Split-type photoelectrochemical biosensing for miRNA-144 assay based on a ZnIn₂S₄/TiO₂ heterojunction

Highly efficient photoelectroactive materials with simple synthesis are essential for photoelectrochemical (PEC) biosensing. This study reports a facile hydrothermal synthesis of ZnIn₂S₄/TiO₂ type II heterojunctions on FTO, creating a robust sensing platform. The favorable band energy alignment between ZnIn₂S₄ and TiO₂ enhances charge transfer and charge carrier separation under illumination, resulting in a 24-fold photocurrent increase compared to TiO₂. By combining magnetic separation with hybridization chain reaction (HCR) signal amplification, a highly sensitive split-type biosensor for miRNA-144 was developed. The resulting biosensor demonstrated a linear detection range from 10 fM to 1 nM, with a limit of detection (LOD) of 6.75 fM. Furthermore, excellent selectivity, long-term stability, and reliable miRNA-144 detection in spiked human serum samples were demonstrated, highlighting the great potential of this PEC biosensor for clinical miRNA applications.