Tetrahedral DNA Framework-Engineered Magnetic Nanozyme for Visual Biomarker Sensing via Alkaline Phosphatase-Triggered Signal Switching

Point-of-care (POC) detection of prostate-specific antigen (PSA) is critical for the early screening and monitoring of prostate cancer (PCa), which facilitates timely intervention and personalized treatment. However, existing POC platforms suffer from inadequate detection sensitivities, susceptibility to matrix interference, and complex sample pretreatment. To address these issues, we proposed a naked-eye and colorimetric sensing platform based on magnetic nanozyme (Fe₃O₄@ZIF-67@Pt) integrated with a tetrahedral DNA framework (TDF) and alkaline phosphatase (ALP)-triggered hydrolysis reaction for PSA detection with superior sensing performances. The as-prepared Fe₃O₄@ZIF-67@Pt nanocomposite synergistically integrates magnetic separation, DNA-conjugated interface engineering, and significantly enhanced peroxidase-like activity, thereby laying the foundation for the construction of high-performance colorimetric biosensors. TDF serves dual functions as a programmable biosensing element, including three vertex anchor ALP reporters for catalytic signal amplification, while the remaining vertex is hybridized with a PSA-specific aptamer to drive competitive target recognition. With the addition of PSA, it preferentially bound to the aptamer, creating a competitive reaction and leading to the release of TDF conjugated to the surface of the magnetic nanozyme. When the ALP-mediated hydrolysis reaction was introduced, the released TDF limited the generation of ascorbic acid (AA) to produce a colorimetric response, resulting in a "signal-on" colorimetric assay. The designed platform allowed for the naked-eye and colorimetric detection of PSA in the range of 0.1-1000 ng/mL, with a detection limit as low as 36 pg/mL, while exhibiting excellent selectivity. Additionally, it achieved a high accuracy and satisfactory reliability for PSA detection in human serum samples as well as successfully distinguished prostate cancer patients from healthy individuals. This work holds great potential for application in the development of a reliable POC platform for biomarker detection.