Ligusticum striatum herb-derived carbon dots (C-dots) were adopted as a drug carrier to deliver methotrexate (MTX). MTX is a folate antagonist drug for chemotherapy of cancer. The MTX was conjugated with C-dots to form the MTX/C-dot complex through non-covalent bonding. The efficiency of drug loading and release of MTX/C-dots was evaluated, showing a high drug loading (85.9%) capability of C-dots. The MTX/C-dots exhibited pH-dependent MTX release behavior in which high efficiency (∼69%) was obtained at pH 5.0 with respect to the value of ∼47% at pH 7.4. The cell viabilities of MTX/C-dots and bare C-dots were evaluated in HeLa and human normal fibroblasts (NHF) cells. The C-dots possess less toxicity, whereas MTX/C-dots showed high cytotoxicity compared to that of bare MTX in HeLa cells. The content of the folate receptor is higher (1.56 times) in HeLa cells than that of NHF cells such that a dense binding between the MTX and folate receptor reduces the cell viability. This finding confirms that the MTX/C-dots had a higher cellular uptake, signifying the excellent drug carrier property of C-dots. In addition, the fluorescence bioimaging measurements were examined in HeLa cells to demonstrate the drug delivery efficacy of MTX/C-dots by using confocal fluorescence microscopy. Accordingly, the MTX/C-dots demonstrate their potential in the bioimaging and drug delivery system resulting from fascinating features including photoluminescence, good biocompatibility, and proficient cellular uptake and drug release. It is believed that the MTX/C-dot nanocarrier might hold great potential for cancer chemotherapeutic applications.
Keywords: Ligusticum striatum; bioimaging; carbon dots; drug carrier; drug delivery; methotrexate.