This study explores the potential of seven ferrocenyl (Fc) compounds with cross-linking groups as alternative redox labels to methylene blue (MB) for electrochemical aptamer-based (E-AB) sensors. The cross-linking efficiency, formal potential (E⁰′), and electrochemical durability of these compounds were evaluated. Compound Fc1a-X exhibited superior performance, characterized by efficient cross-linking, a moderate and pH-insensitive E⁰′, and enhanced durability during repeated potential scans. The attachment of Fc1a-X, which includes a 3-carbon chain spacer and an N-hydroxysuccinimide-ester cross-linking group, to an amine-terminated monolayer on a Au electrode demonstrated high cross-linking efficiency, which is critical for achieving high sensitivity. The E⁰′ of Fc1a-X attached to the aptamer monolayer was 0.14 V, which is within the optimal range of −0.2 to 0.2 V vs Ag/AgCl. Square wave voltammetry showed that the peak potential and current of Fc1a-X are pH-insensitive, which is critical for versatile use. In serum, Fc1a-X maintained stable peak current levels without a gradual decrease after an initial rapid decrease during the first 2 h with considerably less reduction over 12 h compared to MB. Using Fc1a-X as the redox label, an E-AB sensor effectively detected doxorubicin in serum, covering the clinical range. These findings suggest Fc1a-X as a promising candidate for developing robust, versatile, and sensitive E-AB sensors.

中文翻译：

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铁烯基化合物作为替代氧化还原标记物，用于稳定且多功能的基于电化学适配体的传感器


本研究探讨了七种具有交联基团的二茂铁 （Fc） 化合物作为亚甲基蓝 （MB） 的替代氧化还原标记的潜力，用于基于电化学适配体 （E-AB） 传感器。评估了这些化合物的交联效率、形式电位 （E⁰′） 和电化学耐久性。化合物 Fc1a-X 表现出卓越的性能，其特点是高效交联、中等且对 pH 不敏感的 E⁰'，以及在重复电位扫描期间增强的耐用性。Fc1a-X（包括 3 碳链间隔子和 N-羟基琥珀酰亚胺酯交联基团）与 Au 电极上的胺封端单分子层的连接表现出高交联效率，这对于实现高灵敏度至关重要。附着在适配体单层上的 Fc1a-X 的 E⁰' 为 0.14 V，与 Ag/AgCl 相比，在 −0.2 至 0.2 V 的最佳范围内。方波伏安法表明，Fc1a-X 的峰值电位和电流对 pH 值不敏感，这对于多种用途至关重要。在血清中，Fc1a-X 在前 2 小时内最初快速下降后保持稳定的峰值电流水平，没有逐渐降低，与 MB 相比，在 12 小时内降低幅度明显减少。使用 Fc1a-X 作为氧化还原标记，E-AB 传感器有效检测血清中的阿霉素，覆盖临床范围。这些发现表明 Fc1a-X 是开发稳健、多功能和灵敏的 E-AB 传感器的有前途的候选者。