Synthesis of green carbon dots as bioimaging agent and drug delivery system for enhanced antioxidant and antibacterial efficacy

[Display omitted] •A green carbon dots (CDs) from renewable source was synthesized.•The CDs were used as bioimaging agent.•The CDs were further loaded with a natural flavonoid, Rutin.•The CDs and Rutin-loaded CDs showed excellent antioxidant potential.•The CDs and Rutin-loaded CDs exhibited excellent antibacterial activity.•The CDs and Rutin-loaded CDs exhibited no toxicity to human normal kidney epithelial cells. Now-a-days, synthesis of carbon dots (CDs) from renewable sources has attracted considerable attention due to their wide spread availability, lower cost, higher aqueous solubility and more biocompatibility. Here, we have synthesized water soluble CDs with size between 1 and 4 nm from the root extract of red Korean ginseng via simple microwave irradiation. The CDs showed excitation-dependent fluorescence emission and used as a bioimaging agent. The CDs were further loaded with a natural flavonoid, Rutin to check its efficacy as a drug delivery system. The CDs showed a drug loading content of 12.7 % and a sustained drug release behavior at physiological conditions. CDs showed excellent free radical scavenging activity both in cell free systems and intra-cellular conditions. Besides, loading with the drug further improved the intra-cellular radical scavenging activity. The CDs and the nanohybrids (Rutin-loaded CDs) displayed very little toxicity upto the concentration of 100 μg/mL in normal kidney epithelial cells. The CDs and the nanohybrids also showed a dose-dependent antibacterial effect against both gram negative as well as gram positive bacteria under light exposure as well as dark conditions due to membrane damage. However; under light exposure, the antibacterial activity of CDs and the nanohybrids was further increased due to the production of excessive reactive oxygen species (ROS) and subsequent DNA damage. Overall, our synthesized green CDs can be considered as a promising candidate for the biomedical applications due to its facile synthesis, low cytotoxicity, excellent fluorescent properties and potential as drug delivery systems.