Ionic liquid mediated organophilic carbon dots for drug delivery and bioimaging

By taking advantage of the structural tunability of ionic liquids (ILs), a series of imidazolium ILs were employed as precursors to prepare carbon dots (IL-CDs) and as regulators to control their properties. The simultaneous formation of hydrophilic CDs (IL-HCDs) and organophilic CDs (IL-OCDs) is achieved in hydrothermal reaction system by undergoing sulfuric acid carbonization. The quantum yields (QY) of IL-OCDs are closely correlated with both the cationic and anionic moieties of the ionic liquids, i.e., longer side chains of cations in the imidazolium ILs and weakly nucleophilic anions tend to produce highly fluorescent IL-OCDs. Both IL-HCDs and IL-OCDs exhibit low cytotoxicity, and that of IL-HCDs is even lower than IL-OCDs. A drug delivery system is constructed by combining anticancer drug curcumin (Cur) with IL-OCDs via hydrophobic interaction, among which 1,3-dibutylimidazolium nitrate derived IL-OCDs exhibit highest photoluminescence. In addition, it serves as a favorable drug carrier with high drug loading efficiency and facilitates rapid penetration/transportation of Cur into the cell interior, which significantly accelerates the apoptosis of HeLa cells. This process is further visualized by cell imaging.