Simple and sensitive detection of proteins is crucial in biological analysis and medical diagnosis. Conjugated polymers (CPs) with π-conjugated backbones were recognized as having excellent light-harvesting capability and high fluo- rescent quantum yield. They have been widely used as an energy donor to amplify fluorescence signal via high efficient Foster resonance energy transfer (FRET). In particular, conjugated polymer brush with high charge density provides more possibilities due to stronger electrostatic interactions with negatively charged biomolecules. Here, we developed a highly sensitive protein biosensor for thrombin detection based on a conjugated polymer brush (PFNI) and a fluorescein-labeled aptamer (FAM-apt15). PFNI is a water-soluble cationic polyfluorene derivate with extremely high charge density (78 positive charges per repeat unit). PFNI can attract negatively charged aptamer through strong electrostatic interactions. In this case, the energy donor (PFNI) and acceptor (FAM) are in a close proximity, which results in an efficient FRET process and a high FRET signal. However, when the FAM-apt15 combines with the target protein, a rigid and big-sized G-quadruplex/thrombin complex formed. Due to the steric hindrance from the densely brush of PFNI, the distance between the two fluorophores in- creased significantly, leading to an inefficient FRET process and a low FRET signal. The strategy exhibits excellent specific- ity and the limit of detection (LOD) for thrombin in buffer was estimated to be 0.05 nmol/L. It also works well in diluted serum and a LOD of 0.2 nmol/L can be obtained. Compared to the biosensors based on traditional linear conjugated poly- mers, the sensitivity was improved by one order of magnitude. In addition, our strategy also shows the merits of simple, la- bel-free, and low-cost because labeled DNA is much more expensive than unlabeled one. Based on the specific binding of aptamer and protein, this novel method can be extended to a highly sensitive detection of more proteins. Keywords conjugated polymer; aptamer; Foster resonance energy transfer; thrombin; biosensor

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基于共轭聚合物刷的高灵敏度蛋白质生物传感器

简单而灵敏的蛋白质检测在生物分析和医学诊断中至关重要。具有π共轭骨架的共轭聚合物（CP）被认为具有优异的光捕获能力和高荧光量子产率。它们已被广泛用作能量供体，通过高效的福斯特共振能量转移 (FRET) 放大荧光信号。特别是，由于与带负电荷的生物分子的更强静电相互作用，具有高电荷密度的共轭聚合物刷提供了更多的可能性。在这里，我们开发了一种基于共轭聚合物刷 (PFNI) 和荧光素标记适体 (FAM-apt15) 的高灵敏度蛋白质生物传感器，用于凝血酶检测。PFNI 是一种水溶性阳离子聚芴衍生物，具有极高的电荷密度（每个重复单元 78 个正电荷）。PFNI 可以通过强静电相互作用吸引带负电的适体。在这种情况下，能量供体 (PFNI) 和受体 (FAM) 非常接近，从而导致高效的 FRET 过程和高 FRET 信号。然而，当 FAM-apt15 与目标蛋白结合时，就会形成一个刚性的大尺寸 G-四链体/凝血酶复合物。由于 PFNI 密集刷的空间位阻，两个荧光团之间的距离显着增加，导致 FRET 过程效率低下和 FRET 信号低。该策略表现出出色的特异性，缓冲液中凝血酶的检测限 (LOD) 估计为 0.05 nmol/L。它也适用于稀释的血清，可获得 0.2 nmol/L 的 LOD。与基于传统线性共轭聚合物的生物传感器相比，灵敏度提高了一个数量级。此外，我们的策略还展示了简单、无标签和低成本的优点，因为标记的 DNA 比未标记的 DNA 贵得多。基于适体和蛋白质的特异性结合，这种新方法可以扩展到对更多蛋白质的高灵敏度检测。关键词共轭聚合物；适体；促进共振能量转移；凝血酶; 生物传感器 并且成本低，因为标记的 DNA 比未标记的 DNA 贵得多。基于适体和蛋白质的特异性结合，这种新方法可以扩展到对更多蛋白质的高灵敏度检测。关键词共轭聚合物；适体；促进共振能量转移；凝血酶; 生物传感器 并且成本低，因为标记的 DNA 比未标记的 DNA 贵得多。基于适体和蛋白质的特异性结合，这种新方法可以扩展到对更多蛋白质的高灵敏度检测。关键词共轭聚合物；适体；促进共振能量转移；凝血酶; 生物传感器