Smartphone-integrated tri-mode RCA-CRISPR/Cas12a biosensor with Fe3O4@Au nanozyme for on-site detection of sugarcane smut at attomolar level.

The devastating sugarcane smut causes up to 70 % sugar yield loss and secondary infections, but field-deployable diagnostics remain challenging due to the limitations of lab-dependent methods. Herein, we report a portable CRISPR/Cas12a-powered biosensor integrated with tri-functional Fe3O4@Au nanozymes and triple-modal signal readout for precise and on-site pathogen detection. By synergizing rolling circle amplification (RCA) with CRISPR/Cas12a trans-cleavage activity, the system achieves ultrasensitive target recognition (detection limit: 32.11 aM for electrochemical mode). The Fe3O4@Au@GOD bioconjugates simultaneously enables magnetic separation, optimizes GOD-mediated colorimetric signals (visual LOD: 49.28 fM), and enhances photothermal responses (LOD: 42.17 fM) via precise biocatalyst-catalyzed TMB oxidation. A smartphone-coupled 3D-printed device integrates electrochemical, colorimetric, and photothermal detection modes, providing cross-validated results that eliminate false positives in complex matrices (recovery: 98-104 %). This field-portable platform completes detection within 2.5-4.5 h (80 % cost reduction vs. qPCR) and demonstrates high specificity against non-target pathogens. The fusion of nanozyme engineering, CRISPR amplification, and multi-modal sensing offers a transformative tool for precision agriculture.