In Vivo Spatiotemporal Protection and Recognition of Circulating Tumor DNA for Early Cancer Diagnosis and Monitoring

Circulating tumor DNA (ctDNA) offers a promising avenue for noninvasive cancer diagnosis and prognosis, yet its effective utilization is fundamentally limited by rapid in vivo clearance and nuclease-mediated degradation, resulting in extremely low bioavailability. In addition, conventional in vitro recognition-based ctDNA detection means may potentially compromise the diagnostic accuracy. Here, we report an in vivo spatiotemporal protection and recognition strategy that actively enhances ctDNA bioavailability, enabling accurate early cancer diagnosis and quantitative monitoring of disease progression and therapeutic response. This strategy integrates immunoglobulin G-modified liposomes to transiently saturate the mononuclear phagocyte system, thereby suppressing ctDNA clearance, together with systemically administered anti-dsDNA monoclonal antibodies that protect ctDNA from nuclease degradation. The synergistic in vivo intervention enhances recoverable ctDNA levels by up to 56.2-fold relative to unprotected controls. The protected ctDNA subsequently undergoes sequence-specific hybridization with an in vivo recognition nanoprobe, triggering the release and renal excretion of locked nucleic acid (LNA) reporter strands. These urinary LNAs further induce the dissolution of a horseradish peroxidase (HRP)-encapsulated DNA gel to liberate HRP, which generates highly amplified current on a disposable sensor electrode, thereby markedly improving detection sensitivity for noninvasive identification of small tumors down to 30 mm³. This methodology further enables quantitative monitoring of tumor progression and assessment of doxorubicin (DOX)-mediated therapeutic efficacy, underscoring its robust broad potential for convenient and accurate cancer diagnosis and treatment evaluation.