Ultrasensitive photoelectrochemical platform based on high-efficient photoactive AuNPs@Bi2S3/Bi2O3 nanocomposite for detection of microRNA-21

Herein, a novel [email protected]2S3/Bi2O3 nanocomposite as photoactive material was employed to construct ultrasensitive photoelectrochemical (PEC) sensing platform for microRNA-21 (miRNA-21) assay. Firstly, the Bi2S3/Bi2O3 with well-matched energy levels was prepared. Since the band gap of Bi2O3 was wide enough, the concentration of carriers could be sufficiently ensured to obtain an intense photocurrent response. Then, the formation of [email protected]2S3/Bi2O3 obtained an eight-fold higher photocurrent signal than that of Bi2S3/Bi2O3, which was due to the surface plasmon resonance (SPR) effect of AuNPs providing more photoelectrons, thereby enhancing the photoelectric conversion efficiency from Bi2S3/Bi2O3 to [email protected]2S3/Bi2O3. Additionally, with the assistant of catalytic hairpin assembly (CHA) and Nt.BsmAI enzyme-assisted amplification strategy, abundant double-stranded DNA (dsDNA) was generated to load the mimic enzyme manganese porphyrin (MnPP), which allowed 4-chloro-1-naphthol (4-CN) to be catalyzed to benzo-4-chlorohexadienone (4-CD) precipitate in the presence of H2O2. The developed biosensor for the detection of miRNA-21 exhibited an ideal linear relationship by diminishing the photocurrent response ranging from 100 aM to 10 nM with a lower detection limit of 34 aM. Importantly, this proposed strategy provided a versatile nanocomposite [email protected]2S3/Bi2O3 that could be applied to construct ultrasensitive PEC biosensors for bioanalysis and disease diagnosis.