Institute of Surface/Interface Science and Technology, Key Laboratory of Superlight Material and Surface Technology of Ministry of Education, College of Materials Science and Chemical Engineering , Harbin Engineering University , Harbin 150001 , China.
Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Key Laboratory of Molecular Nanostructure and Nanotechnology , Institute of Chemistry, the Chinese Academy of Sciences (CAS) , Beijing 100190 , China.
Anal Chem. 2019 Apr 2;91(7):4421-4428. doi: 10.1021/acs.analchem.8b04944. Epub 2019 Mar 14.
In vivo monitoring of extracellular calcium ion (Ca) is of great importance due to its significant contributions in different (patho)physiological processes. In this study, we develop a potentiometric method with solid-state ion-selective electrodes (ISEs) for in vivo monitoring of the dynamics of the extracellular Ca by using hollow carbon nanospheres (HCNs) as a transducing layer and solid contact to efficiently promote the ion-to-electron transduction between an ionophore-doped solvated polymeric membrane and a conducting substrate. We find that the use of HCNs essentially improves the stability of the signal response and minimizes the potential drift of the as-prepared ISEs. With three-shelled HCNs (3s-HCNs) as the transducing layer, we fabricate a solid-state Ca-selective microelectrode by forming a Ca-selective membrane with calcium ionophore II as the recognition unit, 2-nitrophenyl octyl ether as the plasticizer, sodium tetrakis[3,5-bis(trifluoromethyl)phenyl] borate as the ion exchanger, and polyvinyl chloride polymeric as the matrix onto the 3s-HCN-modified carbon fiber electrodes. The as-prepared electrode shows a high stability and a near Nernst response of 28 mV/decade toward Ca over a concentration range from 10 to 0.05 M as well as a good selectivity against species endogenously existing in the central nervous system. With these properties, the electrode is used for real-time recording of the dynamics of extracellular Ca during spreading depression induced by electrical stimulation, in which the extracellular Ca in rat cortex is found to decrease by 50.0 ± 7.5% ( n = 5) during spreading depression. This study essentially offers a new platform to develop solid-state ISEs, which is particularly useful for in vivo measurements of metal ions and pH in live rat brain.
由于细胞外钙离子 (Ca) 在不同的（病理）生理过程中的重要贡献，因此对其进行体内监测具有重要意义。在本研究中，我们开发了一种使用固态离子选择性电极 (ISE) 的电位法，通过空心碳纳米球 (HCN) 作为转换层和固态接触，有效地促进了离子载体掺杂的溶剂化聚合物膜和导电基底之间的离子到电子的转换，从而实现对细胞外 Ca 动力学的体内监测。我们发现，使用 HCN 可以从本质上提高信号响应的稳定性，并最小化所制备的 ISE 的电位漂移。使用三壳空心碳纳米球 (3s-HCN) 作为转换层，我们通过形成以钙离子载体 II 为识别单元、2-硝基苯辛醚为增塑剂、四(3,5- 二氟苯基)硼酸钠为离子交换剂、聚氯乙烯聚合物为基质的钙选择性膜，在 3s-HCN 修饰的碳纤维电极上制备了固态 Ca 选择性微电极。所制备的电极表现出高稳定性和对 Ca 的近 Nernst 响应，其浓度范围为 10 至 0.05 M，斜率为 28 mV/decade，对中枢神经系统中内源性存在的物质具有良好的选择性。具有这些特性的电极可用于实时记录电刺激诱导的扩布性去极化期间细胞外 Ca 的动力学，其中在扩布性去极化期间，大鼠皮质中的细胞外 Ca 被发现降低了 50.0±7.5%（n=5）。这项研究为开发固态 ISE 提供了一个新的平台，对于在活体大鼠脑中进行金属离子和 pH 值的体内测量尤其有用。
