Toward Lab‐In‐Fiber Liquid Biopsy: Graphene‐Oxide Functionalized Anti‐Resonant Optical Fiber for Single‐Device Capture‐Enrichment‐Detection‐Recovery of Circulating Tumor Cells

Metastatic spread in aggressive cancers is often initiated by circulating tumor cells (CTCs) before primary tumor detection. Current CTC analysis faces fundamental limitations due to extreme cell scarcity (≈10 cells mL^-1 blood) and reliance on large sample volumes (>7.5 mL). To address these challenges, an integrated graphene oxide-functionalized hollow-core anti-resonant fiber (HARF-GO) platform is developed that combines: 1) enhanced photon-matter interactions through optical confinement, enabling 700-fold signal amplification compared to microplate assays without requiring external photonic components, and 2) intrinsic microfluidic capabilities for continuous processing of microliter-scale samples. This "lab-in-fiber" system achieves exceptional sensitivity (2 CTCs/assay) using <1 mL serum within 1 h - performance parameters that fully meet clinical CTC analysis requirements. Notably, captured cells maintain 94% viability after gentle elution with high-ionic-strength buffer, enabling robust downstream molecular analysis. By seamlessly integrating cell capture, enrichment, optical detection, and viable cell recovery in a single device, the technology overcomes critical limitations of current liquid biopsy methods, providing new capabilities for both minimal residual disease monitoring and precision oncology applications.