Spice-based carbon dots: application to in vitro cancer growth inhibition

Synthesis and application of fluorescent carbon dots (C-dots) is emerging as a new alternative to inorganic semiconductor quantum dots due to their high photoluminescence, low photobleaching, high biocompatibility and... [ view full abstract ]

Synthesis and application of fluorescent carbon dots (C-dots) is emerging as a new alternative to inorganic semiconductor quantum dots due to their high photoluminescence, low photobleaching, high biocompatibility and excellent stability in aqueous media. All these features make them excellent candidates in biosensing, bioimaging, biomedical or catalysis applications. Nowadays multiple synthesis techniques are described to obtain C-dots, as well as different carbon sources as alternative for graphite source.1 In fact, natural source materials are being used for production of C-dots due to the simple, cost-effective and environmental friendly syntheses. However, when talking about the toxicity of C-dots, in vitro and in vivo results reported in the literature are inconsistent, and it is considered that the toxicity is mainly determined by the synthesis protocol.2
Therefore, due to the fascinating medicinal properties of certain compounds, in this work four different C-dots have been synthesized from spices including cinnamon, red chilli, turmeric and black pepper, by one-pot green hydrothermal method. They have been characterized with UV-Vis, Fluorescence, FTIR spectroscopies, DLS and TEM.
These C-dots have been evaluated to study their toxicity to in-vitro human normal and cancer cells. Bioimaging studies confirmed that the C-dots inhibited cell viability dose-dependently, showing higher toxicity in cancer cells than in normal cells after 24 h incubation. Particularly, cell viability studies suggested that the growth of human cancer cells is suppressed up to 35%, 50%, 50% and 75%, when using cinnamon, red chilli, turmeric and black pepper respectively, whereas the growth inhibition of normal cells was not significantly affected. Conversely, C-dots synthesized from citric acid did not show any significant toxicity neither in normal nor in cancer cells, which suggests that the anticancer properties observed in the spice-derived C-dots can be attributed to the starting material employed for their fabrication. The interesting anti-cancer activity of the spice-derived C-dots along with the bioimaging applicability and excellent tolerability in normal HK-2 cells, suggests a promising future potential as efficient theranostic agents with minimal side effects in normal cells.
1. S. N. Baker et al., Angew. Chem. Int. Ed. 49 (2010) 6726-6744.
2. P. Pierrat et al., Biomaterials 51 (2015) 290-302.