Dissolved oxygen in cell culture media represents an interesting parameter worth monitoring, especially at very low concentrations. Indeed, cells grow faster and live longer in hypoxic conditions, and recent studies relate stronger tumor malignancy, recurrence, and progression with reduced oxygen levels. Standard techniques for dissolved oxygen evaluation rely either on optical investigations or on electrochemical methods. The former requires complex protocols and expensive instrumentations, while for the latter, the presence of a silver/silver chloride electrode hinders the device miniaturization and induces cytotoxic effects. In this work, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (Pedot:Pss)-based Organic Electrochemical Transistors (OECTs) are presented as dissolved oxygen sensors. The catalytic activity of the Pedot chains is exploited for the transduction since oxygen reduction reactions, occurring at the polymer/electrolyte interface, induce Pedot:Pss to switch from the less conductive neutral state (off) to the more conductive oxidized one (on). This transient-doping effect enhances OECT current output, which presents a high signal to noise ratio (i.e., >102–103). The transistor architecture allows for high output/input signal power amplification (i.e., >15 dB–22 dB) and excellent sensitivities [328 ± 11 mV/dec and −0.38 ± 0.02 mA/dec for transfer and Ids(t), respectively], together with a low detection limit (0.9 µM, which represents the 0.07% of oxygen partial pressure). Finally, the here reported OECT sensors are demonstrated to work also in a real-life complex biological environment. This work paves the way for reliable, real-time oxygen monitoring in in vitro cell cultures for various relevant applications, such as investigating the influence of hypoxia conditions on cell lines or tumors.

中文翻译：

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在电流增强模式下工作的瞬态掺杂有机电化学晶体管作为溶解在溶液中的低浓度氧的传感装置

细胞培养基中的溶解氧是一个值得监测的有趣参数，尤其是在非常低的浓度下。事实上，细胞在缺氧条件下生长更快，寿命更长，最近的研究将更强的肿瘤恶性、复发和进展与氧水平降低联系起来。溶解氧评估的标准技术依赖于光学研究或电化学方法。前者需要复杂的协议和昂贵的仪器，而对于后者，银/氯化银电极的存在阻碍了设备的小型化并引起细胞毒性作用。在这项工作中，基于聚（3,4-亚乙基二氧噻吩）：聚（苯乙烯磺酸）（Pedot：Pss）的有机电化学晶体管（OECT）被用作溶解氧传感器。Pedot 链的催化活性被用于转换，因为发生在聚合物/电解质界面的氧还原反应诱导 Pedot:Pss 从导电性较差的中性状态（关闭）切换到导电性更高的氧化状态（开启）。这种瞬态掺杂效应增强了 OECT 电流输出，呈现高信噪比（即 >102–103）。晶体管架构允许高输出/输入信号功率放大（即 >15 dB–22 dB）和出色的灵敏度 [传输和 Ids(t) 分别为 328 ± 11 mV/dec 和 -0.38 ± 0.02 mA/dec] ，以及低检测限（0.9 µM，代表氧分压的 0.07%）。最后，这里报道的 OECT 传感器被证明也可以在现实生活中的复杂生物环境中工作。