Viscosity-Responsive Cell-Membrane-Anchored Fluorescent Probe for Visualization of Tumor Cell Membranes and Tumors

Probing the viscosity changes in the tumor cell membrane microenvironment is of great significance for gaining a deeper understanding of the physiological mechanisms of cell carcinogenesis. In this paper, a cell-membrane-anchored fluorescent probe (M1) for monitoring viscosity was designed by constructing a rhodamine-based amphiphilic structure with a hydrophilic sulfonate moiety. Probe M1 exhibited a selective and sensitive fluorescence response toward viscosity in the near-infrared (NIR) region. In particular, the amphiphilic structure enabled M1 to stably anchor onto the cell membrane with low internalization, and its excellent cell-membrane anchoring capacity was hardly affected by cell fixation or permeabilization. The applicability of M1 has also been demonstrated, indicating that the viscosity of tumor cell membranes was higher than that of normal cell membranes, thereby enabling it to effectively distinguish between normal cells and cancer cells. Besides, this probe was applied to visualize the viscosity of both cancer cell membranes and tumors. And the probe was applicable for prolonged imaging of tumors. We believe that M1 may be useful for opening up new avenues for tumor diagnosis at the cell membrane level.