Four novel fluorescent cores bearing a transformable functional group based on a pi-expanded naphthalimide including a fused pyranone or furan ring have been prepared. Fluorescent probes LysoSers 13-16 for lysosomal targeting have been tested.
Co-localization with a commercial lysosome specific marker confirmed that the LysoSers labeled the lysosomal compartment with high selectivity. The LysoSers show excellent brightness and low toxicity.