中文摘要：

以刷子状水溶性共轭聚芴（PFNI）为传感材料,以荧光素标记的核酸适体（FAM-apt15）为探针,设计了一种检测凝血酶的高灵敏度蛋白质传感器.PFNI的刷状结构带有大量正电荷,与负电荷的柔性单链核酸探针形成静电复合物,使能量供体（PFNI）与受体（FAM）之间的距离较近,发生高效荧光共振能量转移（F？ster resonance energy transfer,FRET）.当探针与靶凝血酶结合时,形成刚性且体积较大的G-四链体/凝血酶复合物,由于体积位阻和密集的刷子的阻碍作用,PFNI与FAM之间的距离被拉大,FRET效率显著降低.对缓冲溶液中凝血酶检测的最低检测限可达0.05 nmol/L.与基于线型共轭聚合物的蛋白质检测方法相比,灵敏度提高了至少一个数量级.

英文摘要：

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 fluorescent quantum yield. They have been widely used as an energy donor to amplify fluorescence signal via high efficient F？ster 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 increased significantly, leading to an inefficient FRET process and a low FRET signal. The strategy exhibits excellent specificity 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 polymers, the sensitivity was improved by one order of magnitude. In addition, our strategy also shows the merits of simple, label-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 o