Bioinspired Quantum-Guided Engineering of Activatable Probes via Intermolecular Electron Transfer for Single-Cell Molecular Diagnosis

Fluorescence imaging holds theoretical sensitivity for single-cell molecular diagnosis, yet practical performance is limited by residual probe-intrinsic fluorescence arising from incomplete control of intramolecular electron transfer within the probe scaffold. Inspired by natural photosynthesis, where spatially organized pigments enable quantum-coherent excitation transport and precise intermolecular electron transfer, we develop a bioinspired quantum chemistry-guided engineering (BQCE) strategy that programs intermolecular electron transfer to construct molecular assembly based background-eliminating activatable molecule probes (BEAMs). Guided by BQCE, the peroxynitrite-responsive hemicyanine-based BEAM1, despite the intrinsically difficult-to-quench nature of this fluorophore scaffold, achieves near-zero background fluorescence, 103.5-fold activation, and an unprecedented detection limit of 1.3 nM. BEAM1 resolves basal ONOO– fluxes at single-cell resolution, enabling single-cell molecular diagnosis that distinguishes malignant from normal cells based solely on endogenous redox signatures. In vivo, BEAM1 enables detection of lymph nodes containing sparsely distributed metastatic cells, with subsequent ex vivo histological analysis identifying metastatic deposits as small as ∼ 35 μm, extending fluorescence imaging into the regime of single-cell level early cancer detection.