Citrate-capped gold nanoparticles (AuNPs) are highly important for sensing, drug delivery, and materials design. Many of their reactions take place in various buffers such as phosphate and Good's buffers. The effect of buffer on the surface properties of AuNPs is critical, yet this topic has not been systematically explored. Herein, we used halides such as fluoride, chloride, and bromide as probes to measure the relative adsorption strength of six common buffers. Among them, HEPES had the highest adsorption affinity, while MES, citrate and phosphate were weakly adsorbed with an overall ranking of HEPES > PIPES > MOPS > MES > citrate, phosphate. The adsorption strength was reflected from the inhibited adsorption of DNA and from the displacement of pre-adsorbed DNA. This conclusion is also supported by surface enhanced Raman spectroscopy. Furthermore, some buffer molecules did not get adsorbed instantaneously, and the MOPS buffer took up to 1 h to reach equilibrium. Finally, a classic label-free AuNP-based colorimetric sensor was tested. Its sensitivity increased by 15.7-fold when performed in a MES buffer compared to a HEPES buffer. This study has articulated the importance of buffer for AuNP-based studies and how it can improve sensors and yield more reproducible experimental systems.

中文翻译：

---

Good's缓冲液对调节荧光和比色DNA感应的金纳米颗粒具有多种亲和力

柠檬酸盐覆盖的金纳米颗粒（AuNPs）对于传感，药物输送和材料设计非常重要。它们的许多反应在各种缓冲液中发生，例如磷酸盐和Good's缓冲液。缓冲剂对AuNPs表面性能的影响至关重要，但尚未系统地探讨该主题。在本文中，我们使用氟化物，氯化物和溴化物等卤化物作为探针来测量六种常见缓冲液的相对吸附强度。其中，HEPES具有最高的吸附亲和力，而MES，柠檬酸盐和磷酸盐的吸附较弱，总体排名为HEPES> PIPES> MOPS> MES>柠檬酸盐，磷酸盐。吸附强度由抑制的DNA吸附和预吸附DNA的置换反映。表面增强拉曼光谱也支持该结论。此外，一些缓冲分子没有立即被吸附，MOPS缓冲液要花费1小时才能达到平衡。最后，测试了经典的无标签基于AuNP的比色传感器。与HEPES缓冲区相比，在MES缓冲区中执行时，其灵敏度提高了15.7倍。这项研究阐明了缓冲液对于基于AuNP的研究的重要性，以及缓冲液如何改善传感器并产生可重复性更高的实验系统。