基于新型离子载体的钙离子选择性电极和光极研究

钙离子（Ca²⁺）作为细胞间传达信息的第二信使，参与了多项重要的生命活动，它的检测在环境、化学生物、工业等领域具有重要意义。在常见钙离子检测方式中，离子选择性电极（ISE）具有长期的可靠性、高灵敏度和准确性，而离子选择性光极（ISO）成本低廉、简便直观，二者均是当下钙离子传感器的研究热点。无论是ISE还是ISO，对Ca²⁺的选择性传感都高度依赖于钙离子载体的使用，而目前商业钙离子载体数目相对较少，研究进展相对缓慢，新型离子选择性传感器的开发受限，成本较高。本论文拟通过了解钙离子载体设计规则，结合潜在离子载体结构，设计合成在常见阳离子中对Ca²⁺有良好响应性和选择性的低成本新型钙离子载体，并探究它们在离子选择性电极和光极中的应用。

设计合成并表征了三个离子载体NDB-1、NDB-2和NDB-3。在以Ca²⁺为目标检测离子时，NDB-1和NDB-3离子选择性电极线性响应区间10^-6–10^-1 M，电极的实际响应斜率为25.3 mV dec^-1和26.7 mV dec^-1，NDB-2离子选择性电极线性响应区间10^-5–10^-1 M，电极响应斜率24.7 mV dec^-1。NDB-1的Ca²⁺选择性和响应性最佳，络合常数对数为9.95±0.08。NDB-1与2-硝基苯辛醚（NPOE）制备的离子选择性电极膜，成功检测稀释10倍胎牛血清中的Ca²⁺，含量为3.16 mol/L，相对误差4.2%。NDB-1合成简单、原料廉价，制备的离子选择性电极可实现常见阳离子中良好的钙离子选择性，并实现实际样品检测，它作为离子载体在电化学检测钙离子领域具有广阔的应用前景。

上述的三个离子载体也用于制备基于生色离子载体的钙离子选择性纳米颗粒传感器，它们分别作为钙离子载体与pH指示剂生色离子载体Ⅰ、离子交换剂四苯基硼酸钠（NaTFPB）组成钙离子选择性光极。其中，基于NDB-1构建的钙离子选择性纳米传感器响应性最好，实现了平衡模式下的钙离子传感。NDB-1基于通过计算，NDB-1通常与Ca²⁺以2:1摩尔比络合，该钙离子选择性传感颗粒响应区间为10^-5–10^-1 M，在常见阳离子中对Ca²⁺具有良好的选择性。NDB-1制备的离子选择性光极对也能展现良好的钙离子选择性，并且光极为平衡响应模式，可以实现较宽的检测区间，NDB-1作为新型钙离子载体在离子选择性光极中也极具应用潜力。

Calcium ions (Ca²⁺) play a crucial role as second messengers in intercellular communication, participating in vital life activities. Their detection is of significant importance in the fields of environment, chemical biology, and industry. Among common methods for calcium ion detection, ion-selective electrodes are known for their long-term reliability, high sensitivity, and accuracy. Ion-selective optodes are cost-effective, simple, and intuitive, making them a hot topic in current research on calcium ion sensors. However, the number of commercially available calcium ionophores is relatively limited, the research progress has been sluggish. The development of new ion-selective sensors is constrained and costs are high. This paper, by understanding the design rules of calcium ionophores and combining potential ionic structures, has designed and synthesized a new type of calcium ionophore that exhibits good responsiveness and selectivity for calcium ions among common cations. Both ion-selective electrodes and optodes demonstrate these characteristics at a low cost.

Three potential ionophore have been designed, synthesized, and characterized by us, named NDB-1, 2, and 3. When used as calcium ionophore, the linear response range of the NDB-1 and NDB-3 ion-selective electrodes was between 10^-6 M and 10^-1 M, with response slopes of 25.3 mV dec^-1 and 26.7 mV dec^-1, respectively. The NDB-2 ion-selective electrode had a linear response range between 10^-5 M and 10^-1 M, with a response slope of 24.7 mV dec^-1. The ionophore with the best selectivity and responsiveness for calcium ion detection was identified as NDB-1, with a complex constant log of 9.95±0.08. The NPOE ion-selective electrode membrane prepared with NDB-1 successfully detected the calcium ion content in diluted (by 10 times) fetal bovine serum at 3.16 mol/L, with a relative error of 4.2%. NDB-1 is simple to synthesize and cheap in raw materials. It has good calcium ion selectivity among common cations. As an ionophores, it has broad prospects and application value in the field of electrochemical detection of calcium ions.

The three types of potential ionophores mentioned above were formulated into calcium ion-selective optodes based on chromoionophores. NDB-1, NDB-1 typically complexes with calcium ions at a molar ratio of 2:1. Enables it to serve as a calcium ionophores in combination with the pH indicator chromoionophore I and the ion-exchanger NaTFPB, constituting an ion-selective optode. This arrangement facilitates the optode's selective sensing of calcium ions in a balanced mode, leveraging the specific recognition properties of the ionophore, showed a response range of 10^-5 M to 10^-1 M and exhibited high selectivity for calcium ions among common cations. The ion-selective optode prepared by NDB-1 can also exhibit good calcium ion selectivity, and the optode adopts a balanced response mode, which can achieve a wider detection range. Thus, NDB-1, as a novel calcium ionophores, also has great application potential in ion-selective optodes.

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