Microwave-Assisted Synthesis of Carbon Dots from Justicia adhatoda Leaves: Evaluation of their Antimicrobial and Cytotoxic Activities

Carbon dots (CDs), as emerging nanomaterials, have garnered significant attention due to their unique optical properties and versatile biomedical applications. In this study, we report a facile and eco-friendly microwave-assisted carbonization method to synthesize fluorescent CDs from Justicia adhatoda leaves, a renewable biomass resource. The resulting CDs exhibited strong fluorescence with an emission peak at 381 nm and a quantum yield of approximately 9.8%, along with excellent water dispersibility and biocompatibility. Morphological analysis revealed an average particle size of approximately 2.08 nm. The antimicrobial potential of these CDs was evaluated against multiple bacterial strains, including Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa, demonstrating dose-dependent broad-spectrum antibacterial activity at 80 µg/mL. Additionally, the CDs showed significant antifungal effects against Candida albicans and Aspergillus niger at comparable concentrations. Cytotoxicity assessment against HepG2 liver cancer cells revealed an IC₅₀ value of 9.69 µg/mL, indicating promising anticancer efficacy. This work highlights the potential of biomass-derived CDs as multifunctional nanomaterials for antibacterial, antifungal, and anticancer applications, advancing their prospects in nanomedicine.