Cellular uptake of PDA–melittin complex to DCs in vivo and in vitro

Cellular uptake of PDA–melittin complex in vitro could be evaluated by detecting the red fluorescence emitted from PDA–melittin nanocomplex in DC cytoplasm. For this, 500 μL (12.5 μg/mL) melittin was incubated with the same volume of PDA nanoparticles (initial concentration is 125 μg/mL) for 30 min. Then the mixture (1 mL) was added to the DCs (1×10⁴ cells/well) at 37°C with 5% CO₂ atmosphere for 1 h. Then the cells were dyed with DAPI (0.1 μg/mL) and the cellular uptake of PDA–melittin complex was observed under a fluorescence microscope. Furthermore, the PDA nanoparticles which were labeled with coumarin were subcutaneously injected into mouse. After 24 h, the draining lymph nodes at the injection site were taken out, completely ground and filtered to obtain a cell suspension. Then the obtained cells were marked with CD11c-PE antibodies and flow cytometry was used to test uptake efficiency of PDA nanoparticles by DCs in vivo.