Photoluminescent F-doped carbon dots prepared by ring-opening reaction for gene delivery and cell imaging

Carbon dots (CDs) are photoluminescent nanoparticles with distinctive properties, having great potential in nano-biomaterial systems such as gene/drug delivery vectors and cell imaging agents. Fluorine-doped CD C-6F was prepared by a one-step ring-opening polymerization-dehydrative carbonization (RPDC) approach based on low molecular weight polyethyleneimine (PEI, 600 Da) and fluorinated diglycidyl ethers, while the non-fluorinated counterpart C-6H and the CD prepared from PEI 600 Da solely (C-600) were also prepared for comparison. TEM, FT-IR and XPS were performed to determine the compositions and surface states of the CDs. In vitro cell experiment results reveal that the CDs prepared from RPDC approach have much higher transfection efficiency and cellular uptake than PEI 600 contrasts in various cell lines. Compared to non-fluorinated C-6H, C-6F exhibited distinctly higher transfection efficiency, and up to 30 and 260 times higher efficiency than PEI 25 kDa could be achieved in the absence and presence of serum, respectively, indicating the advantage of F-doping. Besides, these CDs exhibit good cell imaging capability under single wavelength excitation, making the materials suitable for cellular tracking and transfection mechanism studies. These results demonstrate that fluorine-doping is an efficient approach to obtained CD gene vectors with high efficiency and serum tolerance.