MnO2@Au nanostructures supported colorimetric biosensing with duplex-specific nuclease-assisted DNA structural transition

Manganese dioxide (MnO₂) nanosheets are regarded as a new class of two-dimensional nanomaterials with several attractive properties with enormous progress in biomedical fields. Gold nanoparticles (AuNPs) are also important biocompatible nanomaterials with unusual optical properties. Hetero-nanostructure of MnO₂ and AuNPs with the medium of DNA is an interesting topic. In this work, the protection of the hetero-nanostructure from salt-induced aggregation is systematically investigated including the effects of sequence length, reagents concentrations, incubation time and temperature. The MnO₂@Au nanostructures are thus applied for the analysis of miRNA. Duplex-specific nuclease (DSN) catalyzed digestion, hybridization chain reaction (HCR) and catalytic hairpin assembly (CHA) are utilized for signal amplification. By finally analyzing the optical responses of the nanocomponents, highly sensitive analysis of target miRNA can be achieved. Excellent analytical performances are attributed to the unique features of MnO₂@Au nanostructures and signal amplification designs. They are promising basis for the construction of novel biosensors for clinical applications.

Ti3C2@Bi2O3 nanoaccordion for electrochemical determination of miRNA-21

Based on a dual signal amplification strategy of novel accordion-like Bi₂O₃-decorated Ti₃C₂ (Ti₃C₂@Bi₂O₃) nanocomposites and hybridization chain reaction (HCR), an ultra-sensitive electrochemical biosensor was constructed for miRNA-21 detection. By etching Ti₃AlC₂ with HF, Ti₃C₂ with an accordion-like structure was first obtained and subsequently covered by Bi₂O₃ nanoparticles (NPs), forming Ti₃C₂@Bi₂O₃. A layer of Au NPs was electrodeposited on the glassy carbon electrode coated with Ti₃C₂@Bi₂O₃, which not only significantly improved the electron transport capacity of the electrode but also greatly increased its surface active area. Upon the immobilization of the thiolated capture probe (SH-CP) on the electrode, the target miRNA-21 specifically hybridized with SH-CP and thus opened its hairpin structure, triggering HCR to form a long double strand with the primers H1 and H2. A large number of the electrochemical indicator molecules were thus embedded inside the long double strands to produce the desirable electrochemical signal at a potential of - 0.19 V (vs. Ag/AgCl). Such dual signal amplification strategy successfully endowed the biosensor with ultra-high sensitivity for miRNA-21 detection in a wide linear range from 1 fM to 100 pM with a detection limit as low as 0.16 fM. The excellent detection of miRNA-21 in human blood plasma displayed a broad prospect in clinical diagnosis. An ultra-sensitive electrochemical biosensor was successfully constructed for miRNA-21 detection in human blood plasma based on the dual signal amplification strategy of novel accordion-like Bi₂O₃ decorated Ti₃C₂ (Ti₃C₂@Bi₂O₃) nanocomposites and hybridization chain reaction.

Nucleic acid isothermal amplification-based soft nanoarchitectonics as an emerging electrochemical biosensing platform

The emergence of nucleic acid isothermal amplification strategies based on soft nanoarchitectonics offers a new dimension to the traditional electrochemical technique, particularly because of its flexibility, high efficiency, and increased sensitivity for analytical applications. Various DNA/RNA isothermal amplification strategies have been developed for the design and fabrication of new electrochemical biosensors for efficient and important biomolecular detection. Herein, we provide an overview of recent efforts in this research field and the strategies for signal-amplified sensing systems, with their biological applications, current challenges and prospects in this promising new area.