Green Synthesis of Carbon Dots Derived from Walnut Oil and an Investigation of Their Cytotoxic and Apoptogenic Activities toward Cancer Cells

This paper introduces a green and simple hydrothermal synthesis to prepare carbon quantum dots (CQDs) from walnut oil with a high quantum yield. In addition, cytotoxic and apoptogenic properties of the CQDs were analyzed on human cancer cell lines.
The optical properties and morphological characteristic were investigated by the TEM, XRD, FT-IR, UV-vis and photoluminescence (PL).The cytotoxic potential of walnut CQDs was evaluated on PC3, MCF-7 and HT-29 human carcinoma cell lines using the MTT methods. The mechanism of action was studied by investigating the mode of cell death using the activation of caspase-3 and 9 as well as mitochondrial membrane potential (MMP). Cellular uptake of the CQDs was detected by fluorescence microscope. CQDs had an average size of 12 nm and a significant emission at 420 nm at an excitation wavelength of 350 nm was recorded.
The prepared CQDs possessed a good fluorescent quantum yield of 14.5% with quinine sulfate (quantum yield 54%) as a reference and excellent photo as well as pH stabilities. The walnut CQDs were proved to be an extremely potent cytotoxic agent, especially against MCF-7 and PC-3 cell lines. Induction of apoptosis by CQDs was accompanied by an increase in the activation of caspase-3. Caspase-9 activity did not increase after exposure to the CQDs. Additionally; the MMP did not show any significant loss.
The results of our study can corroborate the cytotoxic and apoptotic effect of walnut CQDs in the PC3 and MCF-7 cancer cell lines.