From cell membrane to endoplasmic reticulum: Tunable lipid membrane imaging by regulating the lipophilicity and internalization of carbon dots

The interactions between various organelles play a crucial role on cellular activity, and the design and construction of multi-organelle fluorescent probes is of great challenges. Herein, fluorescent CDs with tunable cell plasma membrane and lipid-rich organelle-targeting ability were fabricated via exquisitely regulating the ratio of tridecanedioic acid and m-diethylaminophenol as the co-precursor, combining the structure–activity relationship to modulate the CDs structure and surficial property. Condensation of m-diethylaminophenol in the presence of different amount of tridecanedioic acid was exploited to construct MCDs and ECDs for targeted cell membrane and endoplasmic reticulum imaging respectively. The appropriately incorporated alkyl chains as membrane anchoring group and the suppressed internalization by carboxyl group led to the retention of MCDs in cell membrane, while the excessive introduction of alkyl chains offered ECDs with high lipophilicity, resulting in the rapid internalization and subsequential distribution in endoplasmic reticulum membrane. The favorable membrane retention capability and excellent photostability make MCDs an excellent probe for long-term targeted-imaging of cell membrane in vitro, with remarkable tracking duration long to five passages and effectively display cell membrane morphological dynamics during cell division and cell death. Moreover, real-time evaluation of cholesterol consumption of Lo phase in cell membrane via ratiometric fluorescence imaging was achieved, attributed to the sensitive response of CDs to polarity variations.