Autocatalytic replicated Mg2+-ligation DNAzyme as robust biocatalyst for sensitive, label-free and enzyme-free electrochemical biosensing of protein

Publication date: Available online 12 February 2020Source: Sensors and Actuators B: ChemicalAuthor(s): Yumeng Liao, Shijing Guo, Xiaoyu Hua, Ruo Yuan, Wenju XuAbstractHerein, an enzyme- and label-free electrochemical aptasensor was developed for the amplified detection of protein (mucin 1, MUC1 as tested model) by utilizing autocatalytic and catabolic Mg2+-ligation DNAzyme as robust biocatalyst. The MUC1-affinity aptamer sequence is encoded in DNA hairpin 1 (HP1). The combined product of HP1 with MUC1 triggers the formation of active Mg2+-dependent DNAzyme in the presence of sequence-specific ssDNA (S1) and hairpin 2 (HP2) that especially consists of S1 and the other ssDNA (S2). When introducing Mg2+, HP2 as the substrate strand of this DNAzyme is cleaved at Mg2+-recognizable site, releasing S1 to repeatedly activate the autonomous replication and catabolism of new DNAzyme units. As a result, the multiple liberated S2 was further incubated in the modified electrode surface to unfold C-rich hairpin 3 (HP3) at neutral pH. While the formed duplex with negative charges is dehybridized due to the configuration switch of unfolded HP3 into positively charged i-motifs at decreased pH, leading to enhanced electrostatic attraction to redox pairs [Fe(CN)6]3-/4- and accelerated electron transfer in the electrode surface. Thus, the Faraday impedance (Ret) significantly decreased with MUC1-responsive variations for the electrochemical quantification of MUC1 in the range of 10 fg·mL-1 to...

Source: Sensors and Actuators B: Chemical - February 14, 2020 Category: Chemistry Source Type: research