Water-soluble conjugated polymers (WCPs) composed of a hydrophobic polythiophene main chain with hydrophilic tertiary amine side-chains can directly self-assemble into sphere-like nano-objects in an aqueous solution due to phase separation between the hydrophilic and hydrophobic segments of the polymeric structure. Due to the presence of gas-responsive tertiary amine moieties in the spherical structure, the resulting polymers rapidly and reversibly tune their structural features, surface charge, and fluorescence performance in response to alternating carbon dioxide (CO₂) and nitrogen (N₂) bubbling, which leads to significantly enhanced fluorescence and surface charge switching properties and a stable cycle of on and off switching response. In vitro studies confirmed that the CO₂-treated polymers exhibited extremely low cytotoxicity and enhanced cellular uptake ability in normal and tumor cells, and thus possess significantly improved fluorescence stability, distribution, and endocytic uptake efficiency within cellular organisms compared to the pristine polymer. More importantly, in vivo assays demonstrated that the CO₂-treated polymers displayed excellent biocompatibility and high fluorescence enhancement in living zebrafish, whereas the fluorescence intensity and stability of zebrafish incubated with the pristine polymer decreased linearly over time. Thus, these CO₂ and N₂-responsive WCPs could potentially be applied as multifunctional fluorescent probes for in vivo biological imaging.

中文翻译：

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用于体外和体内生物成像的CO ₂响应型水溶性共轭聚合物

由疏水性聚噻吩主链和亲水性叔胺侧链组成的水溶性共轭聚合物（WCP）可以直接在水溶液中自组装成球形纳米物体，这是由于亲水性和疏水性链段之间的相分离所致。聚合物结构。由于球形结构中存在气体响应性叔胺基团，所产生的聚合物响应于交替的二氧化碳（CO ₂）和氮（N ₂）鼓泡而快速可逆地调节其结构特征，表面电荷和荧光性能，从而显着增强了荧光和表面电荷的开关性能，并实现了稳定的开关响应周期。体外研究证实，CO ₂处理的聚合物在正常细胞和肿瘤细胞中表现出极低的细胞毒性和增强的细胞摄取能力，因此与原始聚合物相比，在细胞生物体内具有显着改善的荧光稳定性，分布和内吞摄取效率。更重要的是，体内试验表明，经CO ₂处理的聚合物在活斑马鱼中表现出出色的生物相容性和高荧光增强，而与原始聚合物一起孵育的斑马鱼的荧光强度和稳定性随时间线性下降。因此，这些CO ₂和N ₂反应灵敏的WCP可能会用作体内生物成像的多功能荧光探针。