Self-Assembled DNA/SG-I Nanoflower: Versatile Photocatalytic Biosensors for Disease-Related Markers

DNA nanostructures have recently attracted more attention with functionalities, programmability, and biocompatibility. Herein, a novel self-assembled photocatalytic DNA/SYBR Green I (SG-I) nanoflower (DSNF) was successfully synthesized by rolling circle amplification. DSNF was self-assembled through liquid crystallization of a high concentration of DNA in the RCA products, without relying on the Watson-Crick base-pairing principle. Interestingly, DSNF not only possessed a larger specific surface area and good stability but also exhibited excellent photocatalytic activity that generates singlet oxygen and superoxide anion to oxidate 3,3',5,5'-tetramethylbenzidine. Meanwhile, the photocatalytic DSNF combined with an enzyme-linked immunosorbent assay to develop a new colorimetric sensor for highly specific, sensitive, and visual detection of carcinoembryonic antigens (CEAs). The colorimetric sensor achieved sensitive and low-cost quantitative detection of CEA in the linear range of 0.5-80.0 ng/mL, and the LOD was 0.5 ng/mL. In addition, three negative and seven positive clinical serum samples of CEA were obtained with 100% accuracy using the proposed colorimetric sensor, showing great potential in the clinical application of cancer diagnosis. We envision that this photocatalytic DSNF is expected to provide important perspectives in fluorescence imaging, photosensitizing cancer therapy, and clinical diagnosis fields.