基于级联立足点介导链置换用于非酶靶标循环放大电化学检测SARS-CoV-2

Cascaded strand displacement for non-enzymatic target recycling amplification electrochemical detection of SARS-CoV-2

基于2个级联立足点介导DNA链置换反应(TSDRs),构建电化学生物传感器实现对SARS-CoV-2靶标核酸的低成本、灵敏及强特异性检测。在热力学熵的驱动下,靶标核酸与电极上双链DNA(dsDNA)固定探针上的第1个立足点(Toehold)区域结合引发第1个TSDR,并露出第2个Toehold区域。亚甲基蓝修饰的信号探针触发第2个TSDR,使得靶标核酸被循环利用。基于级联TSDRs,传感器表面结合大量信号探针产生明显增强的方波伏安(SWV)电化学信号。结果表明,SWV信号强度与靶标核酸浓度的对数成正比,在5×10^(-14)~5×10^(-10)mol/L范围内呈良好的线性关系,检出限为1.8×10^(-14)mol/L。该传感器可用于人血清样本(10%)中SARS-CoV-2靶标核酸的检测。

An electrochemical biosensor for low cost and highly sensitive and selective detection of SARS-CoV-2 target nucleic acid was developed based on two cascaded toehold-mediated strand displacement reactions(TSDRs).Driven by thermodynamic entropy,the target nucleic acid bound to the first toehold region of the probes,leading to the first TSDR and the second toehold region exposed.Subsequently,the methylene blue(MB)-modified signal probe triggered the second TSDR and led to cyclic reuse of the target nucleic acid.Based on cascaded TSDRs,a large number of signal probes were combined on the sensor surface to produce significantly enhanced square wave voltammetry(SWV)electrochemical signals.The results showed that the SWV signal intensity was proportional to the logarithm of the target nucleic acid concentration,and had a good linear relationship in the range of 5×10^(-14)-5×10^(-10)mol/L with a detection limit of 1.8×10^(-14)mol/L.Moreover,the sensor could be employed to monitor SARS-CoV-2 nucleic acid in 10%serum samples.