Kaempferol-derived carbon dots as antiviral nanomodulators of TLR4 signalling and redox homeostasis in African swine fever virus infection.

Carbon dots (CDs) offer an attractive platform for engineering bioactive nanomaterials, yet converting small natural molecules into antiviral carbon nanostructures with defined nano-bio functions remains underexplored. Here, we report a solvothermal transformation of kaempferol into water-dispersible carbon dots (KPL-CDs) and investigate how this nanoscale conversion reshapes antiviral activity against African swine fever virus (ASFV). Relative to the parent molecule, KPL-CDs exhibit improved aqueous dispersibility, enhanced biocompatibility, and reduced cytotoxicity in primary porcine alveolar macrophages (PAMs). Functionally, KPL-CDs suppress ASFV replication in a dose-dependent manner, accompanied by reduced viral titres, decreased viral particle abundance, and downregulation of ASFV p72 protein and B646L mRNA, the latter encoding p72. Mechanistically, proteomic and biochemical analyses identify the Toll-like receptor 4 (TLR4)/myeloid differentiation primary response 88 (MyD88)/nuclear factor-kappa B (NF-κB) axis as a key host pathway responsive to KPL-CD treatment. KPL-CDs attenuate ASFV-induced inflammatory signalling, reduce TNF-α, IL-1β, IL-6, and IL-18 expression, and simultaneously scavenge intracellular reactive oxygen species (ROS), indicating coupled regulation of inflammatory and redox homeostasis. Molecular docking and biophysical analyses further support direct interaction between KPL-CDs and TLR4, suggesting receptor-level modulation at the nano-bio interface. These findings show that nanoscale transformation of a bioactive flavonoid can generate emergent antiviral function and identify KPL-CDs as a functional carbon nanomaterial for host-directed control of ASFV infection.