“Zero-On” NIR-II Photoacoustic Organic Nanoprobes for Ultra-Accurate Companion Diagnostics of Cancer Immunotherapy Response

> 0.05 vs water), eliminating probe background interference after intratumoral accumulation and ensuring detected signals in the tumor exclusively from true biomarker activation. In vivo, SPCDx accurately distinguishes immune drugs of varying efficacy and identifies low-efficacy immune response mice with 100% accuracy in a blind study, outperforming conventional "off-on" probes (56.3%). SPCDx further accurately detects early immune responses >42 h before clinical-standard flow cytometry biopsies and 6 days before observable tumor shrinkage. Our "zero-on" concept offers a molecular blueprint for ultra-accurate CDx of cancer immunotherapy response.