Institute of Nanomedicine and Nanobiosensing, MOE Key Laboratory for Analytical Science of Food Safety and Biology, Fujian Provincial Key Laboratory of Analysis and Detection Technology for Food Safety, College of Chemistry, Fuzhou University, Fuzhou, 350116, China.
Division of Polymer and Composite Materials, Ningbo Institute of Material Technology and Engineering Chinese Academy of Sciences, No. 1219 Zhongguan West Road, Zhenhai District, Ningbo, 315201, China.
Mikrochim Acta. 2018 Jul 2;185(7):350. doi: 10.1007/s00604-018-2897-0.
Ligand exchange on the surface of gold nanorods (AuNRs) is widely used, but conventional methods usually require multiple centrifugation cycles to completely remove cetyltrimethylammonium bromide (CTAB). This can lead to undesired aggregation of AuNRs. A dialysis-assisted protocol is described here for ligand exchange on AuNRs. Dialysis driven by a concentration gradient is shown to be a powerful tool to separate CTAB from aqueous solutions. The concentration gradient of CTAB in a dialysis bag can avoid the possible aggregation of AuNRs that can be caused by drastic environmental changes. It also supports the rate of ligand exchange on the surfaces of the AuNRs. The modified AuNRs were employed in a lateral-flow test strip immunoassay (LFTS-IAs) for the food pathogen E. coli O157:H7 in order to study of efficiency of ligand exchange. Compared to AuNRs where ligand exchange was performed via multiple centrifugation cycles, the AuNRs prepared by dialysis-assisted ligand exchange show improved conjugation to antibody and enhanced visual signals in the test line of the LFTS-IAs. A portable strip reader (absorption wavelength = 525 nm) is used to records the testing results. The sensitivity of AuNRs modified by dialysis has been achieved even as low as 1 × 10 cfu·mL in a short time (within 15 min), and the working range is 1 × 10 to 1 × 10 cfu·mL, which is superior over the detection performance of conventional test strip using AuNRs modified by centrifugation. Graphical abstract Schematic presentation of the ligand exchange of AuNRs. The AuNRs were dialysed in water to decrease the CTAB concentration. Then, 11-mercaptoundecanoic acid (MUA) replaces the CTAB capped on the surface of AuNRs. The modified AuNRs were employed in a lateral flow immunoassay for E. coli O157:H7.
金纳米棒（AuNRs）表面的配体交换被广泛应用，但传统方法通常需要多次离心循环才能完全去除十六烷基三甲基溴化铵（CTAB）。这可能导致 AuNRs 不期望的聚集。本文描述了一种用于 AuNRs 配体交换的透析辅助方案。通过浓度梯度驱动的透析被证明是一种从水溶液中分离 CTAB 的强大工具。透析袋中 CTAB 的浓度梯度可以避免由于环境变化剧烈而可能导致 AuNRs 聚集。它还支持 AuNRs 表面配体交换的速率。修饰后的 AuNRs 用于侧向流动测试条免疫分析（LFTS-IAs）以研究配体交换效率。与通过多次离心循环进行配体交换的 AuNRs 相比，通过透析辅助配体交换制备的 AuNRs 显示出与抗体更好的缀合以及 LFTS-IAs 测试线上的增强视觉信号。使用便携式条带读取器（吸收波长 = 525nm）记录测试结果。通过透析修饰的 AuNRs 的灵敏度甚至可以达到低至 1×10 cfu·mL 在短时间内（15 分钟内），工作范围为 1×10 到 1×10 cfu·mL，优于使用离心法修饰的 AuNRs 的常规测试条的检测性能。
