AbstractLigand 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 × 102 cfu·mL−1 in a short time (within 15 min), and the working range is 1 × 102 to 1 × 106 cfu·mL−1, which is superior over the detection performance of conventional test strip using AuNRs modified by centrifugation. Graphical abstractSchematic 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.

中文翻译：

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金纳米棒上的透析辅助配体交换：E.coli O157:H7 侧流免疫测定性能的放大

摘要金纳米棒（AuNRs）表面的配体交换被广泛应用，但常规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）。这会导致非预期的 AuNR 聚集。这里描述了透析辅助协议，用于 AuNRs 上的配体交换。由浓度梯度驱动的透析被证明是从水溶液中分离 CTAB 的有力工具。透析袋中 CTAB 的浓度梯度可以避免因环境剧烈变化而导致的 AuNRs 可能聚集。它还支持 AuNRs 表面配体交换的速率。修饰的 AuNR 用于食品病原体大肠杆菌 O157:H7 的侧流测试条免疫测定 (LFTS-IA)，以研究配体交换的效率。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 在 LFTS-IAs 的测试线中显示出与抗体的结合改善和增强的视觉信号。使用便携式条形阅读器（吸收波长 = 525 nm）记录测试结果。透析修饰的AuNRs的灵敏度在短时间内（15分钟内）甚至可以低至1×102 cfu·mL-1，工作范围为1×102至1×106 cfu·mL-1，其检测性能优于使用通过离心改性的 AuNRs 的常规试纸条的检测性能。图形摘要 AuNRs 配体交换的示意图。AuNRs 在水中透析以降低 CTAB 浓度。然后，11-巯基十一烷酸 (MUA) 取代了覆盖在 AuNRs 表面的 CTAB。改良的 AuNRs 被用于大肠杆菌 O157:H7 的侧流免疫分析。