Synthesis, Spectral Characteristics, and Tumor Imaging of a Fluorescent Small-Molecule Probe Containing Selenium Indole Sulfonate

–Objective: Selenium-containing indole derivatives are widely utilized in biomarker research due to their high fluorescence efficiency, water solubility, and selectivity. However, strategies to enhance their fluorescence stability and biocompatibility remain underdeveloped. Methods: To improve the water solubility and biocompatibility of selenium–indole (Se-In)-based fluorescent small molecules, a sulfonate group was introduced as a hydrophilic moiety. Results and Discussion: A selenium-conjugated molecule was designed to address the issue of fluorescence instability. The optical and physicochemical properties of the resulting probe were evaluated using fluorescence and UV–Vis spectroscopy. The probe exhibited a maximum emission wavelength between 550 and 560 nm and a maximum absorption wavelength at 600 nm. The probe demonstrated favorable spectral properties. Cell imaging experiments confirmed the good biocompatibility of the fluorescent probe with tumor cells across multiple detection channels. This study successfully synthesized Se-In fluorescent small molecules with enhanced fluorescence stability and biocompatibility. Conclusions: The developed probe provides a novel approach for future exploration of selenium-containing indole-based fluorescent molecules.