Currently, developing an effective and easy-to-operate signal amplification assay to detect the trace-amount miRNAs in serum remains a significant challenge. Herein, an ultrasensitive CeO₂@Ag hybrid nanoflower (CeO₂@Ag HNF)-labeled electrochemical biosensor was developed for sensing miRNA, based on a target-feedback rolling-cleavage (TFRC) signal amplifier. CeO₂@Ag HNFs possessing a unique three-dimensional layered structure were synthesized without any complex reaction conditions, such as heating and vacuum. The bimetallic nanoflowers provided a large surface area and excellent CAT-like activity, thereby enhancing electrochemical performance. Based on the principle of branched catalytic hairpin assembly, target miRNA could continuously trigger the assembly of branched junctions with ends composed of DNAzyme. The activated DNAzyme was able to cleave the hairpin substrate efficiently and release to capture more CeO₂@Ag HNFs label. The process combining target-driven branched catalytic hairpin assembly and DNAzyme-assisted rolling cleavage were defined as TFRC signal amplification. This sensitive electrochemical biosensor exhibited good linear relationship of 1 fM − 1 nM with a detection limit down to 0.89 fM. The proposed method is expected to have a promising application in the miRNA-associated fundamental research and clinical diagnosis.

目前，开发一种有效且易于操作的信号放大检测方法来检测血清中的微量 miRNA 仍然是一项重大挑战。在此，基于目标反馈滚动切割 (TFRC) 信号放大器，开发了一种超灵敏的 CeO ₂ @Ag 杂化纳米花 (CeO _{2 @Ag HNF) 标记的电化学生物传感器，用于检测 miRNA。}氧化铈₂@Ag HNFs 具有独特的三维层状结构，是在没有任何复杂反应条件（如加热和真空）的情况下合成的。双金属纳米花提供了大的表面积和优异的类 CAT 活性，从而提高了电化学性能。基于分支催化发夹组装的原理，目标miRNA可以连续触发分支连接的组装，末端由DNAzyme组成。活化的 DNAzyme 能够有效地切割发夹底物并释放以捕获更多的 CeO ₂@Ag HNFs 标签。结合目标驱动的分支催化发夹组装和DNAzyme辅助滚动切割的过程被定义为TFRC信号放大。这种灵敏的电化学生物传感器表现出 1 fM - 1 nM 的良好线性关系，检测限低至 0.89 fM。所提出的方法有望在miRNA相关的基础研究和临床诊断中具有广阔的应用前景。