In this study, a simple, economic, and label-free electrochemical biosensor was developed for highly sensitive and selective miR-21 detection based on Fe(CN) 6 3− /Fe(CN) 6 4− electrochemical signal, which relies on DNA structures conjugating with carboxyl multi-wall carbon nanotubes (MWCNTs-COOH)-modified glassy carbon electrode (GCE). High sensitivity and specificity of the biosensor were achieved by taking advantage of the target-recycled non-enzymatic amplification strategy (TRNEAS), which relies on sequence-specific hairpin strand displacement and does not require the addition of environment-susceptible enzymes. Besides, the SP-DNA strictly binds to the cMWCNTs/GCE via amide bonds, which ensure good electrochemical results and excellent stability for target miRNA detection. The developed miR-21 electrochemical biosensor exhibited a broad linear dynamic range of 0.1 fmol to 5 pmol and a detection limit of 56.7 amol for miR-21 detection in vitro . The relative miR-21 expression levels were particularly detected by our developed miR-21 biosensor and were highly consistent with the stem-loop RT-PCR results. In summary, our developed electrochemical biosensor exhibits great potential for further application in biomedical research and early clinical diagnosis.
Constructing precise delivery systems to enhance the antitumor efficacy of drugs represents a pressing clinical practice need. The characteristics of suitable physiological stability, flexible tunable size, and highly programmable architecture make functional DNA scaffolds an ideal solution to this requirement. Here, we designed DNA oligonucleotide probes Y 1 , Y 2 and Y 3 to construct a smart-responsive Y-shaped DNA scaffold drug conjugate (sYDD). This sYDD incorporates two AS1411 aptamers, an apurinic/apyrimidinic (AP) site, a B-cell lymphoma-2 (Bcl-2) antisense oligonucleotide (ASO) and a doxorubicin (DOX)-carrying sequence. The Bcl-2 ASO and DOX within sYDD could be responsively released in tumor cells that exhibited high expression of apurinic/apyrimidinic endonuclease 1 (APE1) and microRNA-21 (miR-21). And the in vitro and in vivo experiments demonstrated that sYDD exhibited substantial antitumor efficiency. Moreover, the flow cytometry and RNA sequencing results proved that the proposed sYDD effectively activated immune responses. This strategy provides an alternative approach for designing synergistic chemo-gene drug conjugates, which facilitates the development of precision tumor treatment modalities.
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