Fluorescence Imaging of Mammalian Cells with Cationic Conjugated Polyelectrolytes

Fluorescence imaging using poly(phenylene ethynylene) (PPE) based conjugated polyelectrolytes (CPEs) has garnered considerable attention in the recent past due to their remarkable photophysical properties. In this report, we studied the fluorescence imaging properties of a set of six PPE-based CPEs appended with side chains varying in structure and number of cationic charges. The photophysical and aggregation features of the CPEs depend on the overall charge density on the polymer in water. The cytotoxicity of the CPEs was evaluated against MCF-7 mammalian cells, which revealed that polyelectrolytes with less cationic charge are less cytotoxic andvice versa. Confocal laser scanning microscopy (CLSM) studies showed that all the CPEs could efficiently penetrate into the MCF-7 cells after 10 h of incubation. The transit of CPEs into the lysosomes was confirmed by comparison with the uptake of LysoTracker Red DND-99 dye, which also revealed that the polyelectrolytes are highly photostable. We also demonstrated that the imidazolium-functionalized CPEs could selectively stain bacteria over mammalian cells, suggesting the importance of CPEs for clinical applications.

Automated summary

Fluorescence imaging using PPE-based CPEs has shown remarkable photophysical properties. The overall charge density of CPEs in water affects their photophysical and aggregation features, with less cationic charge leading to lower cytotoxicity. CLSM studies demonstrated efficient penetration of CPEs into MCF-7 cells after 10 hours of incubation.