Jensen Isabel M, Clark Vincent, Kirby Harper L, Arroyo-Currás Netzahualcóyotl, Jenkins David M
Department of Chemistry University of Tennessee Knoxville Knoxville TN 37996 USA
Chemistry-Biology Interface Program Johns Hopkins University Baltimore MD 21218 USA.
Mater Adv. 2024 Aug 15;5(17):7052-7060. doi: 10.1039/d4ma00648h. eCollection 2024 Aug 27.
Self-assembled monolayers (SAMs) are employed in electrochemical biosensors to passivate and functionalize electrode surfaces. These monolayers prevent the occurrence of undesired electrochemical reactions and act as scaffolds for coupling bioaffinity reagents. Thiols are the most common adlayer used for this application; however, the thiol-gold bond is susceptible to competitive displacement by naturally occurring solvated thiols in biological fluids, as well as to desorption under continuous voltage interrogation. To overcome these issues, N-heterocyclic carbene (NHC) monolayers have been proposed as an alternative for electrochemical biosensor applications due to the strong carbon-gold bond. To maximize the effectiveness of NHCs for SAMs, a thorough understanding of both the steric effects of wingtip substituents and NHC precursor type to the passivation of electrode surfaces is required. In this study, five different NHC wingtips as well as two kinds of NHC precursors were evaluated. The best performing NHC adlayers can be cycled continuously for four days (over 30 000 voltammetric cycles) without appreciably desorbing from the electrode surface. Benchmark thiol monolayers, in contrast, rapidly desorb after only twelve hours. Investigations also show NHC adlayer formation on other biosensor-relevant electrodes such as platinum and palladium.
自组装单分子层（SAMs）用于电化学生物传感器，以钝化电极表面并使其功能化。这些单分子层可防止不期望的电化学反应发生，并作为偶联生物亲和试剂的支架。硫醇是用于此应用的最常见吸附层；然而，硫醇 - 金键易受生物流体中天然存在的溶剂化硫醇的竞争性取代影响，并且在连续电压检测下会发生解吸。为克服这些问题，由于碳 - 金键较强，已提出将N - 杂环卡宾（NHC）单分子层用作电化学生物传感器应用的替代方案。为了使NHC对SAMs的有效性最大化，需要深入了解翼尖取代基的空间效应以及NHC前体类型对电极表面钝化的影响。在本研究中，评估了五种不同的NHC翼尖以及两种NHC前体。性能最佳的NHC吸附层可以连续循环四天（超过30000次伏安循环）而不会明显从电极表面解吸。相比之下，基准硫醇单分子层仅在十二小时后就迅速解吸。研究还表明NHC吸附层可在其他与生物传感器相关的电极（如铂和钯）上形成。
