Assembly-formed bioorthogonal chimeric artificial receptors enable high-contrast fluorescence imaging of tumors.

Conventional receptor-targeted fluorescent probes have shown promise in tumor imaging, yet achieving a high tumor-to-normal (T/N) tissue ratio in vivo remains challenging due to limited biomarker density on tumor cell membranes. Here, we present an in situ assembly strategy of bioorthogonal-functionalized chimeric artificial receptors (BCARs) that locally constructs BCARs on tumor surfaces, which amplify fluorescence signals and enable high-contrast imaging. Rapid, selective membrane engineering under physiological conditions increases effective receptor density, enhancing fluorophore binding and tumor visualization. Mechanistic studies reveal that BCARs exhibit exceptional membrane retention and spatial precision, sustaining signal amplification in heterogeneous tumor microenvironments. In air-pouch and orthotopic bladder cancer models, BCARs notably improve the T/N imaging ratio and tumor boundary delineation. Translational validation with surgical specimens from 14 patients with bladder cancer confirms clinical feasibility. This work establishes a versatile platform for on-site receptor reprogramming and signal amplification, offering a powerful tool for high-contrast tumor margin detection.