The construction of yolk-shell CuO-Co₃O₄@Co₃O₄ with high carrier separation efficiency and apply for sensitive...

MicroRNA (miRNA) is an endogenously expressed non-coding RNA, and the sensitive monitoring of low-abundance miRNAs holds significant importance for early therapeutic intervention in cancer. Consequently, developing a simple yet highly sensitive miRNA-21 detection method is of substantial importance. This study employs a new Y-shaped DNA-facilitated photoelectrochemical (PEC) sensing interface constructed on a yolk-shell CuO-Co₃O₄@Co₃O₄ photocathode, supplemented by a gold nanoparticle-assisted dissolved oxygen cycle for detecting miRNA-21. A yolk-shell CuO-Co₃O₄@Co₃O₄ nanocomposite was prepared by encapsulating CuO-Co₃O₄ within hollow Co₃O₄ nanocubes, whose unique structure causing an elevate increased specific surface area. Firstly, due to the bandgap matching between Co₃O₄ and CuO, a type II heterojunction formed in the yolk region with an intrinsic electric field, enabling higher carrier separation efficiency. Under xenon lamp illumination, the photocurrent intensity of the CuO-Co₃O₄@Co₃O₄ electrode surpasses that of standalone Co₃O₄ and CuO electrodes. Furthermore, catalytic hairpin assembly driven by miRNA-21 promotes the generation of Y-shaped DNA structures embedded with gold nanoparticles. Gold nanoparticle-assisted dissolved oxygen cycling amplified the detection signal, allowing for ultra-sensitive determination of miRNA-21. The photocurrent response is positively correlated with the number of gold nanoparticles anchored on the electrode surface. This biosensor exhibits favourable linearity and selectivity for the detection of miRNA-21, and the detection limit is 47.464 fM, demonstrating excellent stability and sensitivity. The constructed PEC biosensor holds practical application worth for the early diagnosis and management of miRNA-21 associated disorders.