Resolving the Sensitivity-Specificity Trade-Off in Fluorescent Probes via a Tandem-Activatable Shielding Strategy

For precise tumor diagnosis, the intrinsic trade-off between sensitivity and specificity in fluorescent probes remains a longstanding bottleneck, underscoring an urgent need for strategies to break this fundamental constraint. To address the specificity limitation, we exploited a highly polarity-sensitive fluorescent scaffold to construct a tandem-activatable probe, enabling sequential activation by the acidic tumor microenvironment and the angiogenic marker aminopeptidase N. Whereas the single-locked counterpart is prone to premature activation in circulation, the tandem-locked probe remains inactive owing to a maleamic acid-based shielding unit and is activated only upon encountering these two tumor hallmarks. Furthermore, this shielding strategy increases probe hydrophobicity, enhancing tumor uptake and driving accumulation of released fluorophores in low-polarity lipid droplets, where fluorescence is markedly amplified to improve imaging sensitivity. The probe exhibits rapid and specific activation across various solid tumors with minimal toxicity, thus effectively resolving the sensitivity-specificity trade-off in probe design for in vivo applications.