Subcellular distribution-based reference-free cancer cell discrimination with a novel AIE cationic probe.

BACKGROUND: The development of specific fluorescent probes for cancer cell discrimination holds significant promise for advancing cancer diagnostics. Conventionally, these probes operate by translating differences in biomarkers or microenvironmental factors into variations in whole-cell fluorescence intensity. However, this dominant, intensity-based strategy is highly susceptible to extraneous fluctuations arising from probe concentration, illumination instability and complex intracellular environment. Consequently, these methods suffer from compromised reliability, critically necessitating reference controls for accurate analysis. This limitation underscores the urgent need for new analytical modalities that can achieve robust cell discrimination without relying on intensity measurements.

RESULT: We report TPC-CD, a novel cationic probe featuring a D-π-A structure. It exhibits excellent photophysical properties, including distinct Aggregation-Induced Emission (AIE) characteristics, near-infrared emission, and a large Stokes shift. Its design leverages a finely tuned balance of charge and lipophilicity to specifically target the higher negative charge density characteristic of cancer cell membranes. This charge-dependent mechanism was rigorously validated: reducing the membrane's negative charge (via valinomycin or l-polylysine) triggered probe internalization, confirming its subcellular distribution directly reports the cell's surface charge state. Consequently, TPC-CD provides robust and reliable visual discrimination across a series of cell lines, selectively accumulating on the membranes of cancer cells via strong electrostatic interactions, while readily penetrating into the cytoplasm of normal cells, resulting in a diffuse intracellular signal.

SIGNIFICANCE: The developed subcellular distribution-based strategy represents a paradigm shift from conventional methods. By operating independently of fluorescence intensity, it inherently circumvents analytical errors and false positives caused by extraneous fluctuations, establishing a robust, reference-free modality for cancer cell discrimination. This work not only presents a powerful new tool but also offers a novel design principle for creating next-generation smart probes for fluorescence imaging and analysis.