗粒（几十纳米）的情况下，释放出的金属离子的影响会影响确定zeta电位的模型选择。颗粒分散体的超声处理不仅会影响金属释放的程度，还会影响最外层表面氧化物的组成，这通常会导致ZP升高。对超声处理和未超声处理的铜纳米颗粒展示了表面组成的变化。总之，可以得出结论，通过收集和报告关于颗粒大小、ZP分布、空白样品信息和颗粒氧化物组成等特征的补充数据，在大多数情况下可以进行准确的测量和解释。
