CRISPR-Driven Portable Piezoresistive Biosensor with Cascaded Signal Amplification for Ultrasensitive Osteocalcin Detection

Low-turnover osteoporosis diagnosis urgently requires sensitive detection of low-abundance osteocalcin (OC), yet conventional methods remain constrained by insufficient sensitivity, cumbersome instrumentation, and laborious operations. We devise a CRISPR-driven pressure bioassay that synergistically integrates molecular recognition, enzymatic amplification, and signal transduction for dual-amplification-enhanced OC quantification. The system features an engineered "locked-to-activated" molecular switch, where target binding liberates CRISPR-activating DNA strands, initiating Cas14a-catalyzed cleavage of ssDNA tethers on Fe₃O₄-ssDNA-Pt nanoassemblies. This cascade releases a multitude of platinum nanoparticles (the first amplification stage). Subsequently, the liberated platinum nanoparticles drive the catalytic decomposition of H₂O₂ within sealed microchambers, generating a massive flux of oxygen gas molecules (O₂) (second amplification stage). Coupled with a laboratory-fabricated nanostructured piezoresistive sensor (20 Pa resolution), this two-stage amplification strategy achieves high sensitivity with a 7.31 pg/mL detection limit, 124-fold lower than commercial ELISA, while completing analysis within 60 min. The platform demonstrates remarkable specificity (spike recovery of 113%, 112%, and 110% in human serum), operational robustness across varying environmental temperatures (15-40 °C), and compatibility with miniaturized instrumentation. Clinical validation through serum matrix analysis reveals excellent correlation (R² = 0.982) with reference values. By integrating CRISPR programmability, nanozyme-amplified signaling, and portable piezoresistive sensing, this work provides a sensitive point-of-care osteoporosis screening method for resource-limited settings.