Microwave-assisted green synthesis of pistachio shell-derived carbon dots for antioxidant, anticancer, and antibacterial applications

Carbon dots (CDs) derived from sustainable precursors offer significant potential for multifunctional biomedical applications. In this study, pistachio shell waste was converted into CDs via a rapid microwave-assisted green synthesis, affording a purified-product mass recovery of 85.0 ± 0.8% after 5 min of microwave irradiation. The obtained nanoparticles (~5 nm) exhibited partial graphitization and oxygen-rich surface functionalities, as confirmed by TEM, FTIR, XPS, and Raman analyses, along with excellent aqueous dispersibility and excitation-dependent blue photoluminescence with a maximum emission at ~450 nm. The CDs showed a fluorescence quantum yield of ~17.2% and an average fluorescence lifetime of ~3.6 ns. Strong antioxidant activity was demonstrated through DPPH and ABTS radical scavenging assays, with IC 50 values of 38.40 ± 0.30 μg/mL and 35.10 ± 0.90 μg/mL, respectively, together with effective suppression of intracellular reactive oxygen species under oxidative stress conditions. Cytotoxicity analysis revealed high biocompatibility toward L929 fibroblasts (>97% viability at 100 μg/mL) and dose-dependent cytotoxicity in Neuro-2a cells, accompanied by mitochondrial membrane depolarization, suggesting an association between the cytotoxic response and altered mitochondrial function. Additionally, the CDs exhibited effective antibacterial activity against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus , as confirmed through MIC, CFU, and antibiofilm assays. Overall, this study demonstrates a rapid and eco-friendly strategy for converting pistachio shell waste into high-value carbon nanomaterials with multifunctional optical and biological properties.