Ultrasensitive Detection of Circular RNA via Rolling Circle Amplification-Coupled Surface-Enhanced Raman Scattering for Early Breast Cancer Diagnosis

@bio-DNA@SERS tag substrate with reverse transcription-rolling circle amplification (RT-RCA) and duplex-specific nuclease (DSN)-driven signal amplification, enabling attomolar-level quantification of hsa_circ_0067842 in serum. This assay achieved detection limits of 75.86 aM in buffer and 1.23 aM in serum, while maintaining exceptional selectivity against homologous linear RNAs. Clinical evaluation demonstrated that the SERS detection system (SERSDS) accurately discriminated breast cancer patients from healthy controls, yielding an AUC of 0.978, a sensitivity of 98%, and a specificity of 96%. Furthermore, dual-target analysis combining hsa_circ_0067842 with hsa_circ_0000512 significantly improved differentiation between benign and malignant breast nodules (AUC = 0.992), outperforming conventional tumor biomarkers. Collectively, this SERS-based sensor exhibited outstanding sensitivity, reproducibility, and operational stability, offering a promising avenue for early, accurate, and minimally invasive diagnosis and molecular classification of breast cancer.