Poly(3,4-ethylenedioxythiophene) (PEDOT) has been widely studied in recent decades due to its high stability, biocompatibility, low redox potential, moderate band gap, and optical transparency in its conducting state. However, for its long-term in vivo applications, the biocompatibility of PEDOT still need to be improved. To address this challenge, zwitterionic Poly(sulfobetaine 3,4-ethylenedioxythiophene) (PSBEDOT) that contains EDOT backbone with sulfobetaine functional side chains were developed in our previous study. Although PSBEDOT showed great resistance to proteins, cells, and bacteria, it is still not clear how the zwitterionic sulfobetaine side chain affects the electrochemical properties of the polymer and reactivity of the monomer. To have better understanding on the structure-function relationship of zwitterionic conducting polymer, we synthesized two derivatives of PSBEDOT, PSBEDOT-4 and PSBEDOT-5, by introducing the alkoxyl spacer between EDOT and sulfobetaine. The interfacial impedance of PSBEDOT-4 and PSBEDOT-5 was examined by electrochemical impedance spectroscopy and showed significant improvement which is about 20 times lower than PSBEDOT on both gold and indium tin oxide substrates at 1 Hz. In the protein adsorption test, PSBEDOT, PSBEDOT-4 and PSBEDOT-5 exhibited comparable resistance to the fibrinogen solution. All three polymers had low protein adsorption around 3%-5% comparing to the control sample, PEDOT, which was normalized to 100%. Additionally, the morphology of PSBEDOT, PSBEDOT-4 and PSBEDOT-5 with different synthesis parameter have been investigated by scanning electron microscope. We believe that these stable and biocompatible materials can be good candidates for developing long-term bioelectronics devices.

Statement of significance

To address the challenges associated existing conducting materials for bioelectronics, we developed a versatile and high performance zwitterionic conducting material platform with excellent stability, electrochemical, antifouling and controllable antimicrobial/antifouling properties. In this work, we developed two high-performance conducting polymers and systematically investigated how its structure affect their properties. Our study shows we can accurately tune the molecular structure of the monomer to dramatically improve the performance of zwitterionic conducting polymer. This zwitterionic conducting polymer platform may dramatically increase the performance and service life of electrochemical devices for many long-term applications, such as implantable biosensing, tissue engineering, wound healing, robotic prostheses, biofuel cell etc., which all require high performance conducting materials with excellent antifouling/biocompatibility at complex biointerfaces.

中文翻译：

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聚（磺基甜菜碱3,4-乙撑二氧噻吩）（PSBEDOT）及其衍生物的结构功能研究

聚（3,4-乙撑二氧噻吩）（PEDOT）由于其高稳定性，生物相容性，低氧化还原电势，适度的带隙和导电状态下的光学透明性而在近几十年来得到了广泛的研究。但是，由于其长期体内存在在应用中，PEDOT的生物相容性仍有待提高。为了解决这一挑战，在我们先前的研究中开发了两性离子聚（磺基甜菜碱3,4-乙撑二氧噻吩）（PSBEDOT），其中含有具有磺基甜菜碱功能性侧链的EDOT主链。尽管PSBEDOT对蛋白质，细胞和细菌显示出极大的抵抗力，但尚不清楚两性离子磺基甜菜碱侧链如何影响聚合物的电化学性质和单体的反应性。为了更好地了解两性离子导电聚合物的结构-功能关系，我们通过在EDOT和磺基甜菜碱之间引入烷氧基间隔基，合成了PSBEDOT的两种衍生物PSBEDOT-4和PSBEDOT-5。通过电化学阻抗谱检查了PSBEDOT-4和PSBEDOT-5的界面阻抗，结果表明，在1 Hz的金和铟锡氧化物衬底上，PSBEDOT-4和PSBEDOT-5的界面阻抗均明显低于PSBEDOT的20倍。在蛋白质吸附测试中，PSBEDOT，PSBEDOT-4和PSBEDOT-5对纤维蛋白原溶液表现出可比的抗性。与归一化为100％的对照样品PEDOT相比，所有三种聚合物的蛋白质吸附率均较低，约为3％-5％。另外，通过扫描电子显微镜研究了合成参数不同的PSBEDOT，PSBEDOT-4和PSBEDOT-5的形貌。我们相信，这些稳定且具有生物相容性的材料可以成为开发长期生物电子设备的理想选择。

重要声明

为了解决与现有生物电子导电材料相关的挑战，我们开发了一种多功能，高性能的两性离子导电材料平台，具有出色的稳定性，电化学，防污和可控的抗菌/防污性能。在这项工作中，我们开发了两种高性能导电聚合物，并系统地研究了其结构如何影响其性能。我们的研究表明，我们可以准确地调整单体的分子结构，从而显着改善两性离子导电聚合物的性能。这种两性离子导电聚合物平台可以极大地延长许多长期应用中电化学装置的性能和使用寿命，例如可植入生物传感，组织工程，伤口愈合，机器人假体，生物燃料电池等，