A DNA nanopillar as a scaffold to regulate the ratio and distance of mimic enzymes for an efficient cascade catalytic platform.

Herein, a rigid 3D DNA nanopillar was used to investigate the influence of spatial organization on the cascade activity in multienzyme systems, realizing controllable regulation of the mimic enzyme ratio and spacing for acquiring a high-efficiency enzyme cascade catalytic platform. Initially, the ratio of mimic enzyme AuNPs (glucose oxidase-like activity) and hemin/G-quadruplex DNAzyme (peroxidase-like activity) fixed at the designed position was adjusted by changing the number of edges in a DNA polyhedron, resulting in an optimal mimic enzyme ratio of 1 : 4 with a quadrangular prism as the scaffold. Notably, the DNA nanopillar formed by quadrangular prism layer-by-layer assembly acted as a track for directional and controllable movement of a bipedal DNA walker based on the toehold mediated strand displacement reaction (TSDR), which endowed the assay system with continuous enzyme spacing regulation compared with previous enzyme cascade systems that induced inflexible operation.

PtNPs as Scaffolds to Regulate Interenzyme Distance for Construction of Efficient Enzyme Cascade Amplification for Ultrasensitive Electrochemical Detection of MMP-2.

The high catalytic efficiency of enzyme cascade reaction mainly depends on optimal interenzyme distance regulated by the special scaffolds. In this work, the rigid PtNPs with different sizes were employed as scaffolds to regulate interenzyme distance for efficient enzyme cascade amplification to construct electrochemical biosensor for sensitive detection of matrix metalloproteinases-2 (MMP-2), which overcame the drawbacks of instable construction and sophisticated preparation induced by conventional scaffolds such as metal-organic frameworks (MOFs), DNA nanostructures. Here, cucurbit[7]uril functionalized PtNPs (CB[7]@PtNPs) was utilized to load ferrocene (Fc)-labeled horseradish peroxidase (HRP) and glucose oxidase (GOx) via host-guest interaction between Fc and CB[7], respectively, resulting in the formation of a stable three-dimensional netlike structure containing amounts of enzymes.

DNA Enzyme-Decorated DNA Nanoladders as Enhancer for Peptide Cleavage-Based Electrochemical Biosensor.

Herein, we developed a label-free electrochemical biosensor for sensitive detection of matrix metalloproteinase-7 (MMP-7) based on DNA enzyme-decorated DNA nanoladders as enhancer. A peptide and single-stranded DNA S1-modified platinum nanoparticles (P1-PtNPs-S1), which served as recognition nanoprobes, were first immobilized on electrode. When target MMP-7 specifically recognized and cleaved the peptide, the PtNPs-S1 bioconjugates were successfully released from electrode.