A Biomimetic Nanoparticle for pDNA Delivery and Expression in Plant Cells in a pH-Dependent Manner

Stimuli-responsive gene delivery vectors based on structural changes triggered by environmental conditions have been widely studied in animals because of their excellent performance in vivo. However, their investigations in plants have lagged behind. Herein, we present a smart gene delivery system based on polyethylenimine (PEI)-modified carbon dots, called amine-functionalized carbon dots (A-CDs), which are pH-responsive, surface charge-switching, and capable of enhancing nuclear import of genes. Due to the amine groups on the surface of A-CDs, the DNA–CD complex has a positive surface charge at pH 5.7, which will facilitate crossing the cell wall and cell membrane. The amine groups in the side chains of the complex can lose protons and promote DNA release in the nucleus in a weakly alkaline environment. Such A-CDs, which mimic the work of nucleosomes, promote an increased accessibility of DNA to complete transcription. In the model plant tobacco, leaves transfected with DNA–CD complexes of green fluorescent protein sequence exhibited distinct green fluorescence under confocal microscopy. This suggests that this smart vector can be used to transiently transfect mature intact plants. Taken together, studies targeting the binding behavior of DNA–CD complexes at different pH values can help to develop more effective gene delivery vector materials.