Carbon dots with molecular pores achieve pH-responsive fluorescence by loading L-arginine for intracellular dynamic imaging and scald wound healing

The development of stimuli-responsive fluorescent nanomaterials with molecular pores is crucial for real-time monitoring of the delivery of functional non-fluorescent small molecules. Herein, a new type of yellow emissive porous carbon dots (CDs) derived from 3,9-perylenedicarboxylic acid was synthesized, employing a radical-assisted method under ambient pressure and mild heating conditions, and it is the smallest porous nanoplatform based on CDs. The molecular pores in the CDs can absorb L-arginine via intermolecular hydrogen bonds to form CDs and L-arginine complex (Arg@CDs). The absorbed L-arginine molecules in the molecular pores break the interlayer π – π interactions in the core due to the steric hindrance, leading to a fluorescence color shift from yellow to cyan. When exposed to an acidic environment, the absorbed L-arginine can be released, resulting in a recovery of yellow fluorescence. In vitro, Arg@CDs can be endocytosed by cells and localized to lysosomes, in which the acidic environment causes L-arginine release from the Arg@CDs with a fluorescence color change from cyan to yellow. Thus, Arg@CDs can be used as novel fluorescence color-sensitive pH probe for intracellular dynamic fluorescent imaging. Furthermore, in the mouse scald wound model, intravenous injection of Arg@CDs can significantly accelerate wound healing by promoting macrophage proliferation and anti-inflammatory action.