Non-covalent decoration of carbon dots with folic acid via a polymer-assisted strategy for fast and targeted cancer cell fluorescence imaging

An efficient approach for targeting and detecting folate-receptor (FR)-positive cancer cells was developed through non-covalent conjugation of folic acid (FA) on polyethyleneimine modified CDs (PEI-CDs). The fluorescent CDs were prepared by a facile hydrothermal method, and their surfaces were wrapped with positively charged PEI for further conjugation with FA through electrostatic interaction. The FA targeted PEI modified CDs (FA-PEI-CDs) can be used as a turn-on fluorescent nanoprobe for folate receptor (FR)-positive cancer cells in vivo and in vitro. The uptake of the designed FA-PEI-CDs by HeLa and HepG2 cancer cells was verified by confocal laser scanning microscopy after 10 min incubation and competition experiments, as well as a comparative study with FR-negative MCF-7 cells.