Novel electrochemical nanoswitch biosensor based on self-assembled pH-sensitive continuous circular DNA.

Area of Science:

• Biotechnology
• Biosensing
• Nanotechnology

Background:

• Nucleic acid nanoswitches offer excellent biocompatibility and design flexibility for biosensing applications.
• Developing sensitive and specific detection methods for microRNAs (miRNAs) is crucial for early disease diagnosis.

Purpose of the Study:

• To construct a novel electrochemical platform for microRNA-21 (miRNA-21) detection using a self-assembled, pH-sensitive DNA nanoswitch.
• To investigate the pH-dependent activation mechanism of the DNA nanoswitch for enhanced biosensing performance.

Main Methods:

• Designed and synthesized inside ring probes (IRPs) and outside ring probes (ORPs) that self-assemble into a continuous circular DNA structure at pH 6.
• Utilized the self-assembled circular DNA structure to capture a large amount of ruthenium hexacyanide (RuHex) as an electrochemical signal indicator.
• Developed an electrochemical detection strategy triggered by the pH-sensitive self-assembly of the DNA nanoswitch.

Main Results:

• The DNA nanoswitch demonstrated pH sensitivity, activating only at pH 6 to form a continuous annular DNA structure.
• Achieved highly sensitive detection of miRNA-21 within a concentration range of 10⁻¹⁵ to 10⁻⁸ M.
• Established a low limit of detection for miRNA-21 at 0.84 fM.
• Successfully detected miRNA-21 directly in human serum samples without prior pretreatment.

Conclusions:

• The proposed electrochemical DNA nanoswitch provides a sensitive and specific platform for miRNA-21 detection.
• The pH-sensitive activation mechanism offers a novel approach for biosensor design and control.
• This biosensor shows significant potential for biomarker detection and clinical diagnosis, particularly in analyzing complex biological samples like serum.