Synthesis and characterizations of lysosome-targeting morpholine-porphyrin fluorescent probes

Lysosomes play essential role in various intracellular processes. Their malfunction is one of the main causes of diseases such as lysosomal storage diseases, inflammation, and neurodegenerative diseases. Herein, two porphyrin-based fluorescent probes specifically designed for targeting lysosomes were synthesized and characterized. Morpholine, a lysosome targeting molecule, was conjugated to a porphyrin core with and without a spacer (TP_Zn-SM and TP_Zn-M, respectively). Investigation of the photophysical properties and cellular imaging experiments demonstrated that TP_Zn-SM showed optimal lysosome tracking ability for specific imaging in live-cell imaging assays compared to TP_Zn-M. The cytotoxicity of the probes was investigated to evaluate their potential as live-cell fluorescence imaging agents and was found to be minimal. Confocal colocalization studies of the probes with commercial Lysotracker Green in Human Mesenchymal Stem Cells demonstrated the specific localization of the probes in the lysosomes of the cells with a high colocalization coefficient (0.96). Overall, TP_Zn-SM demonstrated better results, which were attributed to the spacers between morpholine and the porphyrin moiety.