Ti 3 C 2 @Bi 2 O 3 nanoaccordion for electrochemical determination of miRNA-21.

Based on a dual signal amplification strategy of novel accordion-like Bi 2 O 3 -decorated Ti 3 C 2 (Ti 3 C 2 @Bi 2 O 3 ) nanocomposites and hybridization chain reaction (HCR), an ultra-sensitive electrochemical biosensor was constructed for miRNA-21 detection. By etching Ti 3 AlC 2 with HF, Ti 3 C 2 with an accordion-like structure was first obtained and subsequently covered by Bi 2 O 3 nanoparticles (NPs), forming Ti 3 C 2 @Bi 2 O 3 . A layer of Au NPs was electrodeposited on the glassy carbon electrode coated with Ti 3 C 2 @Bi 2 O 3 , 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 Bi 2 O 3 decorated Ti 3 C 2 (Ti 3 C 2 @Bi 2 O 3 ) nanocomposites and hybridization chain reaction.