Amplified Assembly of a Multifunctional 3D DNA Nanomachine for Electrochemical and Colorimetric Dual-Mode Assays

DNA nanomachines have been widely applied in biosensing; however, further enhancing their signal amplification capability and assay reliability remains a major challenge. Herein, a novel strategy was proposed to construct a multifunctional three-dimensional DNA nanomachine for the development of an electrochemical and colorimetric dual-mode biosensing method for detecting the estrogen pollutant 17β-estradiol. Aptamer recognition-triggered catalytic hairpin assembly, together with a cascade Nb.BbvCI-assisted DNA polymerization reaction, drove the amplified assembly of the DNA nanomachine composed of multiple triangular prism units. The abundant Mg 2+ -dependent DNAzymes formed on the nanomachine enabled its efficient walking on an iron-based metal–organic framework (Fe-MOF)-modified electrode, thereby generating an electrochemical signal. Meanwhile, numerous G-quadruplexes were formed accompanying the DNA nanomachine assembly, thereby enabling sensitive colorimetric signal readout through the excellent peroxidase-mimicking activity of the formed G-quadruplex/hemin DNAzymes, synergistically promoted by released Fe-MOFs. Consequently, the proposed method exhibited wide linear ranges of 0.01 pg mL –1 to 1 ng mL –1 (electrochemical) and 0.1 pg mL –1 to 10 ng mL –1 (colorimetric) with detection limits as low as 3.9 fg mL –1 and 10.5 fg mL –1, respectively. In addition, the method showed simple operation, excellent repeatability, and enhanced reliability through cross-validation between the dual detection modes. Therefore, this work provides a robust and sensitive approach for monitoring environmental estrogen pollutants.